WO2025239662A1 - Plk1 degradation-inducing compounds for degrader-antibody conjugate - Google Patents

Abstract

The present invention relates to novel PLK1 degradation-inducing compounds for a degrader-antibody conjugate, a preparation method therefor, and a use thereof. The novel PLK1 degradation-inducing compounds, of the present invention, are designed to have a functional group structure capable of being conjugated to antibodies and the like while exhibiting a strong cytotoxic effect on various carcinomas, and thus can be effectively used as a payload drug conjugated to an anticancer degrader-antibody conjugate (DAC).

Description

PLK1 degradation-inducing compounds for degradative drug-antibody conjugates

The present invention relates to a PLK1 degradation-inducing compound that can be utilized in a degrading drug-antibody conjugate, a method for producing the same, and a use thereof.

Antibody-drug conjugates (ADCs) are emerging as a precision anticancer therapeutic platform that utilizes tumor-specific antibodies to selectively deliver highly toxic drugs, thereby selectively killing tumor cells and minimizing side effects on normal cells. One key factor influencing the therapeutic efficacy of these ADCs is the selection of the cytotoxic drug used as the payload. Since the payload must exert toxicity after intracellular delivery and effectively block tumor cell growth, factors such as the target of action, timing of action within the cell cycle, and enzymatic specificity are crucial factors in payload selection.

However, despite some commercial success, traditional strategies using small-molecule compounds as payloads still face challenges, such as the difficulty of these drugs exhibiting sufficient therapeutic activity (therapeutic index) at clinical concentrations and the frequent occurrence of drug resistance. Consequently, there is an unmet need for novel payload drug discovery, and recently, Degrader-Antibody Conjugate (DAC) platforms, which apply targeted protein degradation (TPD) modalities such as Proteolysis-Targeting Chimera (PROTAC) compounds to payload drugs, have emerged as an alternative.

Polo-like kinase 1 (PLK1) is a key regulator of the cell cycle and is overexpressed in tumor cells, making it a key anticancer target in various cancers. However, small-molecule PLK1 inhibitors have failed to achieve sufficient pharmacological efficacy at clinically required concentrations when administered alone or have raised clinical toxicity issues, leading to commercialization failure. Therefore, recent research has focused on developing event-driven, PROTAC-based anticancer agents that target PLK1 and are expected to exhibit sustained efficacy even at low concentrations, moving beyond the occupancy-driven mechanism of traditional inhibitors.

For example, the literature [Mu, Xupeng, et al. Biochemical and biophysical research communications 521.4 (2020): 833-839.] confirmed PLK1 degradation ability and anticancer efficacy in a compound implemented as a PROTAC modality of a PLK1 inhibitor of the dihydropteridone analogue series. However, the linker moiety of the PROTAC compound does not contain a modifiable functional group (amine group, hydroxyl group, etc.) that can be attached to an ADC linker, making it inappropriate to consider as a compound candidate that can be utilized as a payload in DAC.

International Patent Publication No. WO2023/277583 discloses PROTAC compounds based on dihydropteridone analogs, some of which utilize a PROTAC linker containing a functional group capable of modifying an antibody. However, these compounds utilize a thalidomide-like moiety, which is structurally susceptible to in vivo hydrolysis. Furthermore, they only disclose the selective degradation of PLK1, without addressing the payload's key function of potent cytotoxicity.

For a PROTAC compound to be utilized as a DAC payload that induces PLK1 degradation, it is considered that it must satisfy special conditions, such as maintaining PLK1 degradation efficacy, possessing a chemical structure that allows stable conjugation to an ADC linker connected to an antibody, and exhibiting potent cytotoxicity when delivered into tumor cells. However, unlike small-molecule compounds, the structure and behavior of the ternary complex of a multifunctional PROTAC compound are generally known to be very difficult to predict. Therefore, the task of deriving a novel PROTAC compound that satisfies these special conditions is an extremely challenging task.

The purpose of the present invention is to provide a novel PLK1 protein degradation-inducing compound that can be usefully utilized in DAC (Degrader-Antibody Conjugate).

Another object of the present invention is to provide a method for producing and using the PLK1 protein degradation-inducing compound.

To solve the above technical problems, the present invention provides a novel PROTAC compound for inducing PLK1 degradation based on dihydropteridone and glutarimide analogues, which has excellent cytotoxicity as a DAC payload, a method for preparing the same, and a use thereof.

PLK1 degradation-inducing compounds

In one aspect, the present invention provides a novel compound represented by the following chemical formula I:

[Chemical Formula I]

In the above chemical formula I,

R ₁ is methyl, ethyl, isopropyl or cyclopentyl;

R ₂ is methyl or ethyl;

R ₃ is CH, CF, COCH ₃ or N;

R ₄ is H, F, OH, CH ₃ , OCH ₃ , OCH ₂ CH ₂ OH, OCH(CH ₃ ) ₂ OC(CH3) ₃ or O-cyclopentyl;

ULM is a moiety represented by the following chemical formula II-1 or II-2 {wherein, within the moiety represents a covalent bond connecting to L ₁ },

[Chemical Formula II-1]

{In the above chemical formula II-1,

U ₁ is a single bond, -NH-, -O- or -N(CH ₃ )-;

U ₂ is CH, CD or N [wherein D is deuterium];

U ₃ and U ₄ are each independently CH or N;

U ₅ and U ₆ are each independently H, F, CH ₃ , OH or OCH ₃ .

[Chemical Formula II-2]

{In the above chemical formula II-2, U ₇ is CH or N}

L ₁ is a single bond, NH, NHCH ₂ , NHCH ₂ CH ₂ , NHCO or NCO;

L ₂ and L ₄ are each independently cyclohexyl, piperidinyl, piperazinyl, cyclobutyl, azetidinyl, 7-azaspiro[3.5]nonyl, 2,7-diazaspiro[3.5]nonyl, hydroxypiperidinyl, 2-azaspiro[3.3]heptane, spiro[3.3]heptane, 2-azaspiro[3.3]heptane, 2-azaspiro[3.3]heptane, pyrrolidine

and;

L ₃ is a single bond, CH ₂ , NH, N(CH ₃ ), CH ₂ CH ₂ , CH ₂ NH, CH ₂ N(CH ₃ ), NHCH2, N(CH ₃ )CH ₂ or CH ₂ CH ₂ C(=O);

L ₅ is

, , or

{Here, within the above L ₅ represents a covalent bond connecting to L ₄ }.

The compound represented by the above chemical formula I is a bispecific compound implementing a PROTAC (Proteolysis targeting chimera) modality. The compound is characterized by having a structure in which a moiety (PTM) that binds to the target protein PLK1 and an E3 ubiquitin ligase binding moiety (ULM) are connected by a linker molecule. The compound can effectively induce inhibition and degradation of the PLK1 protein by the ubiquitin-proteasome system (UPS) in the cell by positioning the PLK1 protein and E3 ubiquitin ligase in close proximity and inducing artificial ubiquitination of the PLK1 protein.

In the present invention, the PLK-1 protein is an enzyme encoded by the polo-like kinase 1 (PLK1) gene. The sequence of the PLK-1 protein is known in the biotechnology field, and can be referred to, for example, in the literature [NCBI Reference Sequence NP_005021.]. The structure of the PLK1 protein includes an N-terminal serine/threonine kinase domain and a C-terminal repeat of the polo-box domain (PBD), the phosphorylation of which is directly related to the enzymatic activity of PLK1.

The PLK1 protein plays an essential role in mitotic processes in tumor cells, primarily in the G2/M phase cell cycle transition, spindle formation, chromosome alignment, and segregation. It is specifically overexpressed in tumor cells. Due to these biological characteristics, inhibition of PLK1 function can induce cell cycle arrest and apoptosis. Therefore, utilizing PLK1 degraders as payloads in degrader-antibody conjugates (DACs) can be expected to have significant anticancer effects.

In the compound of the present invention, the PLK1 binding moiety (PTM) may be, for example, a moiety having a dihydropteridone-based analog structure, and the definitions of the substituents are as described above.

More specifically, in the compound represented by Chemical Formula I of the present invention, the PTM may be selected from the group consisting of the following moieties, but is not limited thereto.

In the present invention, E3 ubiquitin ligase is a protein that promotes ubiquitin transfer to a target substrate protein, and the ULM moiety described above in the compound of the present invention can bind to CRBN, i.e., Cereblon E3 ubiquitin ligase. CRBN forms an E3 ubiquitin ligase complex together with DDB1, Cul4A, and ROC1, wherein CRBN is a substrate recognition subunit of the complex.

More specifically, in the compound represented by Chemical Formula I of the present invention, ULM may be selected from the group consisting of the following moieties, but is not limited thereto.

[Amendment pursuant to Rule 26 of the Rules 04.06.2025]

The ULM moiety is an E3 ubiquitin ligase binding moiety of the glutarimide family, which offers several important chemical and functional advantages over conventional IMiDs (e.g., thalidomide, lenalidomide, and pomalidomide) in PROTAC design.

The IMiD family of moieties has a two-ring structure consisting of a phthalimide ring and a glutarimide ring, and the phthalimide moiety is vulnerable to degradation by reactive oxygen species (ROS). In addition, IMiDs recruit specific substrates (e.g., IKZF1, IKZF3, CK1α, etc.) after binding to CRBN, and this substrate selectivity can sensitively vary depending on the drug structure, which can lead to unexpected off-target degradation. In addition, IMiDs have limited substitution of the phthalimide ring, and structural modifications can sensitively affect the degradation function. In addition, IMiDs were originally developed as immunomodulatory drugs, so there is a possibility that immune-related side effects may be raised.

In contrast, the glutarimide-based moiety used in the ULM moiety of the present invention is chemically more stable, and thus exhibits superior in vivo metabolic stability, which may be advantageous for improving the pharmacokinetic (PK) profile. Furthermore, it can be designed to recruit CRBN while minimizing off-target substrates, thereby inducing more precise target degradation. Furthermore, N-alkyl substitution or C-position modification is relatively flexible. Therefore, as a DAC payload, it has the advantage of ensuring controllable linker attachment sites and structural diversity while minimizing immune-activating side effects.

In the compound of the present invention, the linker is a group that connects a PLK1 binding moiety (PTM) and an E3 ubiquitin ligase binding moiety (ULM), thereby allowing the E3 ubiquitin ligase protein targeted by the ULM moiety and the PLK1 protein targeted by the PTM moiety to interact with each other within an appropriate physical distance, thereby inducing ubiquitination of the target PLK1 protein. The linker may be, for example, the following moiety, and the definition of the substituent is as described above.

The above linker has a six-membered ring form in which L ₂ and L ₅ are connected in a para-linked form, thereby imparting rigidity to the entire linker molecule. This fixes the relative directionality and distance between the PTM and ULM moieties, thereby forming a ternary complex mediated by the PROTAC compound, and can improve the physicochemical profile of the PROTAC drug, such as contributing to increased drug efficacy by improving metabolic enzyme resistance and increasing intracellular half-life.

In one embodiment, L ₂ in the linker can be selected from the group consisting of the following moieties.

In one embodiment, L ₄ in the linker can be selected from the group consisting of the following moieties.

More specifically, in the compound represented by Chemical Formula I of the present invention, the linker may be selected from the group consisting of the following moieties, but is not limited thereto.

In one embodiment of the present invention, the compound represented by formula I is ULM , and R ₄ may be a compound other than OCH ₂ CH ₂ OH.

In one embodiment of the present invention, the compound represented by formula I is selected from the group consisting of the following compounds.

[Table 1]

The compounds of the present invention may include, in addition to compounds explicitly represented by Formula I, tautomers, optical isomers (including racemic mixtures), specific enantiomers or enantiomerically enriched mixtures thereof.

The compound of the present invention may be in the form of a salt thereof, preferably a pharmaceutically acceptable salt, in addition to the compound explicitly represented by Chemical Formula I. The pharmaceutically acceptable salt refers to any organic or inorganic acid addition salt having a concentration that is relatively non-toxic and harmless to the patient and has an effective effect, and the side effects caused by the salt do not diminish the beneficial effects of the compound represented by Chemical Formula I.

The compounds of the present invention may exist in the form of chimeric molecules conjugated to a functional macromolecule via an additional chemical linker to the compound explicitly represented by Formula I. For example, the macromolecule may be a biomolecule comprising a nucleic acid, an aptamer, a carbohydrate, a peptide or a fragment thereof, or an antibody or a fragment thereof.

Method for preparing a compound that induces PLK1 degradation

The compounds of the present invention can be prepared by synthetic methods known in the field of organic chemistry or by modification techniques apparent to those skilled in the art, for example, by the following reaction schemes 1 to 3.

[Reaction Formula 1]

[Reaction Formula 2]

[Reaction Formula 3]

In the above reaction schemes 1 to 3, PTM, Linker and ULM are the groups defined above or their reactive derivatives, and RG ¹ , RG ² , RG ^2a , RG ^2b , RG ³ , RG ^3a , RG ^3b and RG ⁴ are moieties containing suitable reactive groups capable of linking together PROTAC compound intermediates represented by chemical formula I through covalent bond formation in the field of organic synthesis. The covalent bond formation may be formed through synthetic reactions such as amide formation, ester formation, carbamate formation, urea formation, ether formation, amine formation and various carbon-carbon single bond, double bond formation, click chemistry, etc., depending on the specific reactive group, but is not limited thereto.

In the above reaction scheme, each step may comprise one or multiple synthetic steps. Isolation and purification of the product can be accomplished by standard procedures known to those skilled in the art of organic chemistry.

Uses of PLK1 degradation-inducing compounds

The compound represented by Chemical Formula I of the present invention can induce PLK1 protein degradation. After treating a cell line with an example compound of the present invention, a luciferase assay experiment comparing the PLK1 protein level with that of a control cell line that was not treated with the compound confirmed the effect of inducing degradation of the target protein (Experimental Example 1; Table 2).

The compound represented by Chemical Formula I of the present invention exhibits a potent cancer cell killing effect through PLK1 protein degradation. As a result of an experiment measuring the apoptotic effect after treating PLK1-expressing cancer cells with the example compound of the present invention, it was confirmed that the compound effectively exhibits a cell killing effect in various cancer cells (Experimental Example 2; Tables 3 and 4).

The compounds of the present invention were found to have excellent anti-cancer cell killing effects in a cell killing experiment conducted on lung cancer cell lines (H69, H526) (Table 4). Furthermore, in an experiment measuring the anti-cancer cell killing effects on various cancers, including chronic myelogenous leukemia (K562), Hodgkin's lymphoma (L540), acute monocytic leukemia (THP-1), anaplastic large cell lymphoma (Karpas 299), breast cancer (MCF-7, MDA-MB-468, SK-BR-3), ovarian cancer (SKOV-3), gastric cancer (N87), non-small cell lung cancer (Calu-6), and multiple myeloma (MM1.S), effective anti-cancer cell killing effects were confirmed (Table 5).

Because the compound of the present invention exhibits potent cancer cell killing effects, it can be utilized as a payload for antibody-drug conjugates (ADCs). ADCs enable the delivery of cancer-specific cytotoxic payloads, thereby achieving maximum efficacy in cancer cells while minimizing undesirable effects in non-cancerous cells. Therefore, a degrader-antibody conjugate (DAC) utilizing the PROTAC of the present invention can be a useful strategy for significantly improving the cell permeability and bioavailability shortcomings of PROTAC compounds while also enhancing tissue and cell-type selectivity.

In one embodiment, the invention provides a pharmaceutical composition comprising a PROTAC compound of the invention, wherein the PROTAC compound is conjugated to an antibody or an antigen-binding fragment thereof via an additional linker. The additional linker may be covalently linked to a functional group, such as an amine group, of an ULM of the PROTAC compound or an internal linker of the PROTAC compound. In certain embodiments, the additional linker is a cleavable or non-cleavable linker.

In one embodiment, the present disclosure provides an antibody-drug conjugate comprising an antibody and an antigen-binding fragment thereof and a PROTAC of the present invention, wherein the PROTAC compound is conjugated to the antibody or antigen-binding fragment thereof via a linker.

Because the PROTAC of the present invention eliminates rather than inhibits the target protein, it exhibits superior therapeutic efficacy compared to the small molecule PLK1 inhibitor from which it is derived. Accordingly, the PROTAC of the present invention, particularly when conjugated to a DAC payload, can be utilized for the treatment of PLK1-associated disorders or conditions in which abnormal expression of the PLK1 protein is involved in the onset and/or progression of the disease.

In the present invention, a PLK1-related protein-related disease refers to any disease or condition that can be treated, alleviated, delayed, inhibited, or prevented by inducing degradation or inhibiting the activity of the PLK1 protein, such as cancer. The cancer includes all types of cancer that can exhibit preventive or therapeutic efficacy due to inhibition of the activity of the PLK1 protein. For example, the cancer may be a solid cancer or a blood cancer, and may be at least one selected from the group consisting of squamous cell carcinoma, small cell lung cancer, non-small cell lung cancer, adenocarcinoma of the lung, squamous cell carcinoma of the lung, peritoneal cancer, skin cancer, cutaneous or intraocular melanoma, rectal cancer, anal cancer, esophageal cancer, small intestine cancer, endocrine cancer, parathyroid cancer, adrenal cancer, soft tissue sarcoma, urethral cancer, chronic or acute leukemia, lymphocytic lymphoma, hepatocellular carcinoma, gastric cancer, stomach cancer, pancreatic cancer, glioblastoma, cervical cancer, ovarian cancer, liver cancer, bladder cancer, hepatoma, breast cancer, colon cancer, large intestine cancer, endometrial or uterine cancer, salivary gland cancer, kidney cancer, prostate cancer, vulvar cancer, thyroid cancer, head and neck cancer, brain cancer, and osteosarcoma, but is not limited thereto. The cancer includes not only primary cancer but also metastatic cancer.

The pharmaceutical composition of the present invention can be formulated through a conventional method in the field of pharmaceutical science, and can be administered orally or parenterally depending on the intended method, and the dosage can be determined by taking into consideration the patient's weight, age, sex, health condition, diet, administration time, administration method, excretion rate, and severity of the disease.

The compounds of the present invention can be used to degrade PLK1 protein in a sample by treating the sample in vivo or in vitro. The sample may be a cell, cell culture, or a bodily fluid or tissue of a mammal, including a human. The method can be used for diagnostic or therapeutic purposes.

The present invention provides a method for preventing or treating a PLK1 protein-related disease, comprising administering to a patient a therapeutically effective amount of a compound represented by Chemical Formula I, preferably conjugated to a payload of DAC. The PLK1 protein-related disease includes cancer.

The novel PLK1 degradation-inducing compound of the present invention has a high cell killing effect on various cancers, and thus can be usefully utilized as a payload conjugated to a degrader-antibody conjugate (DAC) for PLK1-related diseases.

Hereinafter, the composition and effects of the present invention will be described in more detail through examples and experimental examples. These examples and experimental examples are intended solely to illustrate the present invention and are not intended to limit the scope of the present invention. All references cited throughout this application are expressly incorporated herein by reference in their entirety.

Specific example compounds of the present invention were synthesized according to the following manufacturing method and their structures were analyzed.

analytical instrument

LCMS: Shimadzu LC-20AD & LCMS 2020, Agilent Single Quad system (1260)

NMR: BRUKER AVANCE ², BRUKER Advance Nanobay 400MHz

HPLC: Shimadzu model-LC-20AB/AD system, Agilent 1260 II LC

SFC: SHIMADZU LC-30ADsf

LCMS analysis method

LCMS data were recorded on a Shimadzu LC-20AD system equipped with an electron spray ionization (ESI) LCMS 2020 or an Agilent Single Quad system (1260). 0.04% TFA in water (solvent A) and 0.02% TFA in acetonitrile (solvent B) were used as mobile phases. Alternatively, 0.025% NH ₃ · H ₂ O in water (solvent A) and acetonitrile (solvent B) were used as mobile phases. HALO C18 (3.0X30mm, 5um, 5.0um), XPtC-C18 (2.1X30mm, 5.0um), or Kinetex EVO C13 (2.1*30mm, 5.0um) columns were used.

HPLC analysis method

HPLC was performed using a Shimadzu model-LC-20AB/AD system or an Agilent 1260 II LC, with 0.04% TFA in water (solvent A) and 0.02% TFA in acetonitrile (solvent B) as mobile phases. The columns used were Kinetex C18 (4.6X50mm, 5um), HALO C18 (3.0X100mm, 2.7um), or Unison UK C18 (4.6X150mm, 3.0um).

NMR analysis method

¹ H NMR spectra were recorded with a BRUKER AVANCE ²/5mm Probe (BBO) or BRUKER Advance Nanobay 400MHz/ 5mm Probe (BBO).

SFC analysis method

SFC was performed on a SHIMADZU LC-30ADsf with mobile phases of _CO2 (solvent A) and 0.05% DEA in isopropanol (solvent B) or 0.05% DEA in ethanol and ACN (solvent B). The columns used were Chiralpak IK-3 50Х4.6 mm, 3 μm or Chiralpak AD-3 50Х4.6 mm, 3 μm or (S,S)Whelk-O1 50Х4.6 mm, 3.5 μm.

<Example>

Example 1. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 1)

Step 1. Synthesis of (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoic acid (3)

To a solution of (R)-2-chloro-8-cyclopentyl-5,7-dimethyl-7,8-dihydropteridin-6(5H)-one (1 g, 3.56 mmol) and 4-amino-3-methoxybenzoic acid (893 mg, 5.34 mmol) in ethanol (5 mL) and water (20 mL) was added hydrochloric acid (12 M, 1.19 mL), and the mixture was stirred at 100 °C for 14 h. LC-MS analysis revealed a peak of the target mass (53%). The reaction mixture was filtered, and the filter cake was washed with water (10 mL). The filter cake was collected and dried under reduced pressure to give the title compound (1.27 g, crude) as a white solid. MS(M+H) ⁺ = 412.2

Step 2. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 1)

To a solution of (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoic acid (260 mg, 631.91 μmol) and HATU (264.30 mg, 695.10 μmol) in DMF (6 mL) was added DIPEA (816.69 mg, 6.32 mmol, 1.10 mL), and the mixture was stirred at 15 °C for 15 min. Afterwards, a solution of 3-(4-(((1-((1r,4r)-4-aminocyclohexyl)piperidin-4-yl)methyl)amino)phenyl)piperidine-2,6-dione (340 mg, 663.33 μmol, TFA salt) in DMF (6 mL) was added at 0 °C, and the mixture was stirred again at 15 °C for 3 h. LCMS analysis showed the peak of the target mass (71%). The mixture was diluted with EtOAc (10 mL) and saturated NaHCO ₃ (10 mL), and extracted with DCM (20 mL x 3). The organic layer was washed with saturated NaHCO ₃ (20 mL x 2), dried over Na ₂ SO ₄, and filtered. The filtrate was concentrated under reduced pressure. The product was purified by prep-HPLC (column: Waters Xbridge C18 150*50 mm* 10um; mobile phase: [water (NH ₄ HCO ₃ ) - ACN]; gradient: 31% - 61% B over 10 min), and the eluate was lyophilized to obtain the title compound as a white solid (205.42 mg, 246.41 μmol, yield 38.99%, purity 95%). MS(M+H) ⁺ = 792.6

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.72 (s, 1H), 8.43 - 8.37 (m, 1H), 8.02 (br d, J = 7.9 Hz, 1H), 7.89 (s, 1H), 7.62 (s, 1H), 7.49 - 7.42 (m, 2H), 6.88 (d, J = 8.6 Hz, 2H), 6.51 (d, J = 8.6 Hz, 2H), 5.57 (br t, J = 5.6 Hz, 1H), 4.49 - 4.37 (m, 1H), 4.32 (q, J = 6.7 Hz, 1H), 3.93 (s, 3H), 3.77 - 3.67 (m, 1H), 3.62 (dd, J = 5.1, 10.4 Hz, 1H), 3.23 (s, 3H), 2.90 - 2.80 (m, 4H), 2.64 - 2.55 (m, 1H), 2.47 - 2.39 (m, 1H), 2.15 (br t, J = 10.9 Hz, 2H), 2.09 - 1.85 (m, 6H), 1.84 - 1.70 (m, 8H), 1.66 - 1.57 (m, 2H), 1.53 - 1.44 (m, 1H), 1.43 - 1.28 (m, 4H), 1.23 (d, J = 6.7 Hz, 3H), 1.19 - 1.07 (m, 2H).

Example 2. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1s,4S)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 2)

Step 1. Synthesis of tert-butyl ((1s,4s)-4-(4-(methoxymethylene)piperidin-1-yl)cyclohexyl)carbamate (2)

To a solution of tert-butyl ((1s,4s)-4-(4-oxopiperidin-1-yl)cyclohexyl)carbamate (0.5 g, 1.69 mmol) and dimethyl (1-diazo-2-oxopropyl)phosphonate (818.67 mg, 4.22 mmol) in methanol (10 mL) was added K ₂ CO₃ (582.84 mg, 4.22 mmol) at 0 °C, and the mixture was stirred at 0 °C for 0.5 h. Then, the temperature was increased to 20 °C and stirred for an additional 16 h. LCMS analysis confirmed the peak of the target mass. The reaction mixture was quenched with saturated NH ₄ Cl (50 mL) and extracted with EtOAc (50 mL Х 2). The organic layer was dried over Na ₂ SO₄ and filtered. The filtrate was concentrated under reduced pressure to obtain the title compound (0.6 g, crude) as a yellow oil. MS(M+H) ⁺ = 325.3

Step 2. Synthesis of tert-butyl ((1s,4s)-4-(4-formylpiperidin-1-yl)cyclohexyl)carbamate (3)

To a solution of tert-butyl ((1s,4s)-4-(4-(methoxymethylene)piperidin-1-yl)cyclohexyl)carbamate (0.6 g, 1.85 mmol) in acetone (15 mL) were added TsOH (477.66 mg, 2.77 mmol) and H ₂ O (200.00 mg, 11.10 mmol, 0.2 mL), and the mixture was stirred at 20 °C for 3 h. LCMS analysis confirmed the peak of the target mass. The mixture was diluted with EtOAc (30 mL) and saturated Na ₂ CO₃ (20 mL), and the organic layer was dried over Na ₂ SO₄ and filtered. The filtrate was concentrated under reduced pressure to give the title compound (0.37 g, crude) as a yellow oil. MS(M+H) ⁺ = 311.3

Step 3. Synthesis of tert-butyl ((1s,4s)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)carbamate (4)

To a solution of tert-butyl ((1s,4s)-4-(4-formylpiperidin-1-yl)cyclohexyl)carbamate (370 mg, 1.19 mmol) and 3-(4-aminophenyl)piperidine-2,6-dione (244 mg, 1.19 mmol) in DCM (6 mL) and DMF (3 mL) was added AcOH (146.86 mg, 2.45 mmol, 140 μL), and the mixture was stirred at 20 °C for 0.5 h. Then, NaBH(OAc) ₃ (758 mg, 0.58 mmol) was added, and the mixture was further stirred at 20 °C for 0.5 h. LCMS analysis confirmed the peak of the target mass. Water (10 mL) was added to the reaction mixture, and the pH was adjusted to 9 with saturated Na ₂ CO₃. The mixture was extracted with DCM (30 mL X 2). The combined organic layers were washed with water (10 mL), dried over Na ₂ SO ₄, and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (12 g SepaFlash® column, 10–20% MeOH/EtOAc gradient @ 200 mL/min) to give the title compound as a yellow solid (0.2 g, 401.08 μmol, yield 33.65%). MS (M+H) ⁺ = 499.4

Step 4. Synthesis of 3-(4-(((1-((1s,4s)-4-aminocyclohexyl)piperidin-4-yl)methyl)amino)phenyl)piperidine-2,6-dione (5)

To a solution of tert-butyl ((1s,4s)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)carbamate (0.1 g, 200.54 μmol) in DCM (1 mL) was added TFA (460.50 mg, 4.04 mmol, 0.3 mL), and the mixture was stirred at 20 °C for 1 h. The mixture was concentrated under reduced pressure to obtain the title compound (0.1 g, crude, TFA salt) as a yellow oil.

Step 5. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1s,4S)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 2)

The title compound (28.4 mg, 34.78 μmol, yield 20.45%, purity 97%) was obtained as a white solid by a similar method to step 2 of compound 1. MS(M+H) ⁺ = 792.6

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.73 (s, 1H), 8.41 (d, J = 8.3 Hz, 1H), 7.99 (br d, J = 7.1 Hz, 1H), 7.89 (s, 1H), 7.62 (s, 1H), 7.53 - 7.46 (m, 2H), 6.88 (d, J = 8.3 Hz, 2H), 6.51 (d, J = 8.4 Hz, 2H), 5.64 - 5.53 (m, 1H), 4.48 - 4.37 (m, 1H), 4.32 (q, J = 6.6 Hz, 1H), 3.99 - 3.86 (m, 4H), 3.62 (dd, J = 5.0, 10.5 Hz, 1H), 3.23 (s, 3H), 3.01 (br d, J = 9.9 Hz, 2H), 2.87 (br t, J = 5.9 Hz, 2H), 2.65 - 2.55 (m, 1H), 2.44 (td, J = 4.6, 17.1 Hz, 1H), 2.18 - 1.85 (m, 9H), 1.84 - 1.69 (m, 8H), 1.67 - 1.40 (m, 7H), 1.29 - 1.10 (m, 5H).

Example 3. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-(2-hydroxyethoxy)benzamide (Compound 3)

Step 1. Synthesis of methyl (R)-3-(2-((tert-butyldimethylsilyl)oxy)ethoxy)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)benzoate (3)

To a solution of (R)-2-chloro-8-cyclopentyl-5,7-dimethyl-7,8-dihydropteridin-6(5H)-one (790 mg, 2.81 mmol), methyl 4-amino-3-(2-((tert-butyldimethylsilyl)oxy)ethoxy)benzoate (1 g, 3.07 mmol) and K ₃ PO ₄ (1.79 g, 8.44 mmol) in dioxane (20 mL) were added Pd ₂ (dba) ₃ (51.53 mg, 56.28 μmol) and Xantphos (48.84 mg, 84.42 μmol) under N ₂ , and the mixture was stirred at 100 °C for 14 h. LCMS confirmed the remaining starting material, Xantphos (162.82 mg, 281.39 μmol) and Pd ₂ (dba) ₃ (515.34 mg, 562.77 μmol) were added, and the reaction mixture was stirred again at 100 °C under CN ₂ for 14 h. LCMS showed a peak with the desired mass (37%). The mixture was filtered, and the filter cake was washed with EtOAc (50 mL). The filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (12 g SepaFlash® silica flash column, eluent of 40–60% EtOAc/Petroleum ether gradient @ 100 mL/min) followed by flash silica gel chromatography (12 g SepaFlash® silica flash column, eluent of 30–45% EtOAc/Petroleum ether gradient @ 100 mL/min) to give the title compound (930 mg, 1.63 mmol, 58.01% yield) as a yellow oil. MS (M+H) ⁺ = 570.4

Step 2. Synthesis of (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-(2-hydroxyethoxy)benzoic acid (4)

To a solution of methyl (R)-3-(2-((tert-butyldimethylsilyl)oxy)ethoxy)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)benzoate (930 mg, 1.63 mmol) in THF (6 mL) and MeOH (6 mL) was added NaOH (2 M, 3.28 mL), and the mixture was stirred at 15 °C for 14 h. When LCMS confirmed that the starting material remained, NaOH (2 M, 1.64 mL) was added, and the mixture was stirred at 15 °C for 2 h. The desired mass peak (74%) was obtained by LCMS. The mixture was concentrated under reduced pressure, and the product was diluted with THF (30 mL) and 12 N HCl (1 mL). The suspension was concentrated under reduced pressure to obtain the title compound (1.4 g, crude) as a yellow solid. MS(M+H) ⁺ = 442.2

Step 3. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-(2-hydroxyethoxy)benzamide (Compound 3)

To a solution of (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-(2-hydroxyethoxy)benzoic acid (425 mg, 962.67 μmol) and HATU (215.13 mg, 565.78 μmol) in DMF (6 mL) was added DIPEA (742.00 mg, 5.74 mmol, 1 mL), and the mixture was stirred at 15 °C for 15 min. Afterwards, a solution of 3-(4-(((1-((1r,4r)-4-aminocyclohexyl)piperidin-4-yl)methyl)amino)phenyl)piperidine-2,6-dione (290 mg, 565.78 μmol, TFA salt) in DMF (6 mL) was added at 0 °C, and the mixture was stirred at 15 °C for 1 h. A peak with the desired mass was identified by LCMS. The mixture was diluted with EtOAc (10 mL) and saturated NaHCO ₃ (10 mL), and extracted with DCM (10 mL x 3). The combined organic layer was washed with saturated NaHCO ₃ (20 mL), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure. The product was purified by prep-HPLC (column: Waters Xbridge C18 150*50 mm* 10um; mobile phase: [water (NH ₄ HCO ₃ ) -ACN]; gradient: 23%-53% B over 10 min), and the eluate was lyophilized to obtain the title compound (138.51 mg, 160.08 μmol, 28.29% yield, 95% purity) as a yellow solid. MS(M+H) ⁺ =822.6

SFC Method details: "Column: Chiralpak AD-3 50Х4.6mm ID, 3um Mobile phase: Phase A for CO ₂ , and Phase B for MeOH+ACN (0.05%DEA); Gradient elution: 60% MeOH +ACN (0.05% DEA) in CO ₂ Flow rate: 3mL/min;Detector: PDA Column Temp: 35C;Back Pressure: 100Bar"

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.72 (s, 1H), 8.42 (d, J = 8.9 Hz, 1H), 8.04 (s, 1H), 8.00 (br d, J = 7.7 Hz, 1H), 7.90 (s, 1H), 7.49 - 7.42 (m, 2H), 6.88 (d, J = 8.4 Hz, 2H), 6.50 (d, J = 8.6 Hz, 2H), 5.56 (t, J = 5.5 Hz, 1H), 5.16 (t, J = 5.8 Hz, 1H), 4.47 - 4.38 (m, 1H), 4.32 (q, J = 6.8 Hz, 1H), 4.11 (t, J = 4.5 Hz, 2H), 3.85 - 3.76 (m, 2H), 3.74 - 3.67 (m, 1H), 3.62 (dd, J = 5.1, 10.3 Hz, 1H), 3.24 (s, 3H), 2.89 - 2.79 (m, 4H), 2.64 - 2.55 (m, 1H), 2.48 - 2.39 (m, 1H), 2.31 - 2.22 (m, 1H), 2.15 (br t, J = 11.6 Hz, 2H), 2.10 - 1.96 (m, 3H), 1.94 - 1.69 (m, 11H), 1.66 - 1.55 (m, 2H), 1.52 - 1.42 (m, 1H), 1.41 - 1.26 (m, 4H), 1.23 (d, J = 6.7 Hz, 3H), 1.19 - 1.07 (m, 2H).

Example 4. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)benzamide (Compound 4)

Step 1. Synthesis of (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)benzoic acid (3)

To a solution of (R)-2-chloro-8-cyclopentyl-5,7-dimethyl-7,8-dihydropteridin-6(5H)-one (100 mg, 356.19 μmol) in EtOH (0.5 mL) was added a solution of 4-aminobenzoic acid (80 mg, 583.36 μmol) and HCl (12 M, 120 μL) in H ₂ O (3 mL) at 20°C. The mixture was stirred at 100°C for 16 h. The desired mass peak (77%) was identified by LCMS. The reaction mixture was stirred for another 1 h at 20°C, and then the mixture was filtered. The filter cake was dried under reduced pressure to obtain the title compound (100 mg, crude) as a pale yellow solid.

MS (M+H) ⁺ = 382.2

Step 2. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)benzamide (Compound 4)

The title compound (19.3 mg, 22.80 μmol, yield 12.42%, purity 90%) was obtained as a white solid by a similar method to step 2 of Example 1. MS (M+H) ⁺ = 762.5

^1H NMR (400 MHz, DMSO _- d6 ) δ = 10.78 (s, 1H), 9.35 (s, 1H), 8.01 - 7.87 (m, 2H), 7.83 - 7.68 (m, 4H), 6.87 (d, J = 8.4 Hz, 2H), 6.50 (d, J = 8.4 Hz, 2H), 5.60 - 5.51 (m, 1H), 4.55 - 4.39 (m, 1H), 4.31 (q, J = 6.6 Hz, 1H), 3.74 - 3.58 (m, 2H), 3.23 (s, 3H), 2.96 - 2.75 (m, 4H), 2.67 - 2.54 (m, 1H), 2.46 - 2.39 (m, 1H), 2.30 - 2.20 (m, 1H), 2.19 - 1.92 (m, 6H), 1.90 - 1.82 (m, 2H), 1.81 - 1.67 (m, 8H), 1.65 - 1.46 (m, 3H), 1.40 - 1.27 (m, 4H), 1.21 (d, J = 6.7 Hz, 3H), 1.17 - 1.06 (m, 2H)

Example 5. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-fluorobenzamide (Compound 5)

Step 1. Synthesis of (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-fluorobenzoic acid (3)

To a solution of (R)-2-chloro-8-cyclopentyl-5,7-dimethyl-7,8-dihydropteridin-6(5H)-one (100 mg, 356.19 μmol) in EtOH (0.5 mL) was added 4-amino-3-fluorobenzoic acid (90 mg, 580.17 μmol) and a solution of HCl (12 M, 120 μL) in H ₂ O (3 mL) at 20 °C. The mixture was stirred at 100 °C for 16 h. LCMS analysis revealed that the desired mass peak was detected at 41%. The reaction mixture was stirred for another 1 h at 20 °C, filtered, and the filter cake concentrated under reduced pressure to give the title compound (80 mg, crude) as a pale yellow solid. MS (M+H) ⁺ = 400.2.

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.17 (s, 1H), 7.96 - 7.90 (m, 1H), 7.87 (s, 1H), 7.84 - 7.75 (m, 2H), 4.49 (q, J = 6.8 Hz, 1H), 4.23 - 4.14 (m, 1H), 3.21 (s, 3H), 1.91 - 1.76 (m, 4H), 1.47 - 1.35 (m, 7H)

Step 2. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-fluorobenzamide (Compound 5)

The title compound (29.7 mg, 35.79 μmol, yield 20.42%, purity 94%) was obtained as a white solid by a similar method to step 2 of Example 1. MS (M+H) ⁺ = 780.5

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.75 (s, 1H), 8.61 (s, 1H), 8.18 - 8.07 (m, 2H), 7.87 (s, 1H), 7.74 - 7.61 (m, 2H), 6.89 (d, J = 8.4 Hz, 2H), 6.51 (d, J = 8.4 Hz, 2H), 5.64 - 5.53 (m, 1H), 4.38 - 4.26 (m, 2H), 3.74 - 3.59 (m, 2H), 3.23 (s, 3H), 2.94 - 2.79 (m, 4H), 2.66 - 2.56 (m, 1H), 2.48 - 2.42 (m, 1H), 2.32 - 2.24 (m, 1H), 2.18 - 1.93 (m, 5H), 1.92 - 1.83 (m, 3H), 1.82 - 1.66 (m, 8H), 1.56 - 1.45 (m, 3H), 1.40 - 1.29 (m, 4H), 1.22 (d, J = 6.7 Hz, 3H), 1.17 - 1.07 (m, 2H)

Example 6. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-hydroxybenzamide (Compound 6)

Step 1. Synthesis of (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-hydroxybenzoic acid (3)

The title compound (80 mg, crude) was obtained as a pale yellow solid by a similar method to step 1 of Example 5. MS(M+H) ⁺ = 398.2.

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.68 (br s, 1H), 9.52 - 9.41 (m, 1H), 7.99 - 7.83 (m, 2H), 7.55 (d, J = 1.8 Hz, 1H), 7.47 - 7.41 (m, 1H), 4.51 (q, J = 6.7 Hz, 1H), 4.36 - 4.24 (m, 1H), 3.20 (s, 3H), 2.02 - 1.78 (m, 4H), 1.68 - 1.45 (m, 4H), 1.44 - 1.35 (m, 3H).

Step 2. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-hydroxybenzamide (Compound 6)

To a solution of (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-hydroxybenzoic acid (60 mg, 150.97 μmol) in DMF (2 mL) were added EDCI (60 mg, 312.99 μmol), HOBt (40.80 mg, 301.94 μmol), and 3-(4-(((1-((1r,4r)-4-aminocyclohexyl)piperidin-4-yl)methyl)amino)phenyl)piperidine-2,6-dione (70 mg, 136.57 μmol, TFA) at 20 °C. After that, DIPEA (190.80 mg, 1.48 mmol, 257.14 μL) was added dropwise at 0 °C, and the mixture was stirred at 20 °C for 16 h. LCMS analysis detected a peak with the desired mass. The reaction mixture was diluted with H ₂ O (10 mL) and extracted with EtOAc (30 mL X 2). The combined organic layer was washed with brine (20 mL X 3), dried over Na ₂ SO ₄, and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by prep-HPLC (column: Waters xbridge 150 x 25 mm 10 μm; mobile phase: [H ₂ O (10 mM NH ₄ HCO ₃ ) - ACN]; gradient: 40% - 60% B over 8.0 min, column Temp: 30 °C) and repurified by prep-HPLC (column: Phenomenex Luna C18 150 x 25 mm x 10 μm; mobile phase: [H ₂ O (0.1% TFA) - ACN]; gradient: 0% - 25% B over 15.0 min, column Temp: 30 °C). The eluate was lyophilized to obtain the title compound (2.2 mg, 2.44 μmol, 1.62% yield, 99% purity, TFA) as a pale yellow solid. MS(M+H) ⁺ = 778.5

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.76 (s, 1H), 9.01 - 8.87 (m, 1H), 8.23 - 8.11 (m, 1H), 7.95 - 7.85 (m, 1H), 7.81 (s, 1H), 7.41 (d, J = 1.5 Hz, 1H), 7.37 - 7.31 (m, 1H), 6.92 (d, J = 8.4 Hz, 2H), 6.55 (d, J = 8.6 Hz, 2H), 4.51 - 4.41 (m, 1H), 4.37 - 4.28 (m, 1H), 3.68 - 3.60 (m, 4H), 3.53 - 3.44 (m, 3H), 3.30 - 3.13 (m, 5H), 3.04 - 2.87 (m, 4H), 2.67 - 2.58 (m, 1H), 2.47 - 2.43 (m, 1H), 2.10 - 1.94 (m, 8H), 1.92 - 1.78 (m, 4H), 1.72 - 1.48 (m, 6H), 1.46 - 1.38 (m, 3H), 1.37 - 1.30 (m, 3H).

Example 7. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-methylbenzamide (Compound 7)

Step 1. Synthesis of (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methylbenzoic acid (3)

The title compound (60 mg, crude) was obtained as a pale yellow solid by a similar method to step 1 of Example 5. MS(M+H) ⁺ = 396.2.

Step 2. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-methylbenzamide (Compound 7)

The title compound (43.1 mg, 51.65 μmol, yield 29.18%, purity 93%) was obtained as a white solid by a similar method to step 2 of Example 1. MS(M+H) ⁺ = 776.6

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.72 (s, 1H), 8.15 (s, 1H), 8.04 - 7.96 (m, 1H), 7.85 - 7.79 (m, 2H), 7.67 (s, 1H), 7.64 - 7.58 (m, 1H), 6.92 - 6.84 (m, 2H), 6.54 - 6.45 (m, 2H), 5.63 - 5.55 (m, 1H), 4.37 - 4.24 (m, 2H), 3.74 - 3.60 (m, 2H), 3.22 (s, 3H), 2.90 - 2.82 (m, 4H), 2.60 - 2.55 (m, 1H), 2.46 - 2.43 (m, 1H), 2.31 - 2.23 (m, 4H), 2.19 - 2.01 (m, 4H), 1.94 - 1.84 (m, 4H), 1.81 - 1.69 (m, 6H), 1.68 - 1.60 (m, 2H), 1.53 - 1.44 (m, 3H), 1.40 - 1.28 (m, 4H), 1.23 - 1.18 (m, 3H), 1.18 - 1.07 (m, 2H)

Example 8. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-2-fluoro-5-methoxybenzamide (Compound 8)

Step 1. Synthesis of 2-fluoro-5-hydroxy-4-nitrobenzoic acid (2)

2,5-Difluoro-4-nitrobenzoic acid (5 g, 24.62 mmol) was added to a solution of KOH (13.81 g, 46.18 mmol) in H ₂ O (100 mL), and the resulting mixture was stirred at 80 °C for 5 h. The pH of the mixture was adjusted to pH = 3 using 12 M HCl, and the resulting suspension was filtered, and the filter cake was collected and dried to obtain the title compound (4.5 g, 22.38 mmol, yield 90.89%) as a yellow solid.

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 11.36 (s, 1H), 7.90 (d, J = 9.9 Hz, 1H), 7.55 (d, J = 6.1 Hz, 1H).

Step 2. Synthesis of methyl 2-fluoro-5-methoxy-4-nitrobenzoic acid (3)

To a solution of 2-fluoro-5-hydroxy-4-nitrobenzoic acid (4.5 g, 22.38 mmol) in DMF (50 mL) were added K ₂ CO₃ (15 g, 108.53 mmol) and MeI (7.98 g, 56.22 mmol, 3.5 mL), and the mixture was stirred at 20 °C for 16 h. LCMS confirmed that the starting material was consumed. The mixture was diluted with H ₂ O (200 mL), extracted with EtOAc (100 mL Х 3), and the combined organic layers were washed with brine (200 mL), dried over Na ₂ SO₄, and filtered. The filtrate was concentrated under reduced pressure to give the title compound (2.6 g, 11.35 mmol, yield 50.70%) as a yellow solid.

Step 3. Synthesis of methyl 4-amino-2-fluoro-5-methoxybenzoic acid (4)

To a solution of methyl 2-fluoro-5-methoxy-4-nitrobenzoic acid (2.6 g, 11.35 mmol) in EtOH (30 mL) and H ₂ O (6 mL) were added Fe (3.17 g, 56.73 mmol) and NH ₄ Cl (3.03 g, 56.73 mmol), and the resulting mixture was stirred at 80 °C for 1 h. The main peak of the target mass was observed in LCMS analysis. The reaction mixture was concentrated under reduced pressure, and to the residue were added EtOAc (50 mL) and H ₂ O (50 mL), and the pH was adjusted to 8 with saturated Na ₂ CO₃ solution. After filtering the mixture, the filter cake was washed with EtOAc (50 mL), the filtrate was extracted again with EtOAc (50 mL Х 3), the combined organic layers were washed with H ₂ O (100 mL), dried over Na ₂ SO 4, and filtered. The filtrate was concentrated under reduced pressure to obtain the title compound (2.1 g, 10.54 mmol, yield 92.93%) as a yellow solid. MS (M+H) ⁺ = 199.9

Step 4. Synthesis of methyl (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-2-fluoro-5-methoxybenzoic acid (5)

To a solution of (R) _-2 -chloro-8-cyclopentyl-5,7-dimethyl-7,8-dihydropteridin-6(5H)-one (150 mg, 534.28 μmol) and methyl 4-amino-2-fluoro-5-methoxybenzoic acid (106.42 mg, 534.28 μmol) in H2O (4 mL) and EtOH (1 mL) was added HCl (12 M, 89.05 μL), and the mixture was stirred at 100 °C for 16 h. A peak of the target mass (45%) was observed by LCMS. The mixture was filtered at 20 °C, and the filter cake was collected and dried to give the title compound (150 mg, 338.24 μmol, yield 63.31%) as a white solid. MS (M+H) ⁺ = 444.2

Step 5. Synthesis of (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-2-fluoro-5-methoxybenzoic acid (Compound 6)

To a solution of methyl (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-2-fluoro-5-methoxybenzoic acid (150 mg, 338.24 μmol) in THF (1 mL) and MeOH (1 mL) was added NaOH (2 M, 845.60 μL), and the mixture was stirred at 25 °C for 14 h. The peak of the target mass (79%) was observed by LCMS. The mixture was concentrated under reduced pressure to remove the solvent, and H ₂ O (10 mL) was added to the residue, and the pH was adjusted to < 3 with HCl (12 M). The resulting mixture was filtered, and the filter cake was washed with H ₂ O (10 mL). The filter cake was collected and dried to obtain the title compound as a white solid (100 mg, 32.86 μmol, yield 68.84%). MS (M+H)+ = 430.2

Step 6. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-2-fluoro-5-methoxybenzamide (Compound 8)

The title compound (39.9 mg, 48.77 μmol, yield 41.89%, purity 99%) was obtained as a white solid by a similar method to step 2 of Example 1. MS(M+H) ⁺ = 810.4

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.74 (s, 1H), 8.38 (d, J = 13.6 Hz, 1H), 7.94 (s, 1H), 7.72 (s, 1H), 7.38 - 7.25 (m, 1H), 7.17 (d, J = 6.7 Hz, 1H), 6.91 (d, J = 8.3 Hz, 2H), 6.54 (d, J = 8.1 Hz, 2H), 5.92 - 5.53 (m, 1H), 4.49 - 4.42 (m, 1H), 4.35 (q, J = 6.7 Hz, 1H), 3.92 (s, 3H), 3.79 - 3.69 (m, 1H), 3.64 (dd, J = 4.9, 10.4 Hz, 1H), 3.50 - 3.41 (m, 1H), 3.24 (s, 3H), 3.04 - 2.81 (m, 4H), 2.69 - 2.57 (m, 2H), 2.49 - 2.40 (m, 2H), 2.10 - 1.90 (m, 10H), 1.85 - 1.76 (m, 6H), 1.69 - 1.61 (m, 3H), 1.45 - 1.31 (m, 4H), 1.24 (d, J = 6.7 Hz, 3H).

Example 9. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-2-fluoro-5-(2-hydroxyethoxy)benzamide (Compound 9)

Step 1. Synthesis of 2-fluoro-5-hydroxy-4-nitrobenzoic acid (2)

A solution of 2,5-difluoro-4-nitrobenzoic acid (5 g, 24.62 mmol) in KOH (4 M, 84 mL) was stirred at 50 °C for 14 h. The target mass was confirmed by LCMS. The mixture was adjusted to pH = 3 with 12 N HCl and filtered. The filter cake was collected and dried under reduced pressure to obtain the title compound (5 g, crude) as a yellow solid.

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 7.72 (d, J = 9.6 Hz, 1H), 7.35 (d, J = 6.0 Hz, 1H)

Step 2. Synthesis of methyl 2-fluoro-5-hydroxy-4-nitrobenzoate (3)

To a solution of 2-fluoro-5-hydroxy-4-nitrobenzoic acid (2.5 g, 12.43 mmol) in DCM (25 mL) were added (COCl) ₂ (3.16 g, 24.86 mmol, 2.18 mL) and DMF (95.00 mg, 1.30 mmol, 0.1 mL) at 0 °C, and the mixture was stirred at 0 °C for 0.5 h. Then, MeOH (25 mL) was slowly added, and the mixture was stirred at 20 °C for 1 h. TLC (Petroleum ether:EtOAc=10:1) confirmed the formation of a new spot. The mixture was concentrated under reduced pressure to obtain the title compound (2.96 g, crude) as a yellow solid.

Step 3. Synthesis of methyl 5-(2-((tert-butyldimethylsilyl)oxy)ethoxy)-2-fluoro-4-nitrobenzoate (4)

To a solution of methyl 2-fluoro-5-hydroxy-4-nitrobenzoate (1.5 g, 6.97 mmol) and (2-bromoethoxy)(tert-butyl)dimethylsilane (2.17 g, 9.06 mmol) in DMF (10 mL) was added K ₂ CO ₃ (1.93 g, 13.94 mmol), and the mixture was stirred at 100 °C for 14 h. The mixture was diluted with water (50 mL) and extracted with EtOAc (30 mL x 2). The combined organic layer was washed with brine (10 mL x 2), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (12 g SepaFlash® silica flash column, Eluent of 5% EtOAc/Commercial hexanes gradient @ 200 mL/min) to give the title compound (2.3 g, 6.16 mmol, 88.33% yield) as a yellow solid.

Step 4. Synthesis of methyl 4-amino-5-(2-((tert-butyldimethylsilyl)oxy)ethoxy)-2-fluorobenzoate (5)

Solution 1: (Methyl 5-(2-((tert-butyldimethylsilyl)oxy)ethoxy)-2-fluoro-4-nitrobenzoate (2.3 g, 6.16 mmol) in THF (23 mL) and MeOH (11.5 mL). The fixed bed (named FLR ₁ , volume 1 mL) was packed with a granular catalyst (Pt/C (1.37 g, 1% purity)). The H ₂ pressure regulator was adjusted to 1.5 Mpa, and the H ₂ flow rate (H ₂ , 10 sccm). The solution 1 was pumped by pump 1 (S ₁ , P1, 0.4 mL/min) and flowed into reactor 1 (FLR ₁ , SS, Fixed bed, 6.350 (1/4") mm, 1.0 mL, 50.0 °C). The reaction mixture was The mixture was continuously collected from the reactor into a storage container. The peak of the target mass was confirmed by LCMS. The mixture was concentrated under reduced pressure to obtain the title compound (2.2 g, crude) as a yellow solid. MS(M+H) ⁺ = 344.3

Step 5. Synthesis of methyl (R)-5-(2-((tert-butyldimethylsilyl)oxy)ethoxy)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-2-fluorobenzoate (7)

To a solution of methyl 4-amino-5-(2-((tert-butyldimethylsilyl)oxy)ethoxy)-2-fluorobenzoate (0.3 g, 873.45 μmol), (R)-2-chloro-8-cyclopentyl-5,7-dimethyl-7,8-dihydropteridin-6(5H)-one (0.2 g, 712.37 μmol) and K ₃ PO ₄ (453.64 mg, 2.14 mmol) in dioxane (8 mL) were added Pd ₂ (dba) ₃ (26.09 mg, 28.49 μmol) and Xantphos (24.73 mg, 42.74 μmol), and the mixture was stirred at 100 °C for 14 h under N ₂ . The peak of the target mass was identified by LCMS. The mixture was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (12 g SepaFlash® silica flash column, eluent of 30–50% EtOAc/Petroleum ether gradient @ 200 mL/min) to give the title compound (350 mg, 595.48 μmol, 83.59% yield) as a yellow oil. MS(M+H) ⁺ = 588.4

Step 6. Synthesis of (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-2-fluoro-5-(2-hydroxyethoxy)benzoic acid (8)

To a solution of methyl (R)-5-(2-((tert-butyldimethylsilyl)oxy)ethoxy)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-2-fluorobenzoate (350 mg, 595.48 μmol) in MeOH (3 mL) and THF (3 mL) was added NaOH (2 M, 3 mL), and the mixture was stirred at 20 °C for 14 h. The peak of the desired mass was identified by LCMS. The mixture was concentrated under reduced pressure. The product was diluted with 2 N HCl/dioxane (10 mL), and the mixture was concentrated under reduced pressure to give the title compound (0.3 g, crude) as a yellow solid. MS(M+H) ⁺ = 460.2

Step 7. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-2-fluoro-5-(2-hydroxyethoxy)benzamide (Compound 9)

The title compound (2.3 mg, 2.60 μmol, 1.99% yield, 95% purity) was obtained as a white solid by a similar method to step 3 of Example 3. MS(M+H) ⁺ = 840.7

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.72 (s, 1H), 8.37 (d, J = 13.9 Hz, 1H), 8.22 (s, 1H), 7.93 (s, 1H), 7.77 - 7.66 (m, 1H), 7.17 (d, J = 7.0 Hz, 1H), 6.88 (d, J = 8.4 Hz, 2H), 6.50 (d, J = 8.4 Hz, 2H), 5.56 (br t, J = 5.4 Hz, 1H), 5.21 (t, J = 5.8 Hz, 1H), 4.53 - 4.41 (m, 1H), 4.34 (q, J = 6.8 Hz, 1H), 4.13 - 4.04 (m, 2H), 3.80 - 3.72 (m, 2H), 3.70 - 3.60 (m, 2H), 3.24 (s, 3H), 2.89 - 2.76 (m, 4H), 2.63 - 2.56 (m, 1H), 2.47 - 2.40 (m, 1H), 2.30 - 2.21 (m, 1H), 2.14 (br t, J = 10.4 Hz, 2H), 2.09 - 1.96 (m, 3H), 1.94 - 1.85 (m, 2H), 1.84 - 1.67 (m, 7H), 1.66 - 1.55 (m, 2H), 1.52 - 1.42 (m, 1H), 1.32 (br t, J = 9.7 Hz, 4H), 1.26 - 1.21 (m, 5H), 1.19 - 1.09 (m, 2H)

Example 10. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-(2-hydroxyethoxy)benzamide (Compound 10)

Step 1. Synthesis of methyl 3-(2-hydroxyethoxy)-4-nitrobenzoate (2)

To a solution of methyl 3-hydroxy-4-nitrobenzoate (10.00 g, 50.72 mmol), ethane-1,2-diol (4.09 g, 65.94 mmol), and PPh ₃ (19.96 g, 76.09 mmol) in THF (200 mL) was added DIAD (15.39 g, 76.09 mmol) at 0 °C. The mixture was stirred at 20 °C for 16 h. TLC (EtOAc:PE = 1:1) confirmed the complete consumption of methyl 3-hydroxy-4-nitrobenzoate and the appearance of one new major spot with high polarity. The mixture was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (ISCO®; 200 g SepaFlash® silica flash column, Eluent of 30–40% EtOAc/Petroleum ether gradient @ 100 mL/min) to give the title compound (10 g, 24.88 mmol, 49.04% yield, 60% purity) as a yellow solid. MS(M+H) ⁺ = 242.2.

Step 2. Synthesis of methyl 3-(2-((tert-butyldimethylsilyl)oxy)ethoxy)-4-nitrobenzoate (3)

To a solution of methyl 3-(2-hydroxyethoxy)-4-nitrobenzoate (10.00 g, 24.88 mmol), DMAP (304 mg, 2.49 mmol), and TEA (5.03 g, 49.75 mmol) in DCM (100 mL) was added TBSCl (4.87 g, 32.34 mmol). The mixture was stirred at 20 °C for 14 h. TLC (PE:EtOAc = 1:1) confirmed the complete consumption of methyl 3-(2-hydroxyethoxy)-4-nitrobenzoate and the appearance of one new major spot with high polarity. The mixture was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (ISCO®; 120 g SepaFlash® silica flash column, Eluent of 0–10% EtOAc/Petroleum ether gradient @ 100 mL/min) to give the title compound (6.00 g, 15.19 mmol, 61.07% yield, 90% purity) as a pale yellow oil.

Step 3. Synthesis of methyl 4-amino-3-(2-hydroxyethoxy)benzoate & methyl 4-amino-3-(2-((tert-butyldimethylsilyl)oxy)ethoxy)benzoate (4 & 4A)

A solution of methyl 3-(2-((tert-butyldimethylsilyl)oxy)ethoxy)-4-nitrobenzoate (6.00 g, 15.19 mmol) in MeOH (100 mL) and THF (60 mL) was dissolved to obtain a clear solution. The fixed bed (volume 15 mL) was packed with a granular catalyst of 1% Pt/Al ₂ O ₃ and heated to 50 °C. The H ₂ pressure controller was adjusted to 1.5 MPa. The solution was injected into the fixed bed (3 mL, 50 °C) (flow rate 0.9 mL/min), and the H ₂ flow rate was adjusted to 60 mL/min. The reaction mixture was passed through the reactor for 3.3 min and then collected. The eluate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (ISCO®; 40 g SepaFlash® silica flash column, Eluent of 0–20% then 80–90% EtOAc/Petroleum ether gradient @ 60 mL/min) to afford methyl 4-amino-3-(2-((tert-butyldimethylsilyl)oxy)ethoxy)benzoate (2.60 g, 7.91 mmol, 99% purity) as a pale yellow oil and methyl 4-amino-3-(2-hydroxyethoxy)benzoate (1.30 g, 6.09 mmol, 99% purity) as a white solid. MS(M+H) ⁺ = 326.2 & 212.1.

Step 4. Synthesis of methyl (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-(2-hydroxyethoxy)benzoate (6)

A mixture of methyl 4-amino-3-(2-hydroxyethoxy)benzoate (100 mg, 468.72 μmol), (R)-2-chloro-8-cyclopentyl-7-ethyl-5-methyl-7,8-dihydropteridin-6(5H)-one (180 mg, 609.33 μmol), Xantphos (54 mg, 93.74 μmol), Pd ₂ (dba) ₃ (42.9 mg, 46.87 μmol), and K ₃ PO ₄ (298 mg, 1.41 mmol) in dioxane (5 mL) was degassed and purged three times with N ₂ , and the mixture was stirred at 100 °C under CN ₂ for 16 h. The desired mass peak (44%) was identified by LCMS. The mixture was concentrated under reduced pressure, and the residue was purified by flash silica gel chromatography (ISCO®; 12 g SepaFlash® silica flash column, Eluent of 5–8% MeOH/EtOAc @ 40 mL/min) to give the title compound (110 mg, 220.22 μmol, 46.98% yield, 94% purity) as a pale yellow oil. MS(M+H) ⁺ = 470.4.

Step 5. Synthesis of (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-(2-hydroxyethoxy)benzoic acid (7)

To a solution of methyl (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-(2-hydroxyethoxy)benzoate ( ₁₁₀ mg, 220.22 μmol) in MeOH (2 mL), THF (1 mL), and H 2 O (1 mL) was added LiOH (16 mg, 660.66 μmol). The mixture was stirred at 20 °C for 16 h. The desired mass peak (95%) was identified by LCMS. The mixture was concentrated under reduced pressure, the suspension was diluted with H ₂ O (5 mL), adjusted to pH = 2 with HCl (1 M), filtered, and the filter cake was washed with H ₂ O (10 mL) and dried in vacuo to obtain the title compound (90 mg, 187.70 μmol, 85.23% yield, 95% purity) as a pale yellow solid. MS (M + H) + = 456.2.

Step 6. Synthesis of benzyl ((1r,4r)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)carbamate (10)

To a solution of 3-(4-aminophenyl)piperidine-2,6-dione (300 mg, 1.47 mmol) and benzyl ((1r,4r)-4-(4-formylpiperidin-1-yl)cyclohexyl)carbamate (455 mg, 1.32 mmol) in DCM (10 mL) and DMF (2 mL) was added AcOH (88 mg, 1.47 mmol), and the mixture was stirred at 20 °C for 1 h, after which NaBH(OAc) ₃ (778 mg, 3.67 mmol) was added. The mixture was stirred at 20 °C for an additional 14 h. The desired mass peak (94%) was identified by LCMS. The reaction mixture was diluted with water (20 mL), adjusted to pH = 9 with saturated NaHCO ₃ , and extracted with DCM (30 mL Х 3 ). The mixed organic layer was washed with brine (20 mL X 2), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (ISCO®; 12 g SepaFlash® silica flash column, eluent of 20–30% MeOH/EtOAc @ 40 mL/min) to give the title compound (380 mg, 706.25 μmol, 48.08% yield, 99% purity) as a white solid. MS(M+H) ⁺ = 533.4.

Step 7. Synthesis of 3-(4-(((1-((1r,4r)-4-aminocyclohexyl)piperidin-4-yl)methyl)amino)phenyl)piperidine-2,6-dione (11)

A mixture of benzyl ((1r,4r)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)carbamate (120 mg, 223.03 μmol) in TFA (3 mL) was degassed and purged three times under N ₂ , and the mixture was stirred at 30 °C under CN ₂ for 14 h. The desired mass peak was identified by LCMS. The mixture was concentrated under reduced pressure to give the title compound (114 mg, 222.41 μmol, 99.72% yield, TFA) as a brown oil. MS(M+H) ⁺ = 399.2.

Step 8. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-(2-hydroxyethoxy)benzamide (Compound 10)

To a solution of (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-(2-hydroxyethoxy)benzoic acid (90 mg, 187.70 μmol) in DMF (1.5 mL) were added HATU (78 mg, 204.62 μmol) and DIPEA (144 mg, 1.11 mmol). The mixture was stirred at 20 °C for 1 h. 3-(4-(((1-((1r,4r)-4-aminocyclohexyl)piperidin-4-yl)methyl)amino)phenyl)piperidine-2,6-dione (114 mg, 222.41 μmol, TFA salt) was added, and the mixture was stirred at 20 °C for 1 h. The desired mass peak (92%) was identified by LCMS. The mixture was filtered, and the filtrate was purified by Prep-HPLC (column: Waters Xbridge 150 Х 25 mm Х 10 μm; mobile phase: [water (NH ₄ HCO ₃ ) - ACN]; gradient: 32% - 62% B over 10 min), and the eluate was lyophilized to obtain the title compound (70.71 mg, 83.06 μmol, 37.34% yield, 98.2% purity) as a white solid. MS(M+H) ⁺ = 836.5.

¹ H NMR (400 MHz, DMSO- d ₆ ) δ = 10.72 (s, 1H), 8.41 (d, J = 8.8 Hz, 1H), 8.03 - 7.97 (m, 2H), 7.84 (s, 1H), 7.50 - 7.42 (m, 2H), 6.88 (d, J = 8.4 Hz, 2H), 6.50 (d, J = 8.4 Hz, 2H), 5.61 - 5.52 (m, 1H), 5.14 (t, J = 6.0 Hz, 1H), 4.40 - 4.30 (m, 1H), 4.28 - 4.21 (m, 1H), 4.15 - 4.07 (m, 2H), 3.82 - 3.75 (m, 2H), 3.74 - 3.66 (m, 1H), 3.66 - 3.59 (m, 1H), 3.25 (s, 3H), 2.92 - 2.79 (m, 4H), 2.65 - 2.55 (m, 1H), 2.46 - 2.40 (m, 1H), 2.30 - 2.23 (m, 1H), 2.21 - 2.11 (m, 2H), 2.10 - 1.96 (m, 3H), 1.94 - 1.85 (m, 4H), 1.85 - 1.71 (m, 8H), 1.68 - 1.57 (m, 3H), 1.55 - 1.45 (m, 1H), 1.41 - 1.28 (m, 4H), 1.21 - 1.08 (m, 2H), 0.77 (t, J = 7.6 Hz, 3H).

Example 11. Synthesis of N-((1r,4R)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-4-(((R)-8-ethyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzamide (Compound 11)

Step 1. Synthesis of methyl benzyl-D-alaninate (2)

To a solution of methyl D-alaninate (20 g, 143.29 mmol, HCl salt) and bromomethylbenzene (22.06 g, 128.96 mmol, 15.32 mL) in DMF (200 mL) was added K ₂ CO ₃ (39.61 g, 286.57 mmol), and the resulting mixture was stirred at 20 °C for 14 h. The peak of the target mass (19%) was identified by LCMS. The mixture was filtered, and the filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (200 g SepaFlash® silica flash column, Eluent of 0–20% EtOAc/Petroleum ether gradient @ 200 mL/min) to give the title compound (15 g, 77.62 mmol, 54.17% yield) as a yellow oil. MS (M+H) ⁺ =194.1

Step 2. Synthesis of methyl N-benzyl-N-ethyl-D-alaninate (3)

To a solution of methyl benzyl-D-alaninate (8 g, 41.40 mmol) and acetaldehyde (6.84 g, 62.10 mmol, 8.71 mL) in DCM (80 mL) were added MgSO ₄ (14.95 g, 124.20 mmol) and TEA (12.57 g, 124.20 mmol, 17.29 mL), and the resulting mixture was stirred at 20 °C for 1 h. NaBH(OAc) ₃ (13.16 g, 62.10 mmol) was added, and the resulting mixture was stirred at 20 °C for 14 h. The main peak of the target mass was confirmed by LCMS. The mixture was quenched with NaHCO ₃ solution (100 mL) at 0 °C, extracted with DCM (50 mL x 3), and the combined organic layer was washed with NaHCO ₃ solution (100 mL), dried over Na ₂ SO _{4 ,} and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (80 g SepaFlash® silica flash column, Eluent of 0–20% EtOAc/Petroleum ether gradient @ 100 mL/min) to give the title compound (6 g, 27.11 mmol, 65.49% yield) as a colorless oil. MS (M+H) ⁺ = 222.3

Step 3. Synthesis of methyl ethyl-D-alaninate (4)

To a solution of methyl N-benzyl-N-ethyl-D-alaninate (6 g, 27.11 mmol) in MeOH (200 mL) were added HCl (12 M, 4.52 mL) and Pd/C (2 g, 1.88 mmol, 10% purity) under N ₂ , and the mixture was stirred at 20-25 °C under CH ₂ (45 Psi) for 14 h. Complete consumption of the starting material was confirmed by LCMS. The mixture was filtered, and the filtrate was concentrated under reduced pressure to give the title compound (5.1 g, crude, HCl salt) as a brown solid.

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 9.73 (s, 1H), 9.30 (s, 1H), 4.17 - 4.08 (m, 1H), 3.76 (s, 3H), 3.03 - 2.92 (m, 2H), 1.47 (d, J = 7.2 Hz, 3H), 1.23 (t, J = 7.3 Hz, 3H).

Step 4. Synthesis of methyl N-(2-chloro-5-nitropyrimidin-4-yl)-N-ethyl-D-alaninate (6)

To a solution of methyl ethyl-D-alaninate (5.1 g, 30.42 mmol, HCl salt) and 2,4-dichloro-5-nitro-pyrimidine (5.90 g, 30.42 mmol) in acetone (100 mL) was added K ₂ CO ₃ (12.61 g, 91.27 mmol), and the resulting mixture was stirred at 20 °C for 14 h. The major peak of the desired mass was identified by LCMS. The mixture was filtered and concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (40 g SepaFlash® silica flash column, Eluent of 0–20% EtOAc/Petroleum ether gradient @ 100 mL/min) to give the title compound (6.9 g, 23.90 mmol, 78.56% yield) as a yellow oil. MS (M+H) ⁺ =289.1

Step 5. Synthesis of (R)-2-chloro-8-ethyl-7-methyl-7,8-dihydropteridin-6(5H)-one (7)

To a solution of methyl N-(2-chloro-5-nitropyrimidin-4-yl)-N-ethyl-D-alaninate (6.9 g, 23.90 mmol) in AcOH (70 mL) was added Fe (4.00 g, 71.70 mmol), and the resulting mixture was stirred at 60 °C for 1 h. The major peak of the desired mass was identified by LCMS. The mixture was concentrated under reduced pressure. The residue was diluted with EtOAc (50 mL) and water (50 mL), and the mixture was adjusted to pH=8 with saturated aqueous Na ₂ CO ₃ solution. The mixture was filtered, and the filter cake was washed with EtOAc (50 mL). The filtrate was extracted with EtOAc (10 mL x 3), and the combined organic layers were washed with water (50 mL), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure. The product was triturated with MTBE (50 mL), filtered, and the filter cake was collected to obtain (R)-2-chloro-8-ethyl-7-methyl-7,8-dihydropteridin-6(5H)-one (0.8 g, 3.39 mmol, 14.18% yield, 96% purity) as a yellow solid. The filtrate was concentrated under reduced pressure to obtain the title compound (3.8 g, 16.77 mmol, 70.14% yield) as a yellow oil. MS (M+H) ⁺ = 227.2

Step 6. Synthesis of (R)-2-chloro-8-ethyl-5,7-dimethyl-7,8-dihydropteridin-6(5H)-one (8)

_To a solution of (R)-2-chloro-8-ethyl-7-methyl-7,8-dihydropteridin-6(5H)-one (0.8 g, 3.53 mmol) and _K2CO3 (1 g, 7.24 mmol) in DMF (20 mL) was added MeI (751 mg, 5.29 mmol, 329.39 μL), and the mixture was stirred at 25 °C for 14 h. The major peak of the desired mass was identified by LCMS. The mixture was diluted with water (100 mL), extracted with EtOAc (50 mL x 3), and the combined organic layers were washed with brine (100 mL), _dried over _Na2SO4 , and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (10 g SepaFlash® silica flash column, eluent of 0–50% EtOAc/Commercial hexanes gradient @ 100 mL/min) to give the title compound as a yellow solid. MS (M+H) ⁺ = 241.2

Step 7. Synthesis of ((R)-4-((8-ethyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoic acid (10)

To a solution of ( _R )-2-chloro-8-ethyl-5,7-dimethyl-7,8-dihydropteridin-6(5H)-one (300 mg, 1.25 mmol) and 4-amino-3-methoxy-benzoic acid (320 mg, 1.91 mmol) in EtOH (1 mL) and H 2 O (5 mL) was added HCl (12 M, 0.4 mL), and the mixture was stirred at 100 °C for 14 h. The main peak of the desired mass was identified by LCMS. The mixture was filtered, and the filter cake was dried to obtain the title compound (0.3 g, 807.78 μmol, 64.81% yield) as a white solid. MS (M+H) ⁺ = 372.2

Step 8. Synthesis of N-((1r,4R)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-4-(((R)-8-ethyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzamide (Compound 11)

To a solution of ((R)-4-((8-ethyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoic acid (40 mg, 107.70 μmol) in DMF (3 mL) were added HATU (49.14 mg, 129.24 μmol) and DIPEA (41.76 mg, 323.11 μmol, 56.28 μL), and the mixture was stirred at 20 °C for 0.5 h, 3-(4-(((1-((1r,4r)-4-aminocyclohexyl)piperidin-4-yl)methyl)amino)phenyl)piperidine-2,6-dione (55.20 mg, 107.70 μmol, TFA salt) was added, and the mixture was stirred at 20 °C for 1 h. It was stirred. The main peak of the target mass was confirmed by LCMS. The mixture was diluted with H ₂ O (20 mL) and extracted with EtOAc (10 mL x 3), and the combined organic layer was washed with brine (20 mL), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by prep-HPLC (column: Phenomenex Luna C18 150 * 25 mm * 10 um; mobile phase: [H ₂ O (0.1% TFA)-ACN]; gradient: 0%-28% B over 15.0 min) and the eluate was lyophilized. The target product was dissolved in H ₂ O (20 mL), adjusted to pH = 8~9 with NaHCO ₃ solid, and the resulting suspension was extracted with EtOAc (10 mL x 3), and the combined organic layer was dried over Na ₂ SO ₄ and filtered. The filtrate was concentrated under reduced pressure, and the residue The title compound was obtained as a white solid (27.2 mg, 35.45 μmol, 32.92% yield, 98% purity) by lyophilization. MS(M+H) ⁺ =752.4

^1H NMR (400 MHz, DMSO _- d6 ) δ = 10.73 (s, 1H), 8.46 (d, J = 8.5 Hz, 1H), 8.07 - 7.99 (m, 1H), 7.83 (s, 1H), 7.60 (s, 1H), 7.53 - 7.43 (m, 2H), 6.89 (d, J = 8.5 Hz, 2H), 6.51 (d, J = 8.4 Hz, 2H), 5.57 (t, J = 5.3 Hz, 1H), 4.34 (q, J = 7.0 Hz, 1H), 3.99 - 3.82 (m, 4H), 3.78 - 3.67 (m, 1H), 3.63 (dd, J = 4.9, 10.6 Hz, 1H), 3.29 - 3.26 (m, 1H), 3.23 (s, 3H), 2.88 - 2.82 (m, 3H), 2.66 - 2.57 (m, 1H), 2.47 - 2.39 (m, 2H), 2.30 - 2.25 (m, 1H), 2.19 - 2.11 (m, 2H), 2.11 - 2.05 (m, 1H), 2.09 - 2.00 (m, 1H), 1.92 - 1.86 (m, 2H), 1.82 - 1.71 (m, 4H), 1.52 - 1.46 (m, 1H), 1.37 - 1.30 (m, 6H), 1.29 - 1.21 (m, 4H), 1.17 - 1.08 (m, 2H).

Example 12. Synthesis of 4-(((R)-7,8-diethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 12)

Step 1. Synthesis of methyl (R)-2-(benzyl(ethyl)amino)butanoate (3)

To a solution of methyl (R)-2-aminobutanoate HCl (10 g, 65.10 mmol, HCl salt) in ACN (400 mL) were added DIPEA (16.84 g, 130.33 mmol, 22.7 mL) and BnBr (10.00 g, 58.47 mmol, 6.94 mL), and the mixture was stirred at 60 °C for 4 h. TLC (Petroleum ether: EtOAc=1:10) confirmed the consumption of BnBr and the appearance of a new spot. TEA (19.76 g, 195.30 mmol, 27.18 mL) and acetaldehyde (21.59 g, 196.02 mmol, 27.50 mL) were then added, and the mixture was stirred at 25 °C for 30 min. After NaBH(OAc) ₃ (41.39 g, 195.30 mmol) was added at 0 °C, the mixture was stirred at 25 °C for 14 h. LCMS confirmed that methyl (R)-2-(benzylamino)butanoate remained. Additionally, acetaldehyde (21.51 g, 195.30 mmol, 27.40 mL) was added, and the mixture was stirred at 25 °C for 30 min. After NaBH(OAc) ₃ (41.39 g, 195.30 mmol) was added, the mixture was stirred at 25 °C for 14 h. LCMS confirmed that methyl (R)-2-(benzylamino)butanoate was consumed and a peak of the desired mass was obtained. The mixture was diluted with saturated NaHCO ₃ (200 mL) at 0 °C and extracted with EtOAc (100 mL x 3). The combined organic layers were washed with saturated NaHCO ₃ (100 mL), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (120 g SepaFlash® silica flash column, Eluent of 50–100% EtOAc/Petroleum ether gradient @ 100 mL/min) to give the title compound (10.6 g, 45.04 mmol, 69.19% yield) as a yellow oil. MS(M+H) ⁺ = 236.5.

Step 2. Synthesis of methyl (R)-2-(ethylamino)butanoate (4)

A solution of Pd/C (1 g, 10% purity) in EtOH (30 mL) was slowly added to a solution of methyl (R)-2-(benzyl(ethyl)amino)butanoate (5 g, 21.25 mmol) and HCl (12 M, 3.54 mL) in EtOH (30 mL) under N ₂ , and the mixture was stirred at 25 °C under CH ₂ (45 Psi) for 14 h. TLC (Petroleum ether: EtOAc=5:1) confirmed consumption of the starting material. The mixture was filtered, and the filter cake was washed with EtOH (500 mL). The filtrate was concentrated under reduced pressure to give the title compound (3.9 g, crude, HCl salt) as a white solid.

Step 3. Synthesis of methyl (R)-2-((2-chloro-5-nitropyrimidin-4-yl)(ethyl)amino)butanoate (6)

To a solution of methyl (R)-2-(ethylamino)butanoate (3.9 g, 21.47 mmol, HCl salt) and 2,4-dichloro-5-nitropyrimidine (4.16 g, 21.47 mmol) in acetone (80 mL) was added K ₂ CO ₃ (8.90 g, 64.41 mmol), and the mixture was stirred at 25 °C for 14 h. The desired mass peak (58%) was identified by LCMS. The mixture was diluted with water (100 mL) and extracted with EtOAc (50 mL x 3). The combined organic layer was washed with water (50 mL), dried over Na ₂ SO _{4 ,} and filtered. The filtrate was concentrated under reduced pressure and purified by flash silica gel chromatography (20 g SepaFlash® silica flash column, Eluent of 20% EtOAc/Petroleum ether gradient @ 200 mL/min) to give the title compound (3.14 g, 9.65 mmol, 44.93% yield, 93% purity) as a yellow oil. MS(M+H) ⁺ = 303.2.

Step 4. Synthesis of (R)-2-chloro-7,8-diethyl-7,8-dihydropteridin-6(5H)-one (7)

To a solution of methyl (R)-2-((2-chloro-5-nitropyrimidin-4-yl)(ethyl)amino)butanoate (3.14 g, 10.37 mmol) in AcOH (30 mL) was added Fe (2.32 g, 41.49 mmol), and the mixture was stirred at 60 °C for 2 h. LCMS showed that the starting material was consumed. The mixture was concentrated under reduced pressure. The product was diluted with EtOAc (50 mL) and water (50 mL), and the mixture was adjusted to about pH 8 with saturated Na ₂ CO ₃ . The mixture was filtered, and the filter cake was washed with EtOAc (50 mL). The filtrate was extracted with EtOAc (10 mL x 3), and the combined organic layers were washed with water (50 mL), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure and purified by flash silica gel chromatography (12 g SepaFlash® silica flash column, Eluent of 50–100% EtOAc/Petroleum ether gradient @ 100 mL/min) to give the title compound (1.03 g, 3.85 mmol, 37.13% yield, 90% purity) as a yellow solid. MS(M+H) ⁺ =241.4.

Step 5. Synthesis of (R)-2-chloro-7,8-diethyl-5-methyl-7,8-dihydropteridin-6(5H)-one (8)

To a solution of (R)-2-chloro-7,8 _- diethyl-7,8-dihydropteridin-6(5H)-one (1.03 g, 4.28 mmol) and _K2CO3 (1.18 g, 8.56 mmol) in DMF (10 mL) was added MeI (912.00 mg, 6.43 mmol, 0.4 mL), and the mixture was stirred at 25 °C for 14 h. The desired mass peak (61%) was identified by LCMS. The mixture was diluted with water (30 mL), extracted with EtOAc (30 mL x 3), and the combined organic layers were washed with brine (50 mL), _dried over _Na2SO4 , and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (5 g SepaFlash® silica flash column, Eluent of 10% EtOAc/Petroleum ether gradient @ 50 mL/min) to give the title compound (810 mg, 2.93 mmol, 68.37% yield, 92% purity) as a yellow solid. MS(M+H) ⁺ = 255.2.

SFC Method Com: Column: Chiralpak AD-3 50Х4.6 mm ID, 3um; Mobile phase: Phase A for CO ₂ , and Phase B for EtOH (0.05%DEA); Gradient elution: B in A from 5% to 40%; Flow rate: 3mL/min; Detector: DAD; Column Temp: 35C; Back Pressure: 100Bar.

Step 6. Synthesis of (R)-4-((7,8-diethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoic acid (10)

To a solution of (R)-2-chloro-7,8-diethyl-5-methyl-7,8-dihydropteridin-6(5H)-one (810 mg, 3.18 mmol) and 4 _- amino-3-methoxybenzoic acid (798 mg, 4.77 mmol) in EtOH (3 mL) and H 2 O (12 mL) was added HCl (12 M, 0.8 mL), and the mixture was stirred at 100 °C for 12 h. The desired mass peak (78%) was identified by LCMS. The mixture was concentrated under reduced pressure. The product was diluted with water (20 mL), filtered, and the filter cake was washed with water (10 mL). The filter cake was collected and concentrated under reduced pressure to give the title compound (910 mg, 2.31 mmol, 72.76% yield, 98% purity) as a yellow solid. MS(M+H) ⁺ =386.2.

Step 7. Synthesis of benzyl ((1r,4r)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)carbamate (11C)

To a solution of 3-(4-aminophenyl)piperidine-2,6-dione (310 mg, 1.52 mmol) and benzyl ((1r,4r)-4-(4-formylpiperidin-1-yl)cyclohexyl)carbamate (500 mg, 1.45 mmol) in DCM (20 mL) was added AcOH (83.92 mg, 1.40 mmol, 80 μL), and the mixture was stirred at 25 °C for 30 min. NaBH(OAc) ₃ (620.00 mg, 2.93 mmol) was added at 0 °C, and the mixture was stirred at 25 °C for 1 h. The desired mass peak (94%) was confirmed by LCMS. The mixture was diluted with EtOAc (10 mL) and saturated NaHCO ₃ solution (10 mL), extracted with EtOAc (10 mL x 3), and the combined organic layers were concentrated under reduced pressure. The product was diluted with MTBE (20 mL), and the mixture was stirred at 25 °C for 15 minutes. The mixture was filtered, and the filter cake was washed with MTBE (10 mL). The filter cake was collected and concentrated under reduced pressure to give the title compound (640 mg, 1.20 mmol, 82.77% yield, 100% purity) as a yellow solid. MS(M+H) ⁺ = 533.3.

Step 8. Synthesis of 3-(4-(((1-((1r,4r)-4-aminocyclohexyl)piperidin-4-yl)methyl)amino)phenyl)piperidine-2,6-dione (11)

A solution of benzyl ((1r,4r)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)carbamate (0.5 g, 938.66 μmol) in TFA (15.35 g, 134.62 mmol, 10 mL) was stirred at 60 °C for 3 h. The desired mass peak (75%) was identified by LCMS. The mixture was concentrated under reduced pressure to give the title compound (480 mg, crude, TFA salt) as a yellow oil. MS(M+H) ⁺ = 399.3.

Step 9. Synthesis of 4-(((R)-7,8-diethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 12)

To a solution of (R)-4-((7,8-diethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoic acid (0.36 g, 934.06 μmol) and HATU (426.19 mg, 1.12 mmol) in DMF (8 mL) was added DIPEA (1.21 g, 9.34 mmol, 1.63 mL), and the mixture was stirred at 25 °C for 15 min. Afterwards, a solution of 3-(4-(((1-((1r,4r)-4-aminocyclohexyl)piperidin-4-yl)methyl)amino)phenyl)piperidine-2,6-dione (480 mg, 936.47 μmol, TFA salt) in DMF (10 mL) was added at 0 °C, and the mixture was stirred at 25 °C for 14 h. The desired mass peak (75%) was identified by LCMS. The mixture was diluted with water (20 mL) and saturated NaHCO ₃ (20 mL), and extracted with EtOAc (10 mL x 3). The combined organic layer was washed with water (10 mL), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure. The product was purified by prep-HPLC (column: Phenomenex luna C18 150*25 mm* 10um; mobile phase: [water (TFA) -ACN]; gradient: 13%-43% B over 10 min), and the eluate was lyophilized to obtain the title compound as a white solid (503 mg, 485.80 μmol, 52.01% yield, 96% purity, 2TFA salt). MS(M+H) ⁺ =766.5.

SFC Method details: "Column: Chiralpak AD-3 50Х4.6mm ID, 3um Mobile phase: Phase A for CO ₂ , and Phase B for IPA+ACN (0.05%DEA); Gradient elution: 60% IPA+ACN (0.05% DEA) in CO ₂ Flow rate: 3mL/min; Detector: PDA Column Temp: 35C; Back Pressure: 100Bar"

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.73 (s, 1H), 9.36 - 8.93 (m, 2H), 8.27 (br d, J = 7.0 Hz, 1H), 8.19 - 8.07 (m, 1H), 7.80 (s, 1H), 7.54 (br s, 2H), 6.91 (br d, J = 8.3 Hz, 2H), 6.55 (br d, J = 7.9 Hz, 2H), 4.58 - 4.52 (m, 1H), 3.94 (s, 3H), 3.92 - 3.86 (m, 1H), 3.82 - 3.74 (m, 1H), 3.64 (br dd, J = 4.9, 10.8 Hz, 1H), 3.52 - 3.38 (m, 3H), 3.22 (s, 3H), 3.19 - 3.08 (m, 1H), 3.04 - 2.90 (m, 4H), 2.68 - 2.56 (m, 1H), 2.47 - 2.39 (m, 1H), 2.11 - 1.76 (m, 11H), 1.70 - 1.53 (m, 2H), 1.42 (q, J = 11.8 Hz, 4H), 1.24 (t, J = 7.0 Hz, 3H), 0.74 (t, J = 7.4 Hz, 3H).

Example 13. Synthesis of 4-(((R)-7,8-diethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-(2-hydroxyethoxy)benzamide (Compound 13)

Step 1. Synthesis of methyl (R)-3-(2-((tert-butyldimethylsilyl)oxy)ethoxy)-4-((7,8-diethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)benzoate (3)

The title compound (800 mg, 1.43 mmol, 93.84% yield, 97% purity) was obtained as a yellow solid by a similar method to step 4 of Example 10. MS(M+H) ⁺ =544.2.

Step 2. Synthesis of methyl (R)-4-((7,8-diethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-(2-hydroxyethoxy)benzoate (4)

To a solution of methyl (R)-3-(2-((tert-butyldimethylsilyl)oxy)ethoxy)-4-((7,8-diethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)benzoate (500 mg, 891.99 μmol) in THF (8 mL) was added TBAF (1 M, 1.8 mL). The mixture was stirred at 20 °C for 14 h. The desired mass peak (100%) was confirmed by LCMS. The mixture was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (ISCO®; 12 g SepaFlash® silica flash column, eluent of 5–7% MeOH/EtOAc @ 40 mL/min) to give the title compound (330 mg, 768.39 μmol, 86.14% yield) as a pale yellow oil. MS(M+H) ⁺ = 430.1.

Step 3. Synthesis of (R)-4-((7,8-diethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-(2-hydroxyethoxy)benzoic acid (5)

To a solution of methyl (R)-4-((7,8-diethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-(2-hydroxyethoxy)benzoate (330 mg, 768.39 μmol) in MeOH (3 mL) and THF (3 mL) was added NaOH (2 M, 3 mL). The mixture was stirred at 20 °C for 16 h. The desired mass peak (100%) was confirmed by LCMS. The mixture was concentrated under reduced pressure and diluted with H ₂ O (5 mL). The mixture was adjusted to pH = 2 with HCl (1 M). The suspension was filtered. The filter cake was washed with _H2O (10 mL) and dried in vacuo to obtain the title compound (270 mg, 649.91 μmol, 84.58% yield) as a pale yellow solid. MS(M+H) ⁺ =416.1.

Step 4. Synthesis of 4-(((R)-7,8-diethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-(2-hydroxyethoxy)benzamide (Compound 13)

The title compound (91.54 mg, 112.13 μmol, 40.47% yield, 97.5% purity) was obtained as a yellowish-white solid by a similar method to step 8 of Example 10. MS(M+H) ⁺ =796.5.

¹ H NMR (400 MHz, DMSO- d ₆ ) δ = 10.72 (s, 1H), 8.46 (d, J = 8.4 Hz, 1H), 8.07 - 7.95 (m, 2H), 7.78 (s, 1H), 7.50 - 7.42 (m, 2H), 6.88 (d, J = 8.4 Hz, 2H), 6.50 (d, J = 8.8 Hz, 2H), 5.60 - 5.53 (m, 1H), 5.20 (t, J = 6.0 Hz, 1H), 4.38 - 4.31 (m, 1H), 4.17 - 4.06 (m, 2H), 4.04 - 3.92 (m, 1H), 3.83 - 3.75 (m, 2H), 3.75 - 3.66 (m, 1H), 3.66 - 3.59 (m, 1H), 3.25 (s, 3H), 2.93 - 2.77 (m, 4H), 2.65 - 2.55 (m, 2H), 2.47 - 2.44 (m, 1H), 2.30 - 2.24 (m, 1H), 2.19 - 2.10 (m, 2H), 2.10 - 1.96 (m, 2H), 1.91 - 1.70 (m, 8H), 1.53 - 1.46 (m, 1H), 1.41 - 1.29 (m, 4H), 1.23 (t, J = 7.2 Hz, 3H), 1.19 - 1.08 (m, 2H), 0.74 (t, J = 7.2 Hz, 3H).

Example 14. Synthesis of N-((1r,4R)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-methoxy-4-(((R)-5,7,8-trimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)benzamide (Compound 14)

Step 1. Synthesis of (R)-3-methoxy-4-((5,7,8-trimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)benzoic acid (3)

To a solution of ( _R )-2-chloro-5,7,8-trimethyl-7,8-dihydropteridin-6(5H)-one (100 mg, 441.18 μmol) and 4-amino-3-methoxy-benzoic acid (113.27 mg, 677.59 μmol) in EtOH (0.5 mL) and H 2 O (2.5 mL) was added HCl (12 M, 150 μL), and the mixture was stirred at 100 °C for 14 h. The main peak of the desired mass was identified by LCMS. The mixture was filtered, and the filter cake was dried to obtain the title compound (0.1 g, 279.83 μmol, 63.43% yield) as a white solid. MS (M+H) ⁺ = 358.2

Step 2. Synthesis of N-((1r,4R)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-methoxy-4-(((R)-5,7,8-trimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)benzamide (Compound 14)

The title compound (28.1 mg, 37.70 μmol, 33.68% yield, 99% purity) was obtained as a white solid by a similar method to step 2 of Example 1. MS(M+H) ⁺ = 738.5

^1H NMR (400 MHz, DMSO _- d6 ) δ = 10.76 (s, 1H), 8.49 (d, J = 8.4 Hz, 1H), 8.05 (d, J = 7.8 Hz, 1H), 7.84 (s, 1H), 7.61 (s, 1H), 7.52 - 7.48 (m, 1H), 7.46 (d, J = 1.6 Hz, 1H), 6.89 (d, J = 8.5 Hz, 2H), 6.51 (d, J = 8.5 Hz, 2H), 5.60 (t, J = 5.7 Hz, 1H), 4.30 (q, J = 6.8 Hz, 1H), 3.94 (s, 3H), 3.77 - 3.68 (m, 1H), 3.63 (dd, J = 5.0, 10.5 Hz, 1H), 3.24 (s, 3H), 3.07 (s, 3H), 2.94 - 2.80 (m, 4H), 2.64 - 2.58 (m, 1H), 2.48 - 2.41 (m, 1H), 2.35 - 2.27 (m, 1H), 2.28 - 2.23 (m, 2H), 2.09 - 1.95 (m, 2H), 1.93 - 1.87 (m, 2H), 1.84 - 1.70 (m, 4H), 1.54 - 1.46 (m, 1H), 1.41 - 1.36 (m, 4H), 1.30 (d, J = 6.9 Hz, 3H), 1.22 - 1.10 (m, 2H).

Example 15. Synthesis of N-((1r,4R)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-(2-hydroxyethoxy)-4-(((R)-5,7,8-trimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)benzamide (Compound 15)

Step 1. Synthesis of methyl N-(2-chloro-5-nitropyrimidin-4-yl)-N-methyl-D-alaninate (3)

To a solution of methyl methyl-D-alaninate (2 g, 13.02 mmol, HCl) and 2,4-dichloro-5-nitro-pyrimidine (2.53 g, 13.02 mmol) in acetone (30 mL) was added K ₂ CO ₃ (5.40 g, 39.06 mmol), and the resulting mixture was stirred at 20 °C for 14 h. The peak of the desired mass (41%) was identified by LCMS. The mixture was filtered and concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (40 g SepaFlash® silica flash column, Eluent of 0–20% EtOAc/Petroleum ether gradient @ 100 mL/min) to give the title compound (2 g, 7.28 mmol, 55.93% yield) as a yellow oil. MS (M+H) ⁺ = 275.2

Step 2. Synthesis of (R)-2-chloro-7,8-dimethyl-7,8-dihydropteridin-6(5H)-one (4)

To a solution of methyl N-(2-chloro-5-nitropyrimidin-4-yl)-N-methyl-D-alaninate (2 g, 7.28 mmol) in AcOH (20 mL) was added Fe (1.22 g, 21.85 mmol), and the resulting mixture was stirred at 60 °C for 1 h. The main peak of the desired mass was identified by LCMS. The mixture was concentrated under reduced pressure. The residue was diluted with EtOAc (50 mL) and water (50 mL), and the pH of the mixture was adjusted to 8 with saturated aqueous Na ₂ CO ₃ solution. The mixture was filtered, and the filter cake was washed with EtOAc (50 mL). The filtrate was extracted with EtOAc (50 mL x 3), and the combined organic layer was washed with water (50 mL), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure. The product was triturated with MTBE (50 mL), filtered, and the filter cake was collected to obtain the title compound (1.3 g, 6.11 mmol, 83.96% yield) as a yellow solid. MS (M+H) ⁺ = 212.9

Step 3. Synthesis of (R)-2-chloro-5,7,8-trimethyl-7,8-dihydropteridin-6(5H)-one (5)

_To a solution of (R)-2-chloro-7,8-dimethyl-7,8-dihydropteridin-6(5H)-one (800 mg, 3.76 mmol) and _K2CO3 (1.07 g, 7.71 mmol) in DMF (10 mL) was added MeI (800.54 mg, 5.64 mmol, 351.11 μL), and the mixture was stirred at 25 °C for 14 h. The peak of the target mass (90%) was identified by LCMS. The mixture was diluted with water (100 mL), extracted with EtOAc (50 mL x 3), and the combined organic layers were washed with brine (100 mL), dried over _{Na2SO4 ,} filtered, and the filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (10 g SepaFlash® silica flash column, eluent of 0–50% EtOAc/Commercial hexanes gradient @ 100 mL/min) to give the title compound (300 mg, 1.32 mmol, 35.18% yield) as a yellow solid. MS (M+H) ⁺ = 227.2

Step 4. Synthesis of methyl (R)-3-(2-((tert-butyldimethylsilyl)oxy)ethoxy)-4-((5,7,8-trimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)benzoate (7)

The title compound (0.3 g, 552.67 μmol, 83.51% yield, 95% purity) was obtained as a yellow solid by a similar method to step 5 of Example 9. MS (M+H) ⁺ = 516.4

Step 5. Synthesis of (R)-3-(2-hydroxyethoxy)-4-((5,7,8-trimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)benzoic acid (8)

To a solution of methyl (R)-3-(2-((tert-butyldimethylsilyl)oxy)ethoxy)-4-((5,7,8-trimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)benzoate (300 mg, 581.76 μmol) in THF (2 mL) and MeOH (2 mL) was added NaOH (2 M, 2 mL), and the mixture was stirred at 20 °C for 16 h. The major peak of the desired mass was identified by LCMS, and the mixture was dissolved in H ₂ O (20 mL), pH = 5-6 by 1 M HCl, the suspension was filtered, and the filter cake was dried to obtain the title compound (100 mg, 258.14 μmol, 44.37% yield) as a yellow solid. MS (M+H) ⁺ =388.1

Step 6. Synthesis of N-((1r,4R)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-(2-hydroxyethoxy)-4-(((R)-5,7,8-trimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)benzamide (Compound 15)

The title compound (21 mg, 26.80 μmol, 23.07% yield, 98% purity) was obtained as a white solid by a similar method to step 7 of Example 9. MS(M+H) ⁺ = 768.5

^1H NMR (400 MHz, DMSO _- d6 ) δ = 10.79 (s, 1H), 8.56 (d, J = 8.5 Hz, 1H), 8.11 (s, 1H), 8.07 (d, J = 7.9 Hz, 1H), 7.89 (s, 1H), 7.55 (dd, J = 1.6, 8.7 Hz, 1H), 7.51 (d, J = 1.5 Hz, 1H), 6.95 (d, J = 8.5 Hz, 2H), 6.57 (d, J = 8.5 Hz, 2H), 5.64 (t, J = 5.5 Hz, 1H), 5.27 (t, J = 5.9 Hz, 1H), 4.36 (q, J = 6.8 Hz, 1H), 4.17 (t, J = 4.6 Hz, 2H), 3.90 - 3.82 (m, 2H), 3.81 - 3.73 (m, 1H), 3.69 (dd, J = 5.0, 10.5 Hz, 1H), 3.30 (s, 3H), 3.14 (s, 3H), 3.03 - 2.85 (m, 4H), 2.70 - 2.62 (m, 1H), 2.55 - 2.48 (m, 1H), 2.41 - 2.32 (m, 1H), 2.29 - 2.19 (m, 2H), 2.18 - 2.10 (m, 1H), 2.09 - 2.02 (m, 1H), 1.99 - 1.91 (m, 2H), 1.90 - 1.78 (m, 4H), 1.60 - 1.52 (m, 1H), 1.45 - 1.33 (m, 7H), 1.27 - 1.16 (m, 2H).

Example 16. Synthesis of N-((1r,4R)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-4-(((R)-8-isopropyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzamide (Compound 16)

Step 1. Synthesis of methyl isopropyl-D-alaninate (2)

To a solution of methyl D-alaninate (7 g, 50.15 mmol, HCl salt) in DCM (150 mL) were added acetone (6.32 g, 108.82 mmol, 8 mL) and NaOAc (10 g, 121.90 mmol) at 20 °C, and the mixture was stirred at 20 °C for 1 h. Then, NaBH(OAc) ₃ (30 g, 141.55 mmol) was added, and the resulting mixture was stirred at 20 °C for 15 h. The peak of the target mass was confirmed by LCMS. The reaction mixture was diluted with H ₂ O (100 mL), adjusted to pH = 8~9 with NaHCO ₃ (sat. aq, 300 mL) at 0 °C, and the mixture was extracted with DCM (300 mL × 2). The mixed organic layer was washed with brine (300 mL × 2), dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure to obtain the title compound (4 g, crude) as a pale yellow oil. MS (M+H) ⁺ = 146.3

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 3.62 (s, 3H), 3.35 (q, J = 7.0 Hz, 1H), 2.70 - 2.59 (m, 1H), 2.22 - 1.75 (m, 1H), 1.15 (d, J = 7.0 Hz, 3H), 0.98 - 0.86 (m, 6H)

Step 2. Synthesis of methyl N-(2-chloro-5-nitropyrimidin-4-yl)-N-isopropyl-D-alaninate (4)

To a solution of methyl isopropyl-D-alaninate (2.8 g, 19.28 mmol) in acetone (40 mL) were added 2,4-dichloro-5-nitro-pyrimidine (3.50 g, 18.04 mmol) and K ₂ CO ₃ (6.72 g, 48.62 mmol) at 20 °C. The mixture was stirred at 20 °C under CN ₂ for 16 h. The target mass peak (67%) was identified by LCMS. The reaction mixture was filtered. The filter cake was washed with EtOAc (150 mL). The filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (Biotage; 40 g SepaFlash® silica flash column, eluent of 8–10% EtOAc: petroleum ether gradient, 100 mL/min) to give the title compound (3.7 g, 12.22 mmol, 63.38% yield) as a pale yellow solid. MS (M+H) ⁺ = 303.1

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 8.78 (s, 1H), 4.61 (q, J = 6.6 Hz, 1H), 3.63 (s, 3H), 3.53 - 3.41 (m, 1H), 1.51 (d, J = 6.6 Hz, 3H), 1.35 - 1.20 (m, 6H)

Step 3. Synthesis of (R)-2-chloro-8-isopropyl-7-methyl-7,8-dihydropteridin-6(5H)-one (5)

To a solution of methyl N-(2-chloro-5-nitropyrimidin-4-yl)-N-isopropyl-D-alaninate (3 g, 9.91 mmol) in HOAc (40 mL) was added Fe (3.60 g, 64.46 mmol). The mixture was stirred at 60 °C for 16 h. The main peak of the target mass was identified by LCMS. The reaction mixture was filtered, and the filtrate was concentrated under reduced pressure to remove HOAc. Then, Na ₂ CO ₃ (aqueous solution, 60 mL) was added to adjust the pH to 8–9. The mixture was extracted with EtOAc (200 mL × 3). The combined organic layer was washed with brine (200 mL × 2), dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure to obtain the title compound (2.1 g, crude) as a pale yellow solid. MS (M+H) ⁺ = 241.0

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.77 (s, 1H), 7.61 (s, 1H), 4.46 - 4.37 (m, 1H), 4.29 (q, J = 6.7 Hz, 1H), 1.33 - 1.30 (m, 6H), 1.29 - 1.27 (m, 3H)

Step 4. Synthesis of (R)-2-chloro-8-isopropyl-5,7-dimethyl-7,8-dihydropteridin-6(5H)-one (6)

To a solution of (R)-2-chloro-8-isopropyl-7-methyl-7,8-dihydropteridin-6(5H)-one (1.5 g, 6.23 mmol) in DMF (20 mL) were added MeI (2.28 g, 16.06 mmol, 1 mL) and K ₂ CO ₃ (2.2 g, 15.92 mmol) at 0 °C. The mixture was then stirred at 25 °C for 3 h. The major peak of the desired mass was identified by LCMS. The reaction mixture was diluted with H ₂ O (40 mL) at 0 °C and extracted with EtOAc (80 mL × 2). The combined organic layer was washed with brine (80 mL × 3), dried over Na ₂ SO ₄ , filtered, and the filtrate was concentrated under reduced pressure to obtain the title compound (1.5 g, crude) as a pale yellow solid. MS (M+H) ⁺ = 255.1

¹ H NMR (400 MHz, DMSO- d ₆ ) δ = 7.88 (s, 1H), 4.51 - 4.36 (m, 2H), 3.23 (s, 3H), 1.36 - 1.23 (m, 9H)

Step 5. Synthesis of (R)-4-((8-isopropyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoic acid (8)

To a solution of (R)-2-chloro-8-isopropyl-5,7-dimethyl-7,8-dihydropteridin-6(5H)-one (1.5 g, 5.89 mmol) in EtOH (8 mL) were added 4-amino-3-methoxy-benzoic acid (1.48 g, 8.83 mmol) and a solution of HCl (12 M, 1.9 mL) in H ₂ O (40 mL) at 20 °C. The mixture was stirred at 100 °C for 16 h. The peak of the desired mass was identified by LCMS. The reaction mixture was stirred at 20 °C for 1 h and then filtered. The filtrate was concentrated under reduced pressure to give the title compound (1.7 g, crude) as a pale yellow solid. MS (M+H) ⁺ = 386.2

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 9.73 - 9.59 (m, 1H), 8.14 (d, J = 8.3 Hz, 1H), 7.96 (s, 1H), 7.69-7.61 (m, 1H), 7.59 - 7.55 (m, 1H), 4.59 - 4.51(m, 2H), 3.94 (s, 3H), 3.20 (s, 3H), 1.42 (d, J = 6.7 Hz, 3H), 1.36 (t, J = 7.2 Hz, 6H)

Step 6. Synthesis of 2,6-bis(benzyloxy)-3-(4-nitrophenyl)pyridine (12)

A mixture of 2,6-bis( _benzyloxy )-3-bromopyridine (20 g, 54.02 mmol), (4-nitrophenyl)boronic acid (20.0 g, 119.81 mmol), K ₃ PO ₄ (28.67 g, 135.05 mmol), Pd(dppf)Cl ₂ (3.9 g, 5.33 mmol) in dioxane (400 mL) and H 2 O (80 mL) was degassed and purged three times with N ₂ , and the mixture was stirred at 110 °C under CN ₂ for 16 h. The target mass peak (56%) was identified by LCMS. The reaction mixture was filtered. The filtrate was diluted with H ₂ O (300 mL) and extracted with EtOAc (800 mL × 2). The mixed organic layer was washed with brine (500 mL × 3), dried over anhydrous Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (Biotage; 220 g SepaFlash® silica flash column, eluent of 5–10% EtOAc: petroleum ether gradient, 150 mL/min) to give the title compound (20 g, 48.49 mmol, 89.77% yield) as a yellow solid. MS (M+H) ⁺ = 413.2

¹ H NMR (400 MHz, DMSO- d ₆ ) δ = 8.26 - 8.21 (m, 2H), 7.90 - 7.83 (m, 3H), 7.47 - 7.29 (m, 10H), 6.62 (d, J = 8.2 Hz, 1H), 5.43 (d, J = 16.0) Hz, 4H)

Step 7. Synthesis of 3-(4-aminophenyl)piperidine-2,6-dione (13)

A solution of Pd(OH) ₂ /C (2 g, 24.25 mmol, 20% purity) in MeOH (200 mL) was slowly added to a solution of 2,6-dibenzyloxy-3-(4-nitrophenyl) pyridine (10 g, 24.25 mmol) in THF (200 mL) under N ₂ , and the mixture was stirred at 30 °C under CH ₂ (45 psi) for 50 h. The major peak of the desired mass was identified by LCMS. The mixture was filtered, and the filter cake was washed with THF (1000 mL). The filtrate was concentrated under reduced pressure to give the title compound (5 g, crude) as a yellow solid. MS (M+H) ⁺ = 205.1

¹ H NMR (400 MHz, DMSO- d ₆ ) δ 6.93 - 6.79 (m, 2H), 6.57 - 6.44 (m, 2H), 4.98 (s, 2H), 3.68 - 3.55 (m, 1H), 2.65 - 2.55 (m, 1H), 2.50 - 2.40 (m, 1H), 2.13 - 1.92 (m, 2H)

Step 8. Synthesis of benzyl ((1r,4r)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)carbamate (15)

To a solution of 3-(4-aminophenyl)piperidine-2,6-dione (1.2 g, 5.88 mmol) in DCM (30 mL) and DMF (5 mL) were added benzyl ((1r,4r)-4-(4-formylpiperidin-1-yl)cyclohexyl)carbamate (1.42 g, 4.11 mmol) and HOAc (314.70 mg, 5.24 mmol, 300 μL). The mixture was stirred at 20 °C for 1 h. Then, NaBH(OAc) ₃ (5 g, 23.59 mmol) was added at 0 °C, and the mixture was stirred at 20 °C for 15 h. The target mass peak (67%) was identified by LCMS. The reaction mixture was diluted with H ₂ O (20 mL) and DCM (40 mL), and then adjusted to pH = 9 with NaHCO ₃ (saturated aqueous solution, 50 mL). The suspension was extracted with DCM (50 mL × 2). The combined organic layer was washed with brine (50 mL × 2), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure. The product was triturated with a solvent (DCM: MTBE = 1:2; 45 mL) at 20 ^o C for 1 h. The mixture was filtered. The filter cake was dried under reduced pressure to obtain the product (1.3 g). The filtrate was concentrated under reduced pressure. The residue was purified by prep-HPLC (column: Phenomenex luna C18 150 x 25 mm x 10 μm; mobile phase: [H ₂ O (0.1% TFA) - ACN]; gradient: 15% - 45% B over 15.0 min, column Temp: 30 °C). The eluate was lyophilized to give the product as a yellow solid (500 mg). The two batches were combined to give the title compound as a yellow solid (1.8 g, 3.38 mmol, 57.51% yield). MS (M+H) ⁺ = 533.4

¹ H NMR (400 MHz, DMSO-d ₆ ) δ = 10.83 - 10.64 (m, 1H), 7.49 - 7.26 (m, 5H), 7.25 - 7.09 (m, 1H), 6.95 - 6.74 (m, 2H), 6.57 - 6.44 (m, 2H), 5.62 - 5.51 (m, 1H), 4.99 (s, 2H), 3.68 - 3.58 (m, 1H), 3.28-3.16 (m, 1H), 2.91 - 2.74 (m, 4H), 2.64 - 2.52 (m, 2H), 2.50 - 2.39 (m, 1H), 2.28 - 1.91 (m, 5H), 1.87 - 1.62 (m, 6H), 1.52 - 1.41 (m, 1H), 1.29 - 1.07 (m, 5H)

Step 9. Synthesis of 3-(4-(((1-((1r,4r)-4-aminocyclohexyl)piperidin-4-yl)methyl)amino)phenyl)piperidine-2,6-dione (9)

A mixture of benzyl ((1r,4r)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)carbamate (300 mg, 563.20 μmol) in TFA (6 mL) was stirred at 50 °C under CN ₂ for 2 h. The main peak of the desired mass was confirmed by LCMS. The reaction mixture was concentrated under reduced pressure to obtain the title compound (290 mg, crude, TFA) as a green oil. MS (M+H) ⁺ = 399.3

Step 10. Synthesis of N-((1r,4R)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-4-(((R)-8-isopropyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzamide (Compound 16)

To a solution of (R)-4-((8-isopropyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoic acid (80 mg, 207.57 μmol) in DMF (2 mL) were added HATU (95 mg, 249.85 μmol), DIPEA (222.60 mg, 1.72 mmol, 300 μL), and the mixture was stirred at 20 °C for 0.5 h, then a solution of 3-(4-(((1-((1r,4r)-4-aminocyclohexyl)piperidin-4-yl)methyl)amino)phenyl)piperidine-2,6-dione (95 mg, 185.34 μmol, TFA) in DMF (1 mL) was added at 0 °C, and the resulting mixture was cooled to 20 °C. ₂ was stirred for 15.5 h. The target mass peak (38%) was confirmed by LCMS. The reaction mixture was diluted with H ₂ O (15 mL) and extracted with EtOAc (30 mL × 2). The mixed organic layer was washed with NaHCO ₃ (aq, 30 mL × 2) and brine (30 mL × 2), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by prep-HPLC (column: Phenomenex Luna C18 150 x 25 mm x10 μm; mobile phase: [H ₂ O (0.1% TFA) - ACN]; gradient: 0% - 28% B over 15.0 min, column Temp: 30 °C) and the eluate was lyophilized. Afterwards, the product was diluted with DCM (10 mL) and adjusted to pH = 7~8 by adding NaHCO ₃ (sat. aq, 10 mL), and the mixture was extracted with DCM (10 mL × 2). The mixed organic layer was concentrated under reduced pressure and lyophilized to obtain the title compound (20.1 mg, 24.67 μmol, 11.88% yield, 94% purity) as a white solid. MS (M+H) ⁺ = 766.5

^1H NMR (400 MHz, DMSO-d ₆ ) δ = 10.74 (s, 1H), 8.45 (d, J = 8.3 Hz, 1H), 8.08 (s, 1H), 7.89 (s, 1H), 7.65 - 7.60 (m, 1H), 7.52 - 7.41 (m, 2H), 6.88 (d, J = 8.3 Hz, 2H), 6.51 (d, J = 8.4 Hz, 2H), 5.66 - 5.53 (m, 1H), 4.70 - 4.56 (m, 1H), 4.42 - 4.30 (m, 1H), 3.94 (s, 3H), 3.77 - 3.68 (m, 1H), 3.64 - 3.59 (m, 1H), 3.23 (s, 3H), 2.90 - 2.80 (m, 3H), 2.64 - 2.51 (m, 1H), 2.48 - 2.36 (m, 4H), 2.27 - 2.12 (m, 2H), 2.08 - 1.97 (m, 2H), 1.92 - 1.85 (m, 2H), 1.84 - 1.72 (m, 4H), 1.58 - 1.45 (m, 1H), 1.38 - 1.32 (m, 6H), 1.31 - 1.27 (m, 3H), 1.24 (d, J = 6.7 Hz, 3H), 1.19 - 1.08 (m, 2H)

Example 17. Synthesis of N-((1r,4R)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-(2-hydroxyethoxy)-4-(((R)-8-isopropyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)benzamide (Compound 17)

Step 1. Synthesis of methyl 3-(2-((tert-butyldimethylsilyl)oxy)ethoxy)-4-nitrobenzoate (2)

To a solution of methyl 3-hydroxy-4-nitrobenzoate (2 g, 10.14 mmol) and (2-bromoethoxy)(tert-butyl)dimethylsilane (3.64 g, 15.22 mmol) in DMF (40 mL) was added K ₂ CO ₃ (2.80 g, 20.29 mmol), and the mixture was stirred at 100 °C for 14 h. The mixture was diluted with water (50 mL) and extracted with EtOAc (30 mL x 2). The combined organic layer was washed with brine (10 mL x 2), dried over Na ₂ SO ₄ , and The residue was filtered. The filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (12 g SepaFlash® silica flash column, eluent of 20% EtOAc/Commercial hexanes gradient @ 200 mL/min) to obtain the title compound (3.98 g, crude) as a yellow solid.

Step 2. Synthesis of methyl 4-amino-3-(2-((tert-butyldimethylsilyl)oxy)ethoxy)benzoate (3)

Solution 1: Reg ₁ : Methyl 3-(2-((tert-butyldimethylsilyl)oxy)ethoxy)-4-nitrobenzoate (3.98 g, 11.20 mmol) in MeOH (19.9 mL) and THF (19.9 mL). Solution 1 was pumped by Pump 1 (S ₁ , P1, 0.4 mL/min) and flowed into Reactor 1 (FLR ₁ , SS, Fixed bed, 6.350 (1/4") mm, 1.0 mL, 50.0 °C). The fixed bed (Fixed bed, named FLR ₁ , volume 5 mL) was completely packed with granular catalyst Pt/C (1.5 g, 1% purity). The H ₂ pressure controller was adjusted to 1.5 MPa, and the H ₂ flow rate was (WuXi-EHS, 10 mL/min). The reaction mixture was then collected from the reactor, and the formation of a new spot was confirmed by TLC (Petroleum ether:EtOAc=5:1). The mixture was concentrated under reduced pressure to obtain the title compound (3.3 g, crude) as a yellow oil. MS(M+H) ⁺ =326.2

Step 3. Synthesis of methyl (R)-3-(2-((tert-butyldimethylsilyl)oxy)ethoxy)-4-((8-isopropyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)benzoate (5)

To a solution of methyl 4-amino-3-(2-((tert-butyldimethylsilyl)oxy)ethoxy)benzoate (330 mg, 1.01 mmol), (R)-2-chloro-8-isopropyl-5,7-dimethyl-7,8-dihydropteridin-6(5H)-one (0.2 g, 785.19 μmol) and K ₃ PO ₄ (500.01 mg, 2.36 mmol) in dioxane (6 mL) were added Pd ₂ (dba) ₃ (28.76 mg, 31.41 μmol) and Xantphos (27.26 mg, 47.11 μmol) under N ₂ , and the mixture was stirred at 100 °C under N ₂ for 14 h. The peak of the target mass was identified by LCMS. The mixture was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (12 g SepaFlash® silica flash column, Eluent of 30% EtOAc/Petroleum ether gradient @ 200 mL/min) to give the title compound (270 mg, 461.81 μmol, 58.82% yield, 93% purity) as a yellow oil. MS(M+H) ⁺ = 544.4

Step 4. Synthesis of (R)-3-(2-hydroxyethoxy)-4-((8-isopropyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)benzoic acid (6)

To a solution of methyl (R)-3-(2-((tert-butyldimethylsilyl)oxy)ethoxy)-4-((8-isopropyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)benzoate (270 mg, 496.57 μmol) in THF (3 mL) and MeOH (3 mL) was added NaOH (2 M, 3 mL), and the mixture was stirred at 20 °C for 14 h. The peak of the desired mass was identified by LCMS. The mixture was concentrated under reduced pressure. The product was diluted with 1 N HCl (5 mL) and extracted with DCM (30 mL x 2). The combined organic layers were washed with brine (10 mL x 2), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure. The aqueous phase was concentrated under reduced pressure to obtain the title compound (0.3 g, crude) as a yellow solid. MS(M+H) ⁺ = 416.3

Step 5. Synthesis of N-((1r,4R)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-(2-hydroxyethoxy)-4-(((R)-8-isopropyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)benzamide (Compound 17)

The title compound (10.5 mg, 12.14 μmol, 8.89% yield, 92% purity) was obtained as a white solid by a similar method to step 6 of Example 16. MS(M+H) ⁺ = 796.6

^1H NMR (400 MHz, DMSO-d ₆ ) δ = 10.72 (s, 1H), 8.45 (d, J = 8.4 Hz, 1H), 8.07 (s, 1H), 8.00 (br d, J = 7.4 Hz, 1H), 7.89 (s, 1H), 7.51 - 7.42 (m, 2H), 6.88 (d, J = 8.5 Hz, 2H), 6.51 (d, J = 8.4 Hz, 2H), 5.63 - 5.51 (m, 1H), 5.20 (t, J = 5.8 Hz, 1H), 4.72 - 4.58 (m, 1H), 4.36 (q, J = 6.5 Hz, 1H), 4.11 (t, J = 4.4 Hz, 2H), 3.82 - 3.75 (m, 2H), 3.75 - 3.66 (m, 1H), 3.65 - 3.59 (m, 1H), 3.23 (s, 3H), 2.91 - 2.79 (m, 4H), 2.63 - 2.56 (m, 1H), 2.46 - 2.39 (m, 1H), 2.30 - 2.22 (m, 1H), 2.22 - 2.11 (m, 2H), 2.10 - 2.02 (m, 1H), 2.01 - 1.96 (m, 1H), 1.93 - 1.85 (m, 2H), 1.83 - 1.68 (m, 4H), 1.58 - 1.43 (m, 1H), 1.41 - 1.28 (m, 10H), 1.24 (d, J = 6.8 Hz, 3H), 1.21 - 1.06 (m, 2H)

Example 18. Synthesis of 5-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-4-methoxypicolinamide (Compound 18)

Step 1. Synthesis of methyl (R)-5-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-4-methoxypicolinate (3)

A mixture of (R)-2-amino-8-cyclopentyl-5,7-dimethyl-7,8-dihydropteridin-6(5H)-one (300 mg, 1.01 mmol), methyl 5-bromo-4-methoxy-pyridine-2-carboxylate (272.68 mg, 1.11 mmol), Pd ₂ (dba) ₃ (92.25 mg, 100.74 μmol), Xantphos (116.59 mg, 201.49 μmol), and K ₃ PO ₄ (427.70 mg, 2.01 mmol) in dioxane (10 mL) was degassed and purged three times with N ₂ , and the mixture was stirred at 100 °C under CN ₂ for 16 h. The main peak of the target mass was identified by LCMS. The mixture was diluted with H ₂ O (100 mL), extracted with EtOAc (50 mL x 3), and the combined organic layers were washed with brine (100 mL), dried over Na ₂ SO ₄ , filtered, and the filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (20 g SepaFlash® silica flash column, Eluent of 0–100% EtOAc/Petroleum ether gradient @ 80 mL/min) to give the title compound (0.3 g, 682.35 μmol, 67.73% yield, 97% purity) as a yellow solid. MS (M+H) ⁺ = 427.1

Step 2. Synthesis of (R)-5-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-4-methoxypicolinic acid (4)

To a solution of methyl (R)-5-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-4-methoxypicolinate (0.3 g, 703.45 μmol) in MeOH (3 mL) and THF (3 mL) was added a solution of NaOH (112.55 mg, 2.81 mmol) in H ₂ O (3 mL), and the resulting mixture was stirred at 20 °C for 1 h. The peak of the target mass (100%) was confirmed by LCMS. The mixture was concentrated under reduced pressure, diluted with H ₂ O (20 mL), and the aqueous layer was adjusted to pH = 6 and concentrated under reduced pressure to obtain the title compound (0.5 g, crude) as a white solid. MS (M+H) ⁺ = 413.2

Step 3. Synthesis of 5-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-4-methoxypicolinamide (Compound 18)

To a solution of (R)-5-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-4-methoxypicolinic acid (60 mg, 145.48 μmol) in DMF (1 mL) were added HATU (65.00 mg, 170.95 μmol) and DIPEA (45.39 mg, 351.18 μmol, 61.17 μL), and the mixture was stirred at 20 °C for 1 h. 3-(4-(((1-((1r,4r)-4-aminocyclohexyl)piperidin-4-yl)methyl)amino)phenyl)piperidine-2,6-dione (60 mg, 117.06 μmol, TFA) was added, and the mixture was stirred at 20 °C for 1 h. The target mass peak (65%) was confirmed by LCMS. The mixture was diluted with H ₂ O (20 mL), extracted with EtOAc (10 mL x 3), the combined organic layers were washed with brine (20 mL), dried over Na ₂ SO ₄ , filtered, and the filtrate was concentrated under reduced pressure. The residue was purified by prep-HPLC (column: Phenomenex Luna C18 150*25 mm*10 um; mobile phase: [H ₂ O (0.1% TFA)-ACN]; gradient: 0%-28% B over 15.0 min), and the eluate was lyophilized. The product was dissolved in H ₂ O (20 mL) and adjusted to pH=8~9 with NaHCO ₃ . The resulting suspension was extracted with EtOAc (10 mL x 3), the combined organic layers were dried over Na ₂ SO ₄ , filtered, the filtrate was concentrated under reduced pressure, and the residue was lyophilized. The product was purified by prep-HPLC (column: Waters xbridge 150*25 mm 10 μm; mobile phase: [H ₂ O (10 mM NH ₄ HCO ₃ )-ACN]; gradient: 30%-60% B over 10.0 min), and the eluate was lyophilized to obtain the title compound as a white solid (19.6 mg, 24.47 μmol, 20.90% yield, 99% purity). MS(M+H) ⁺ =793.5

^1H NMR (400 MHz, DMSO-d ₆ ) δ = 10.75 (s, 1H), 9.26 (s, 1H), 8.28 (d, J = 8.6 Hz, 1H), 7.88 (s, 1H), 7.84 (s, 1H), 7.65 (s, 1H), 6.90 (d, J = 8.3 Hz, 2H), 6.52 (d, J = 8.3 Hz, 2H), 5.60 (t, J = 5.3 Hz, 1H), 4.42 - 4.27 (m, 2H), 4.00 (s, 3H), 3.78 - 3.69 (m, 1H), 3.64 (dd, J = 5.3, 10.4 Hz, 1H), 3.25 (s, 3H), 2.91 - 2.80 (m, 4H), 2.70 - 2.58 (m, 2H), 2.37 - 2.26 (m, 1H), 2.22 - 2.07 (m, 3H), 2.05 - 1.94 (m, 2H), 1.92 - 1.85 (m, 3H), 1.84 - 1.69 (m, 8H), 1.61 - 1.49 (m, 3H), 1.47 - 1.31 (m, 4H), 1.23 (d, J = 6.8 Hz, 3H), 1.21 - 1.10 (m, 2H).

Example 19. 5-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-4-(2-hydroxyethoxy)picolinamide (Compound 19)

Step 1. Synthesis of 5-bromo-4-hydroxypicolinic acid (2)

A mixture of methyl 5-bromo-4-methoxy-pyridine-2-carboxylate (5 g, 20.32 mmol) in HBr (74.50 g, 368.30 mmol, 50 mL, 40% purity) was stirred at 90 °C for 48 h. The main peak of the target mass was identified by LCMS, and the mixture was concentrated under reduced pressure to obtain the title compound (4.5 g, crude) as a yellow solid. MS (M+H) ⁺ = 218.0, 220.0

Step 2. Synthesis of methyl 5-bromo-4-hydroxypicolinate (3)

To a solution of 5-bromo-4-hydroxy-pyridine-2-carboxylic acid (4.5 g, 20.64 mmol) in MeOH (50 mL) was added H ₂ SO ₄ (2.02 g, 20.64 mmol, 1.10 mL), and the resulting mixture was stirred at 70 °C for 14 h. The main peak of the desired mass was identified by LCMS, and the mixture was concentrated under reduced pressure, and the residue was triturated with H ₂ O (50 mL), filtered, and the filter cake was dried to obtain the title compound (3.5 g, 15.08 mmol, 73.08% yield) as a white solid. MS (M+H) ⁺ = 232.0, 234

Step 3. Synthesis of methyl 5-bromo-4-(2-((tert-butyldimethylsilyl)oxy)ethoxy)picolinate (4)

To a solution of methyl 5-bromo-4-hydroxy-pyridine-2-carboxylate (1.3 g, 5.60 mmol) and 2-bromoethoxy-tert-butyl-dimethyl-silane (1.61 g, 6.72 mmol) in DMF (10 mL) was added K ₂ CO ₃ (2.32 g, 16.81 mmol), and the mixture was stirred at 90 °C for 14 h. The major peak of the desired mass was identified by LCMS. The mixture was diluted with H ₂ O (100 mL) and extracted with EtOAc (50 mL x 3). The combined organic layer was washed with brine (100 mL), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (20 g SepaFlash® silica flash column, eluent of 0–20% EtOAc/Commercial hexanes gradient @ 100 mL/min) to give the title compound (1.1 g, 2.82 mmol, 50.30% yield) as a white solid. MS (M+H) ⁺ = 390.1, 392.1

Step 4. Synthesis of methyl (R)-4-(2-((tert-butyldimethylsilyl)oxy)ethoxy)-5-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)picolinate (6)

To a solution of methyl 5-bromo-4-(2-((tert-butyldimethylsilyl)oxy)ethoxy)picolinate (300 mg, 768.55 μmol) and (R)-2-amino-8-cyclopentyl-5,7-dimethyl-7,8-dihydropteridin-6(5H)-one (200.84 mg, 768.55 μmol) in dioxane (10 mL) were added BrettPhos Pd G ₃ (69.67 mg, 76.86 μmol) and Cs ₂ CO ₃ (751.23 mg, 2.31 mmol), and the resulting mixture was stirred at 100 °C under CN ₂ for 16 h. The target mass peak (53%) was confirmed by LCMS. The mixture was filtered and concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (50 g SepaFlash® silica flash column, eluent of 0–50% EtOAc/Commercial hexanes gradient @ 100 mL/min) to give the title compound (0.25 g, 438.02 μmol, 56.99% yield) as a yellow solid. MS (M+H) ⁺ = 571.4

Step 5. Synthesis of (R)-5-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-4-(2-hydroxyethoxy)picolinic acid (7)

To a solution of methyl (R)-4-(2-((tert-butyldimethylsilyl)oxy)ethoxy)-5-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)picolinate (250 mg, 438.02 μmol) in THF (2 mL) and MeOH (2 mL) was added NaOH (2 M, 2 mL), and the mixture was stirred at 20 °C for 14 h. The peak of the target mass (96%) was identified by LCMS, and the mixture was dissolved in H ₂ O (20 mL), pH=5-6 with 1 M HCl, the suspension was filtered, and the filter cake was dried to obtain the title compound (150 mg, 339.01 μmol, 77.40% yield) as a yellow solid. MS (M+H) ⁺ =443.3

Step 6. 5-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-4-(2-hydroxyethoxy)picolinamide (Compound 19)

The title compound (14.1 mg, 16.62 μmol, 14.71% yield, 97% purity) was obtained as a white solid by a similar method to step 3 of Example 18. MS(M+H) ⁺ = 823.5

^1H NMR (400 MHz, DMSO-d ₆ ) δ = 10.76 (s, 1H), 9.35 (s, 1H), 8.21 (s, 1H), 7.90 (s, 1H), 7.60 (s, 1H), 6.90 (d, J = 8.3 Hz, 2H), 6.53 (d, J = 7.9 Hz, 2H), 5.77 - 5.52 (m, 1H), 5.24 (t, J = 6.1 Hz, 1H), 4.55 - 4.42 (m, 1H), 4.32 (q, J = 6.5 Hz, 1H), 4.20 (t, J = 4.3 Hz, 2H), 3.83 - 3.69 (m, 3H), 3.64 (dd, J = 5.1, 10.8 Hz, 1H), 3.25 (s, 3H), 2.97 - 2.82 (m, 3H), 2.70 - 2.58 (m, 2H), 2.49 - 2.40 (m, 2H), 2.18 - 2.07 (m, 2H), 2.06 - 1.85 (m, 8H), 1.82 - 1.67 (m, 7H), 1.64 - 1.32 (m, 8H), 1.29 - 1.17 (d, J = 6.8 Hz, 4H).

Example 20. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1R,4R)-4-(4-(((4-((R)-2,6-dioxopiperidin-3-yl-3-d)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 20)

Step 1. Synthesis of methyl 2-cyano-2-(4-nitrophenyl)acetate (3)

1-Chloro-4-nitrobenzene (30 g, 190.41 mmol, 23.11 mL) was slowly added to a solution of methyl 2-cyanoacetate (33.02 g, 333.22 mmol, 29.40 mL) and K ₂ CO ₃ (46.05 g, 333.22 mmol) in DMF (300 mL) at 120 °C, and the mixture was stirred at 120 °C for 14 h. The target spot was identified by TLC (Petroleum ether:EtOAc=3:1). The mixture was diluted with water (50 mL) and extracted with EtOAc (20 mL x 2). The combined organic layer was washed with water (50 mL), dried over Na ₂ SO _{4 ,} and It was filtered. The filtrate was concentrated under reduced pressure. The product was diluted with water (300 mL) and the pH was adjusted to ~2 with 15% H ₂ SO _{4 .} The suspension was filtered. The filter cake was washed with water (50 mL) and dried under reduced pressure. The product was diluted with DCM (150 mL) and stirred at 20 °C for 0.5 h. The suspension was filtered, and the filter cake was washed with DCM (20 mL). The filtrate was concentrated under reduced pressure to give the title compound (17.47 g, 79.34 mmol, 41.67% yield) as a red solid.

Step 2. Synthesis of dimethyl 2-cyano-2-(4-nitrophenyl)pentanedioate (5)

To a solution of methyl 2-cyano-2-(4-nitrophenyl)acetate (17.47 g, 79.34 mmol) in THF (350 mL) and NMP (15 mL) were added TEA (16.08 g, 158.94 mmol, 22.12 mL) and methyl acrylate (6.45 g, 74.92 mmol, 6.75 mL), and the mixture was stirred at 60 °C under CN ₂ for 14 h. TLC (Petroleum ether:EtOAc=3:1) confirmed complete consumption of the starting material and the formation of a new spot. The mixture was diluted with water (100 mL), extracted with EtOAc (100 mL x 2). The combined organic layer was washed with brine (100 mL x 2), dried over Na ₂ SO _{4 ,} and The residue was filtered. The filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (120 g SepaFlash® silica flash column, eluent of 30% EtOAc/Petroleum ether gradient @ 200 mL/min) to give the title compound (13.35 g, 43.59 mmol, 54.94% yield) as a yellow oil.

Step 3. Synthesis of 3-(4-nitrophenyl)piperidine-2,6-dione (6)

To a solution of dimethyl 2-cyano-2-(4-nitrophenyl)pentanedioate (13.35 g, 43.59 mmol) in AcOH (120 mL) was slowly added H ₂ SO ₄ (10.72 g, 109.30 mmol, 5.83 mL), and the mixture was stirred at 110 °C for 14 h. The peak of the target mass was identified by LCMS. The mixture was slowly poured into water (200 mL) and stirred at 20 °C for 0.5 h. The suspension was filtered, and the filter cake was washed with water (50 mL). The filter cake was dried under reduced pressure. The product was diluted with water (80 mL), and the pH was adjusted to 8 with saturated NaHCO ₃ . The suspension was filtered, and the filter cake was washed with water (50 mL) and DCM (50 mL). The filter cake was collected to obtain product A. The filtrate was extracted with DCM (30 mL x 3), and the mixed organic layer was dried over Na ₂ SO ₄ It was filtered. The filtrate was concentrated under reduced pressure to obtain product B. Product A and product B were mixed to obtain the title compound (4.03 g, 17.21 mmol, 39.48% yield) as a yellow solid.

Step 4. Synthesis of 5-amino-4-(4-nitrophenyl)-5-oxopentanoic acid-4-d (7)

To a solution of 3-(4-nitrophenyl)piperidine-2,6-dione (4.03 g, 17.21 mmol) in THF (180 mL) was added LiHMDS (1 M, 43.6 mL) at -78 °C in CN ₂ , and the mixture was stirred at -78 °C in CN ₂ for 1 h. Then, D ₂ O (6.89 g, 344.14 mmol) was added at -78 °C in CN ₂ , and the mixture was warmed to 20 °C and stirred at 20 °C for 14 h. The peak of the target mass was identified by LCMS. The mixture was filtered, and the filter cake was washed with THF (30 mL). The filter cake was dried under reduced pressure. The product was diluted with water (50 mL) and DCM (100 mL). The mixture was adjusted to pH = ~3 with 1 N HCl and then filtered. The filter cake was washed with DCM (10 mL) and water (10 mL), and then dried under reduced pressure to obtain 5-amino-4-(4-nitrophenyl)-5-oxopentanoic acid-4-d (1.94 g, crude) as a yellow solid. The filtrate was extracted with DCM (50 mL x 3) and EtOAc (20 mL x 3). The mixed organic layer was dried over Na ₂ SO ₄ It was filtered. The filtrate was concentrated under reduced pressure to obtain the title compound (1.43 g, crude) as a yellow solid.

Step 5. Synthesis of 3-(4-nitrophenyl)piperidine-2,6-dione-3-d (8)

To a solution of 5-amino-4-(4-nitrophenyl)-5-oxopentanoic acid-4-d (1.5 g, 5.92 mmol) in DCM (50 mL), THF (25 mL) and DMF (8 mL) was slowly added SOCl ₂ (3.47 g, 29.12 mmol, 2.12 mL) under -50 °CN ₂ , and the mixture was stirred under -50 °CN ₂ for 1 h. Then, Py (2.35 g, 29.73 mmol, 2.40 mL) was added under -50 °CN ₂ , and the mixture was stirred under -50 °CN ₂ for 30 min. Finally, TEA (3.01 g, 29.71 mmol, 4.13 mL) was added under -50 °CN ₂ , and the mixture was stirred under -50 °CN ₂ for 1 h. The target spot was identified by TLC (Petroleum ether: EtOAc=1:2). The mixture was quenched with _D2O (3 mL), diluted with DCM (20 mL) and water (10 mL). The mixture was extracted with DCM (10 mL x 3). The combined organic layers were dried _{over Na2SO4} and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (12 g SepaFlash® silica flash column, Eluent of 50% EtOAc/Petroleum ether gradient @ 100 mL/min) to give the title compound (1.32 g, 5.61 mmol, 94.74% yield) as a yellow solid.

Step 6. Synthesis of (R)-3-(4-aminophenyl)piperidine-2,6-dione-3-d & (S)-3-(4-aminophenyl)piperidine-2,6-dione-3-d (9a&9b)

To a solution of 3-(4-nitrophenyl)piperidine-2,6-dione-3-d (1.05 g, 4.46 mmol) and NH ₄ Cl (716.36 mg, 13.39 mmol) in i-PrOH (30 mL) and H ₂ O (5 mL) was added Fe (747.88 mg, 13.39 mmol) under N ₂ . The mixture was stirred at 20 °C for 14 h. The peaks of the target mass and starting material were confirmed by LCMS. Additionally, Fe (249.29 mg, 4.46 mmol) and NH ₄ Cl (238.79 mg, 4.46 mmol) were added, and the mixture was further stirred at 20 °C for 2 h. The peaks of the target mass were confirmed by LCMS. The mixture was filtered, and the filter cake was washed with THF (100 mL). The filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (12 g SepaFlash® silica flash column, Eluent of 60% EtOAc/Petroleum ether gradient @ 200 mL/min) followed by prep-HPLC (Column: Waters Xbridge Prep OBD C18 150*40 mm*10um; Mobile phase: [H ₂ O (10 mM NH ₄ HCO ₃ ) - ACN]; Gradient: 0%-25% B over 15.0 min). The eluate was lyophilized to give 3-(4-aminophenyl)piperidine-2,6-dione-3-d (0.6 g, 2.63 mmol, 58.94% yield, 90% purity) as a white solid. The product (0.3 g) was separated by prep-SFC (column: DAICEL CHIRALPAK AS (250 mm*30 mm, 10 um); mobile phase: [CO ₂ -IPA]; B%: 45%, isocratic elution mode) to obtain two peaks. Peak 1 was concentrated under reduced pressure (<30 °C) to obtain product A, and peak 2 was concentrated under reduced pressure (<35 °C) to obtain product B. Product A was purified by prep-HPLC (column: Waters Xbridge C18 150*25mm*5um; mobile phase: [H ₂ O (10mM NH ₄ HCO ₃ ) - ACN]; gradient: 1%-15% B over 15.0 min), and the eluate was lyophilized to obtain (R)-3-(4-aminophenyl)piperidine-2,6-dione-3-d (0.1 g, 467.77 μmol, 10.48% yield, 96% purity) as a white solid. Product B was purified by prep-HPLC (column: Waters Xbridge C18 150*25mm*5um; mobile phase: [H ₂ O (10mM NH ₄ HCO ₃ ) - ACN]; gradient: 1%-15% B over 15.0 min), and the eluate was lyophilized to obtain (S)-3-(4-aminophenyl)piperidine-2,6-dione-3-d (90 mg, 420.99 μmol, 9.43% yield, 96% purity) as a white solid. MS(M+H) ⁺ =206.1

Step 7. Synthesis of benzyl ((1R,4r)-4-(4-(((4-((R)-2,6-dioxopiperidin-3-yl-3-d)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)carbamate (11)

To a solution of (R)-3-(4-aminophenyl)piperidine-2,6-dione-3-d (50 mg, 243.63 μmol) and benzyl ((1r,4r)-4-(4-formylpiperidin-1-yl)cyclohexyl)carbamate (55 mg, 159.68 μmol) in DCM (2 mL) and DMF (0.5 mL) was added deuterated acetic acid (29 mg, 482.93 μmol), and the mixture was stirred at 20 °C for 0.5 h. Then, NaBH(OAc) ₃ (154.9 mg, 730.87 μmol) was added, and the mixture was stirred at 20 °C for 0.5 h. The peak of the target mass was confirmed by LCMS. The mixture was concentrated under reduced pressure. The product was purified by prep-HPLC (column: Phenomenex Luna C18 150*25 mm*10um; mobile phase: [H ₂ O (0.1% TFA) - ACN]; gradient: 3%-33% B over 15.0 min). The eluate was lyophilized to obtain the title compound as a yellow solid (63 mg, 97.27 μmol, 60.92% yield, TFA salt).

Step 8. Synthesis of (R)-3-(4-(((1-((1r,4R)-4-aminocyclohexyl)piperidin-4-yl)methyl)amino)phenyl)piperidine-2,6-dione-3-d (12)

A solution of benzyl ((1R,4r)-4-(4-(((4-((R)-2,6-dioxopiperidin-3-yl-3-d)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)carbamate (60 mg, 92.64 μmol, TFA salt) in TFA (5 mL) was stirred at 50 °C for 2 h. The peak of the desired mass was identified by LCMS. The mixture was concentrated under reduced pressure to obtain the title compound (45 mg, crude, TFA salt) as a yellow oil.

Step 9. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1R,4R)-4-(4-(((4-((R)-2,6-dioxopiperidin-3-yl-3-d)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 20)

To a solution of (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoic acid (25 mg, 60.76 μmol) and HATU (27.72 mg, 72.91 μmol) in DMF (0.5 mL) was added DIPEA (82.32 mg, 636.98 μmol, 110.95 μL), and the mixture was stirred at 20 °C for 15 min. After that, (R)-3-(4-(((1-((1r,4R)-4-aminocyclohexyl)piperidin-4-yl)methyl)amino)phenyl)piperidine-2,6-dione-3-d (45 mg, 87.62 μmol, TFA salt) was added at 0 °C, and the mixture was stirred at 0 °C for 30 min. The peak of the target mass was identified by LCMS. The mixture was filtered, and the filter cake was washed with DMF (0.2 mL). The filtrate was purified by prep-HPLC (column: Waters Xbridge C18 150*25 mm*5um; mobile phase: [H ₂ O (10 mM NH ₄ HCO ₃ ) - ACN]; gradient: 33% - 63% B over 15.0 min), and the eluate was lyophilized to obtain product A (20.7 mg, 89% purity). Product A (5.2 mg) was delivered. The residue (14.5 mg) was purified by prep-HPLC (column: Phenomenex Luna C18 150*25mm*10um; mobile phase: [H ₂ O (0.225% FA) - ACN]; gradient: 8%-38% B over 10.0 min), and the eluate was lyophilized. The product was diluted with DCM (10 mL) and deionized water (10 mL), and the pH was adjusted to 8 with saturated NaHCO _{3 .} The mixture was extracted with DCM (30 mL x 2). The combined organic layer was washed with deionized water (10 mL), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure. The product was diluted with ACN (2 mL) and deionized water (15 mL), and then lyophilized to obtain the title compound as a white solid (2.1 mg, 2.52 μmol, 4.14% yield, 95% purity). MS(M+H) ⁺ = 793.6

^1H NMR (400 MHz, DMSO-d ₆ ) δ = 10.74 (s, 1H), 8.41 (d, J = 8.9 Hz, 1H), 8.03 (br d, J = 7.8 Hz, 1H), 7.89 (s, 1H), 7.62 (s, 1H), 7.51 - 7.43 (m, 2H), 6.88 (d, J = 8.6 Hz, 2H), 6.50 (d, J = 8.4 Hz, 2H), 5.62 - 5.53 (m, 1H), 4.48 - 4.38 (m, 1H), 4.36 - 4.27 (m, 1H), 3.93 (s, 3H), 3.77 - 3.66 (m, 1H), 3.23 (s, 3H), 2.91 - 2.78 (m, 4H), 2.63 - 2.56 (m, 1H), 2.47 - 2.39 (m, 1H), 2.31 - 2.24 (m, 1H), 2.23 - 2.12 (m, 2H), 2.08 - 1.85 (m, 6H), 1.84 - 1.67 (m, 8H), 1.65 - 1.54 (m, 2H), 1.52 - 1.42 (m, 1H), 1.41 - 1.30 (m, 4H), 1.27 - 1.20 (m, 3H), 1.17 - 1.08 (m, 2H)

Example 21. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)-3-hydroxyphenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 21)

Step 1. Synthesis of tert-butyl ((1r,4r)-4-(4-benzylpiperazin-1-yl)cyclohexyl)carbamate (3)

A solution of 2-bromo-5-nitrophenol (1.60 g, 7.34 mmol), 2,6-bis(benzyloxy)-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)pyridine (3.68 g, 8.81 mmol), K ₃ PO ₄ (1.5 M, 14.7 mL), and APhos Pd G3 (466.1 mg, 733.93 μmol) in toluene (20 mL) was degassed and purged three times with N ₂ , and the mixture was stirred at 60 °C under N ₂ for 16 h. The peak of the target mass (57%) was identified by LCMS. The mixture was filtered, the filtrate was diluted with water (50 mL), extracted with EtOAc (150 mL x 3), the combined organic layers were washed with brine (50 mL x 3), dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure to obtain a residue. The residue was purified by flash silica gel chromatography (80 g SepaFlash® silica flash column, Eluent of 0–10% EtOAc/Petroleum ether gradient @ 40 mL/min) to give the title compound (2.80 g, 6.47 mmol, 88.16% yield, 99% purity) as a yellow oil. MS(M+H) ⁺ = 429.2.

Step 2. Synthesis of tert-butyl (4-(2,6-dioxopiperidin-3-yl)-3-hydroxyphenyl)carbamate (4)

To a solution of 2-(2,6-bis(benzyloxy)pyridin-3-yl)-5-nitrophenol (1.40 g, 3.24 mmol) and Boc ₂ O (2.12 g, 9.71 mmol) in MeOH (15 mL) and THF (30 mL) was added Pd(OH) ₂ (400.00 mg, 10% purity) under N ₂ . The suspension was degassed and purged three times with H ₂ . The mixture was stirred at 25 °C under CH ₂ (50 Psi) for 48 h. The desired mass peak (82%) was identified by LCMS. The mixture was filtered, and the filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (20 g SepaFlash® silica flash column, eluent of 10–20% MeOH/EtOAc @ 40 mL/min) to give the title compound (600 mg, 1.84 mmol, 56.74% yield, 98% purity) as an off-white solid. MS(M+H) ⁺ = 321.2.

¹ H NMR (400 MHz, DMSO-d ₆ ) δ = 10.66 (s, 1H), 9.48 (s, 1H), 9.19 (s, 1H), 7.11 (s, 1H), 6.87 (d, J = 8.0 Hz, 1H), 6.75 (dd, J = 8.4, 2.0 Hz, 1H), 3.82 - 3.69 (m, 1H), 2.67 - 2.59 (m, 1H), 2.48 - 2.41 (m, 1H), 2.27 - 2.12 (m, 1H), 1.92 - 1.81 (m, 1H), 1.46 (s, 9H).

Step 3. Synthesis of 3-(4-amino-2-hydroxyphenyl)piperidine-2,6-dione (5)

To a solution of tert-butyl (4-(2,6-dioxopiperidin-3-yl)-3-hydroxyphenyl)carbamate (600 mg, 1.84 mmol) in DCM (5 mL) was added HCl/dioxane (2 M, 20 mL). The mixture was stirred at 20 °C for 30 h. The target mass peak (93%) was identified by LCMS. The mixture was concentrated under reduced pressure to give the title compound (570 mg, crude, HCl) as an off-white solid. MS (M+H) ⁺ = 221.1.

Step 4. Synthesis of benzyl ((1r,4r)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)-3-hydroxyphenyl)amino)methyl)piperidin-1-yl)cyclohexyl)carbamate (7)

To a solution of 3-(4-amino-2-hydroxyphenyl)piperidine-2,6-dione (550 mg, 1.99 mmol, HCl) and benzyl ((1r,4r)-4-(4-formylpiperidin-1-yl)cyclohexyl)carbamate (549 mg, 1.59 mmol) in DCM (20 mL) and DMF (5 mL) was added NaOAc (490 mg, 5.98 mmol). The mixture was stirred at 20 °C for 1 h. Then, NaBH(OAc) ₃ (1.06 g, 4.98 mmol) was added, and the mixture was stirred at 20 °C for 14 h. The desired mass peak (94%) was confirmed by LCMS. The reaction mixture was diluted with water (20 mL), adjusted to pH=9 with saturated NaHCO ₃ , and extracted with DCM (50 mL X 3 ). The combined organic layers were washed with brine (20 mL X 3 ), dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (10 g SepaFlash® silica flash column, eluent of 30–40% MeOH/EtOAc @ 40 mL/min) to give the title compound (180 mg, 324.78 μmol, 16.30% yield, 99% purity) as an off-white solid. MS(M+H) ⁺ = 549.3.

Step 5. Synthesis of 3-(4-(((1-((1r,4r)-4-aminocyclohexyl)piperidin-4-yl)methyl)amino)-2-hydroxyphenyl)piperidine-2,6-dione (8)

A solution of benzyl ((1r,4r)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)-3-hydroxyphenyl)amino)methyl)piperidin-1-yl)cyclohexyl)carbamate (180 mg, 324.78 μmol) in TFA (3 mL) was stirred at 30 °C under CN ₂ for 16 h. The main peak of the desired mass was identified by LCMS. The mixture was concentrated under reduced pressure to give the title compound (171 mg, 323.52 μmol, 99.61% yield, TFA) as a brown oil. MS(M+H) ⁺ = 415.2.

Step 6. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)-3-hydroxyphenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 21)

The title compound (110.41 mg, 124.78 μmol, 38.57% yield, 92.9% purity) was obtained as a yellowish-white solid by a similar method to step 2 of Example 1. MS(M+H) ⁺ =822.5.

¹ H NMR (400 MHz, DMSO-d ₆ ) δ = 10.60 (s, 1H), 9.03 (s, 1H), 8.45 - 8.35 (m, 1H), 8.07 - 7.97 (m, 1H), 7.84 (s, 1H), 7.59 (s, 1H), 7.51 - 7.41 (m, 2H), 6.67 (d, J = 8.4 Hz, 1H), 6.06 - 6.02 (m, 1H), 6.00 - 5.95 (m, 1H), 5.53 - 5.43 (m, 1H), 4.42 - 4.30 (m, 1H), 4.28 - 4.19 (m, 1H), 3.93 (s, 3H), 3.78 - 3.68 (m, 1H), 3.68 - 3.61 (m, 1H), 3.24 (s, 3H), 2.92 - 2.73 (m, 4H), 2.64 - 2.53 (m, 1H), 2.46 - 2.38 (m, 1H), 2.30 - 2.22 (m, 1H), 2.20 - 2.06 (m, 3H), 2.06 - 1.97 (m, 1H), 1.94 - 1.85 (m, 4H), 1.85 - 1.70 (m, 9H), 1.67 - 1.58 (m, 3H), 1.54 - 1.43 (m, 1H), 1.42 - 1.28 (m, 4H), 1.20 - 1.06 (m, 2H), 0.76 (t, J = 7.6 Hz, 3H).

Example 22. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((6-(2,6-dioxopiperidin-3-yl)pyridin-3-yl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 22)

Step 1. Synthesis of tert-butyl (2',6'-bis(benzyloxy)-[2,3'-bipyridin]-5-yl)carbamate (3)

The title compound (7.17 g, 14.68 mmol, 61.26% yield, 99% purity) was obtained as a yellow solid by a similar method to step 1 of Example 21. MS(M+H) ⁺ = 484.2.

Step 2. Synthesis of tert-butyl (6-(2,6-dioxopiperidin-3-yl)pyridin-3-yl)carbamate (4)

A solution of Pd(OH) ₂ /C (2 g, 20% purity) in THF (100 mL) was slowly added to a solution of tert-butyl (2',6'-bis(benzyloxy)-[2,3'-bipyridin]-5-yl)carbamate (6.67 g, 13.79 mmol) in MeOH (30 mL) and THF (200 mL) under N ₂ , and the mixture was stirred at 25 °C under CH ₂ (45 Psi) for 24 h. The mixture was filtered, and the filter cake was washed with THF (600 mL). The filtrate was concentrated under reduced pressure to give the title compound (3.84 g, crude) as a green solid. MS(M+H) ⁺ = 306.2.

Step 3. Synthesis of 3-(5-aminopyridin-2-yl)piperidine-2,6-dione (5)

To a solution of tert-butyl (6-(2,6-dioxopiperidin-3-yl)pyridin-3-yl)carbamate (3.84 g, 12.58 mmol) in DCM (50 mL) was added HCl/dioxane (2 M, 100 mL), and the mixture was stirred at 25 °C for 20 h. LCMS confirmed that the starting material remained. HCl/dioxane (2 M, 100 mL) and DMF (6 mL) were added, and the mixture was stirred at 35 °C for 2 h. LCMS confirmed that the starting material was consumed. The mixture was concentrated under reduced pressure. The product was diluted with water (50 mL) at 0 °C, and the pH was adjusted to 9 with saturated Na ₂ CO ₃ . The mixture was washed with EtOAc (20 mL x 3), the aqueous phase was lyophilized, diluted with DCM/MeOH=10/1 (200 mL), and the suspension was stirred at 25 °C for 1 h. The mixture was filtered, and the filter cake was washed with DCM/MeOH=10/1 (30 mL). The filtrate was concentrated under reduced pressure to obtain the title compound (1.6 g, crude) as a yellow solid.

Step 4. Synthesis of benzyl ((1r,4r)-4-(4-(((6-(2,6-dioxopiperidin-3-yl)pyridin-3-yl)amino)methyl)piperidin-1-yl)cyclohexyl)carbamate (7)

To a solution of 3-(5-aminopyridin-2-yl)piperidine-2,6-dione (357 mg, 1.74 mmol) in DCM (10 mL) and DMF (10 mL) was added AcOH (87.00 mg, 1.45 mmol, 82.94 μL), followed by benzyl ((1r,4r)-4-(4-formylpiperidin-1-yl)cyclohexyl)carbamate (0.5 g, 1.45 mmol), and the resulting mixture was stirred at 25 °C for 30 min. Then, NaBH(OAc) ₃ (921.19 mg, 4.35 mmol) was added, and the mixture was stirred at 25 °C for 30 min. The peak of the desired mass was confirmed by LCMS. The mixture was quenched with saturated NaHCO ₃ (20 mL) at 0 °C, then extracted with EtOAc (10 mL x 3). The combined organic layers were washed with water (10 mL), dried over Na ₂ SO _{4 ,} and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (5 g SepaFlash® silica flash column, eluent of 10–20% MeOH/EtOAc gradient @ 50 mL/min) to give the title compound (380 mg, 690.70 μmol, 47.67% yield, 97% purity) as a yellow solid. MS(M+H) ⁺ = 534.4.

Step 5. Synthesis of 3-(5-(((1-((1r,4r)-4-aminocyclohexyl)piperidin-4-yl)methyl)amino)pyridin-2-yl)piperidine-2,6-dione (8)

The title compound (370 mg, crude, TFA salt) as a yellow oil was obtained by a similar method to step 5 of Example 21. MS(M+H) ⁺ = 400.3.

Step 6. 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((6-(2,6-dioxopiperidin-3-yl)pyridin-3-yl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 22)

Synthesized in a similar manner to step 6 of Example 21, the title compound as a yellow solid (110.6 mg, 91.44 μmol, 11.79% yield, 95% purity, 3TFA salt) and the title compound as a white solid (59.7 mg, 47.80 μmol, 6.16% yield, 92% purity, 3TFA salt) were obtained. MS(M+H) ⁺ =807.6

^1H NMR (400 MHz, DMSO-d ₆ ) δ = 10.96 (br s, 1H), 9.26 - 8.92 (m, 2H), 8.26 (br d, J = 7.8 Hz, 1H), 8.03 - 7.90 (m, 2H), 7.77 (s, 1H), 7.56 - 7.49 (m, 2H), 7.43 - 7.33 (m, 2H), 4.46 - 4.41 (m, 1H), 4.23 - 4.15 (m, 1H), 4.08 - 4.00 (m, 1H), 3.91 (s, 3H), 3.84 - 3.76 (m, 1H), 3.54 - 3.46 (m, 2H), 3.29 - 3.13 (m, 4H), 3.07 - 2.95 (m, 4H), 2.69 - 2.57 (m, 1H), 2.30 - 2.20 (m, 1H), 2.15 - 1.73 (m, 15H), 1.68 - 1.36 (m, 10H), 0.75 (t, J = 7.5 Hz, 3H)

Example 23. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((4-(2,4-dioxotetrahydropyrimidin-1(2H)-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 23)

Step 1. Synthesis of tert-butyl (4-(2,4-dioxotetrahydropyrimidin-1(2H)-yl)phenyl)carbamate (2)

To a solution of 1-(4-bromophenyl)dihydropyrimidine-2,4(1H,3H)-dione (500 mg, 1.86 mmol) and tert-butyl carbamate (326.50 mg, 2.79 mmol) in dioxane (10 mL) were added Xphos Pd G ₄ (159.88 mg, 185.81 μmol) and t-BuONa (357.14 mg, 3.72 mmol), and the mixture was stirred at 100 °C for 14 h. The major peak of the desired mass was identified by LCMS. The mixture was diluted with H ₂ O (20 mL) and extracted with EtOAc (10 mL x 3). The combined organic layers were washed with brine (20 mL), dried over Na ₂ SO ₄ , filtered, and the filtrate was concentrated under reduced pressure. The residue was triturated with MTBE (20 mL), filtered, and the filter cake was collected to obtain the title compound (300 mg, 982.55 μmol, 52.88% yield) as a yellow solid. MS (Mt-Bu+H) ⁺ = 250.2

Step 2. Synthesis of 1-(4-aminophenyl)dihydropyrimidine-2,4(1H,3H)-dione (3)

A solution of tert-butyl (4-(2,4-dioxotetrahydropyrimidin-1(2H)-yl)phenyl)carbamate (150 mg, 491.27 μmol) in HCl/dioxane (2 M, 2 mL) was stirred at 20 °C for 1 h. The main peak of the desired mass was identified by LCMS. The mixture was concentrated under reduced pressure to obtain the title compound (120 mg, crude, HCl) as a yellow solid. MS (M+H) ⁺ = 206.0

Step 3. Synthesis of benzyl ((1r,4r)-4-(4-(((4-(2,4-dioxotetrahydropyrimidin-1(2H)-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)carbamate (5)

To a solution of 1-(4-aminophenyl)dihydropyrimidine-2,4(1H,3H)-dione (120 mg, 496.54 μmol, HCl) and benzyl ((1r,4r)-4-(4-formylpiperidin-1-yl)cyclohexyl)carbamate (130 mg, 377.42 μmol) in DMF (2 mL) and DCM (2 mL) was added NaOAc (203.65 mg, 2.48 mmol), and the mixture was stirred at 20 °C for 1 h. NaBH(OAc) ₃ (157.85 mg, 744.81 μmol) was added, and the mixture was stirred at 20 °C for 2 h. The target mass peak (72%) was identified by LCMS. The mixture was diluted with H ₂ O (20 mL) and extracted with EtOAc (10 mL x 3). The mixed organic layer was washed with brine (20 mL), dried over Na ₂ SO ₄ , filtered, and the filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (5 g SepaFlash® silica flash column, eluent of 0–100% EtOAc/Commercial hexanes gradient @ 100 mL/min) to give the title compound (45 mg, 84.32 μmol, 16.98% yield) as a yellow solid. MS (M+H) ⁺ = 534.2

Step 4. Synthesis of 1-(4-(((1-((1r,4r)-4-aminocyclohexyl)piperidin-4-yl)methyl)amino)phenyl)dihydropyrimidine-2,4(1H,3H)-dione (6)

A mixture of benzyl ((1r,4r)-4-(4-(((4-(2,4-dioxotetrahydropyrimidin-1(2H)-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)carbamate (45 mg, 84.32 μmol) in TFA (1.54 g, 13.46 mmol, 1 mL) was stirred at 40 °C for 1 h. The main peak of the desired mass was identified by LCMS, and the mixture was concentrated under reduced pressure to obtain the title compound (45 mg, crude, TFA) as a yellow oil. MS (M+H) ⁺ = 400.4

Step 5. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((4-(2,4-dioxotetrahydropyrimidin-1(2H)-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 23)

The title compound (20.8 mg, 24.92 μmol, 28.44% yield, 95% purity) was obtained as a white solid by a similar method to step 2 of Example 1. MS(M+H) ⁺ = 793.5

^1H NMR (400 MHz, DMSO-d ₆ ) δ = 10.23 (s, 1H), 8.44 (d, J = 8.9 Hz, 1H), 8.13 - 8.05 (m, 1H), 7.92 (s, 1H), 7.65 (s, 1H), 7.53 - 7.45 (m, 2H), 7.00 (d, J = 8.6 Hz, 2H), 6.57 (d, J = 8.7 Hz, 2H), 5.85 - 5.69 (m, 1H), 4.49 - 4.40 (m, 1H), 4.34 (q, J = 6.5 Hz, 1H), 3.96 (s, 3H), 3.81 - 3.70 (m, 1H), 3.66 (t, J = 6.7 Hz, 2H), 3.25 (s, 3H), 2.92 (s, 3H), 2.68 (t, J = 6.7 Hz, 2H), 2.37 - 2.16 (m, 2H), 2.08 - 1.98 (m, 2H), 1.93 (s, 3H), 1.87 - 1.71 (m, 8H), 1.69 - 1.61 (m, 3H), 1.48 - 1.35 (m, 4H), 1.30 - 1.11 (m, 6H).

Example 24 Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((4-((2,6-dioxopiperidin-3-yl)oxy)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 24)

Step 1. Synthesis of tert-butyl (4-((2,6-dioxopiperidin-3-yl)oxy)phenyl)carbamate (3)

To a solution of tert-butyl (4-hydroxyphenyl)carbamate (1 g, 4.78 mmol) in DMF (10 mL) was added NaH (477.87 mg, 11.95 mmol, 60% purity), and the resulting mixture was stirred at 20 °C for 1 h. 3-Bromopiperidine-2,6-dione (1.38 g, 7.17 mmol, 1.5 eq) was added, and the resulting mixture was stirred at 20 °C for 1 h. After confirming the complete consumption of tert-butyl (4-hydroxyphenyl)carbamate by LCMS, the mixture was slowly poured into ice-water (50 mL) under N ₂ and extracted with EtOAc (30 mL x 3). The mixed organic layer was washed with brine (50 mL), dried over anhydrous Na ₂ SO ₄ , filtered, and concentrated under reduced pressure to obtain the title compound (1.4 g, 4.37 mmol, 91.45% yield) as a yellow solid. MS (Mt-Bu+H) ⁺ = 264.9

Step 2. Synthesis of 3-(4-aminophenoxy)piperidine-2,6-dione (4)

A mixture of tert-butyl (4-((2,6-dioxopiperidin-3-yl)oxy)phenyl)carbamate (500 mg, 1.56 mmol) in HCl/dioxane (2 M, 10 mL) was stirred at 20 °C for 2 h. The main peak of the desired mass was identified by LCMS. The mixture was concentrated under reduced pressure to obtain the title compound (0.4 g, 1.56 mmol, 99.84% yield, HCl) as a white solid. MS (M+H) ⁺ = 221.0

Step 3. Synthesis of benzyl ((1r,4r)-4-(4-(((4-((2,6-dioxopiperidin-3-yl)oxy)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)carbamate (6)

To a solution of 3-(4-aminophenoxy)piperidine-2,6-dione (0.2 g, 779.17 μmol, HCl salt) and benzyl ((1r,4r)-4-(4-formylpiperidin-1-yl)cyclohexyl)carbamate (200 mg, 580.64 μmol) in DCM (2 mL) and DMF (2 mL) were added NaOAc (95.88 mg, 1.17 mmol) and NaBH(OAc) ₃ (330.27 mg, 1.56 mmol), and the resulting mixture was stirred at 20 °C for 14 h. The major peak of the desired mass was identified by LCMS. The mixture was diluted with water (20 mL), extracted with DCM (20 mL x 3), and the combined organic layers were washed with brine (50 mL), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (5 g SepaFlash® silica flash column, eluent of 0–100% EtOAc/Petroleum ether gradient @ 80 mL/min) to give the title compound (100 mg, 182.26 μmol, 23.39% yield, 100% purity) as a yellow solid. MS (M+H) ⁺ = 549.3

Step 4. Synthesis of 3-(4-(((1-((1r,4r)-4-aminocyclohexyl)piperidin-4-yl)methyl)amino)phenoxy)piperidine-2,6-dione (7)

A solution of benzyl ((1r,4r)-4-(4-(((4-((2,6-dioxopiperidin-3-yl)oxy)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)carbamate (100 mg, 182.26 μmol) in TFA (3 mL) was stirred at 50 °C for 2 h. The main peak of the desired mass was identified by LCMS. The mixture was concentrated under reduced pressure to obtain the title compound (0.1 g, crude, TFA) as a yellow oil. MS (M+H) ⁺ = 415.2

Step 5. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((4-((2,6-dioxopiperidin-3-yl)oxy)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 24)

To a solution of (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoic acid (75 mg, 182.28 μmol) in DMF (3 mL) were added DIPEA (70.42 mg, 544.87 μmol, 94.91 μL) and HATU (80 mg, 210.40 μmol), and the mixture was stirred at 20 °C for 1 h. 3-(4-(((1-((1r,4r)-4-aminocyclohexyl)piperidin-4-yl)methyl)amino)phenoxy)piperidine-2,6-dione (96 mg, 181.62 μmol, TFA salt) was added, and the mixture was stirred at 20 °C for 14 h. The target mass peak (68%) was identified by LCMS. The mixture was diluted with H ₂ O (20 mL) and extracted with EtOAc (10 mL x 3). The combined organic layers were washed with brine (20 mL), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by prep-HPLC (column: Phenomenex Luna C18 150 * 25 mm * 10 um; mobile phase: [H ₂ O (0.1% TFA)-ACN]; gradient: 0%-25% B over 15.0 min). The target product was dissolved in H ₂ O (20 mL), adjusted to pH = 8-9 with NaHCO ₃ , and the resulting suspension was extracted with EtOAc (10 mL x 3). The combined organic layers were dried over Na ₂ SO ₄ and filtered. The filtrate was concentrated under reduced pressure, and the residue was lyophilized to obtain the title compound as a white solid (43.6 mg, 51.80 μmol, 28.52% yield, 96% purity). MS(M+H) ⁺ =808.4

^1H NMR (400 MHz, DMSO-d ₆ ) δ = 10.86 (s, 1H), 8.43 (d, J = 8.9 Hz, 1H), 8.04 (d, J = 8.3 Hz, 1H), 7.91 (s, 1H), 7.63 (s, 1H), 7.52 - 7.45 (m, 2H), 6.80 (d, J = 8.9 Hz, 2H), 6.50 (d, J = 8.8 Hz, 2H), 5.27 (t, J = 5.7 Hz, 1H), 4.85 (dd, J = 4.8, 10.1 Hz, 1H), 4.52 - 4.40 (m, 1H), 4.34 (q, J = 6.7 Hz, 1H), 3.95 (s, 3H), 3.80 - 3.64 (m, 1H), 3.25 (s, 3H), 2.93 - 2.80 (m, 4H), 2.67 - 2.58 (m, 1H), 2.33 - 2.25 (m, 1H), 2.22 - 2.12 (m, 3H), 2.10 - 2.00 (m, 2H), 1.96 - 1.89 (m, 3H), 1.85 - 1.71 (m, 9H), 1.67 - 1.60 (m, 2H), 1.53 - 1.45 (m, 1H), 1.42 - 1.32 (m, 4H), 1.27 - 1.21 (m, 3H), 1.20 - 1.12 (m, 2H).

Example 25. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((4-((2,6-dioxopiperidin-3-yl)amino)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 25)

Step 1. Synthesis of tert-butyl (4-((2,6-dioxopiperidin-3-yl)amino)phenyl)carbamate (3)

To a solution of tert-butyl (4-aminophenyl)carbamate (3 g, 14.41 mmol) in ACN (20 mL) were added 3-bromopiperidine-2,6-dione (5.53 g, 28.81 mmol), TBAI (200 mg, 541.47 μmol), and NaHCO ₃ (6.05 g, 72.03 mmol) at 20 °C, and the mixture was stirred at 80 °C for 16 h. The peak of the desired mass was identified by LCMS. The reaction mixture was filtered. The filter cake was washed with EtOAc (100 mL), and the filtrate was concentrated under reduced pressure. The product was triturated with a mixed solvent (EtOAc: MTBE = 1:2; 60 mL) at 20 °C for 1 h. The mixture was filtered. The filter cake was dried under reduced pressure to obtain the title compound as a green solid (2.8 g, 8.77 mmol, 60.86% yield). MS(M+ H) ⁺ = 320.2

¹ H NMR (400 MHz, DMSO-d ₆ ) δ = 10.78 (s, 1H), 8.93 - 8.76 (m, 1H), 7.24 - 7.06 (m, 2H), 6.60 (d, J = 8.9 Hz, 2H), 5.85 - 5.22 (m, 1H), 4.32 - 4.18 (m, 1H), 2.78 - 2.64 (m, 1H), 2.63 - 2.55 (m, 1H), 2.15 - 2.04 (m, 1H), 1.93 - 1.74 (m, 1H), 1.45 (s, 9H)

Step 2. Synthesis of 3-((4-aminophenyl)amino)piperidine-2,6-dione (4)

The title compound (360 mg, crude, HCl) was obtained as a green solid by a similar method to step 2 of Example 24. MS (M+H) ⁺ = 220.1

^1H NMR (400 MHz, DMSO-d ₆ ) δ = 10.82 (s, 1H), 10.05 - 9.89 (m, 2H), 7.11 (d, J = 8.8 Hz, 2H), 6.74 (d, J = 8.8 Hz, 2H), 5.17 (br s, 2H), 4.45 - 4.28 (m, 1H), 2.80 - 2.69 (m, 1H), 2.63 - 2.55 (m, 1H), 2.17 - 2.01 (m, 1H), 1.97 - 1.83 (m, 1H)

Synthesis of benzyl ((1r,4r)-4-(4-(((4-((2,6-dioxopiperidin-3-yl)amino)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)carbamate (6)

The title compound (170 mg, 310.40 μmol, 39.68% yield) was obtained as a green solid by a similar method to step 3 of Example 24. MS (M+H) ⁺ = 548.4

Step 4. Synthesis of 3-((4-(((1-((1r,4r)-4-aminocyclohexyl)piperidin-4-yl)methyl)amino)phenyl)amino)piperidine-2,6-dione (7)

The title compound (105 mg, crude, TFA) as a green oil was obtained by a similar method to step 4 of Example 24. MS (M+H) ⁺ = 414.3

Step 5. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((4-((2,6-dioxopiperidin-3-yl)amino)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 25)

The title compound (24.7 mg, 28.16 μmol, 14.48% yield, 92% purity) was obtained as a pale yellow solid by a similar method to step 5 of Example 24. MS (M+H) ⁺ = 807.5

¹ H NMR (400 MHz, DMSO-d ₆ ) δ 10.74 (br s, 1H), 8.45 - 8.37 (m, 1H), 8.07 - 7.97 (m, 1H), 7.90 (s, 1H), 7.62 (s, 1H), 7.50 - 7.43 (m, 2H), 6.57 - 6.51 (m, 2H), 6.46 - 6.39 (m, 2H), 5.02 - 4.94 (m, 1H), 4.83 - 4.75 (m, 1H), 4.48 - 4.38 (m, 1H), 4.36 - 4.28 (m, 1H), 4.11 - 4.02 (m, 1H), 3.94 (s, 3H), 3.77 - 3.65 (m, 1H), 3.24 (s, 3H), 2.85 - 2.76 (m, 3H), 2.74 - 2.65 (m, 1H), 2.61 - 2.54 (m, 1H), 2.46 - 2.40 (m, 1H), 2.30 - 2.24 (m, 1H), 2.22 - 2.08 (m, 3H), 2.05 - 1.99 (m, 1H), 1.94 - 1.86 (m, 3H), 1.84 - 1.71 (m, 9H), 1.65 - 1.58 (m, 2H), 1.42 - 1.26 (m, 5H), 1.24 - 1.21 (m, 3H), 1.18 - 1.08 (m, 2H)

Example 26. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((4-((2,6-dioxopiperidin-3-yl)amino)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-(2-hydroxyethoxy)benzamide (Compound 26)

Step 1. Synthesis of benzyl ((1r,4r)-4-(4-(((4-((2,6-dioxopiperidin-3-yl)amino)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)carbamate (3)

To a solution of 3-(4-aminoanilino)piperidine-2,6-dione (300 mg, 1.17 mmol, HCl) and benzyl ((1r,4r)-4-(4-formylpiperidin-1-yl)cyclohexyl)carbamate (404.12 mg, 1.17 mmol) in DMF (5 mL) were added NaOAc (481.23 mg, 5.87 mmol) and NaBH(OAc) ₃ (372.99 mg, 1.76 mmol), and the mixture was stirred at 20 °C for 14 h. The major peak of the desired mass was identified by LCMS. The mixture was diluted with water (20 mL) and extracted with DCM (20 mL x 3). The combined organic layers were washed with brine (50 mL), dried over Na ₂ SO ₄ , filtered, and the filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (10 g SepaFlash® silica flash column, eluent of 0–100% EtOAc/Petroleum ether gradient @ 80 mL/min) to give the title compound (200 mg, 365.17 μmol, 31.12% yield) as a yellow solid. MS(M+H) ⁺ = 548.4

Step 2. Synthesis of 3-((4-(((1-((1r,4r)-4-aminocyclohexyl)piperidin-4-yl)methyl)amino)phenyl)amino)piperidine-2,6-dione (4)

The title compound (100 mg, crude, TFA) was obtained as a yellow oil by a similar method to step 4 of Example 24. MS (M+H) ⁺ = 414.4

Step 3. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((4-((2,6-dioxopiperidin-3-yl)amino)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-(2-hydroxyethoxy)benzamide (Compound 26)

The title compound (2.7 mg, 3.03 μmol, 1.60% yield, 94% purity) was obtained as a brown solid by a similar method to step 5 of Example 24. MS(M+H) ⁺ = 837.5

^1H NMR (400 MHz, DMSO-d ₆ ) δ = 10.77 (s, 1H), 8.43 (d, J = 9.0 Hz, 1H), 8.07 (s, 1H), 8.03 (d, J = 8.0 Hz, 1H), 7.91 (s, 1H), 7.49 - 7.44 (m, 2H), 6.54 (d, J = 8.6 Hz, 2H), 6.43 (d, J = 8.8 Hz, 2H), 5.20 (t, J = 5.9 Hz, 1H), 5.00 (d, J = 7.3 Hz, 1H), 4.50 - 4.38 (m, 1H), 4.33 (q, J = 6.3 Hz, 1H), 4.17 - 4.05 (m, 3H), 3.84 - 3.76 (m, 2H), 3.76 - 3.66 (m, 1H), 3.46 - 3.39 (m, 1H), 3.25 (s, 3H), 2.95 - 2.83 (m, 3H), 2.83 - 2.75 (m, 2H), 2.35 - 2.32 (m, 1H), 2.25 - 2.17 (m, 2H), 2.14 - 2.09 (m, 1H), 2.07 - 1.96 (m, 2H), 1.94 - 1.87 (m, 3H), 1.84 - 1.72 (m, 9H), 1.64 - 1.57 (m, 2H), 1.53 - 1.46 (m, 1H), 1.45 - 1.33 (m, 4H), 1.24 (d, J = 6.5 Hz, 3H), 1.19 - 1.11 (m, 2H).

Example 27. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((4-((2,6-dioxopiperidin-3-yl)(methyl)amino)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 27)

Step 1. Synthesis of tert-butyl (4-((2,6-dioxopiperidin-3-yl)(methyl)amino)phenyl)carbamate (2)

To a solution of tert-butyl (4-((2,6-dioxopiperidin-3-yl)amino)phenyl)carbamate (300 mg, 939.39 μmol) in DCM (5 mL) and MeOH (5 mL) were added HOAc (56.41 mg, 939.39 μmol, 53.78 μL) and HCHO (763.00 mg, 9.40 mmol, 700 μL). The mixture was stirred at 20 °C for 1 h. Then, NaBH ₃ CN (500 mg, 7.96 mmol) was added at 0 °C, and the mixture was stirred at 20 °C for 15 h. The target mass peak (82%) was confirmed by LCMS. H ₂ O (10 mL) was added to the reaction mixture, concentrated under reduced pressure to remove DCM and MeOH, diluted with EtOAc (30 mL), and adjusted to pH = 9 with NaHCO ₃ (sat. aq, 10 mL). The mixture was extracted with EtOAc (25 mL × 2), and the combined organic layer was washed with brine (20 mL × 2), dried over Na ₂ SO ₄ , filtered, and the filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (10 g SepaFlash® silica flash column, Eluent of 28–50% EtOAc/Petroleum ether gradient @ 100 mL/min) to give the title compound (200 mg, 599.91 μmol, 63.86% yield) as a pale green solid. MS (M+ H) ⁺ = 334.1

^1H NMR (400 MHz, DMSO-d ₆ ) δ = 10.77 (s, 1H), 9.01 - 8.85 (m, 1H), 7.33 - 7.15 (m, 2H), 6.73 (d, J = 9.2 Hz, 2H), 4.85 - 4.69 (m, 1H), 2.89 - 2.75 (m, 1H), 2.69 (s, 3H), 2.57 - 2.53 (m, 1H), 2.33 - 2.21 (m, 1H), 1.91 - 1.80 (m, 1H), 1.46 (s, 9H)

Step 2. Synthesis of 3-((4-aminophenyl)(methyl)amino)piperidine-2,6-dione (3)

To a solution of tert-butyl (4-((2,6-dioxopiperidin-3-yl)(methyl)amino)phenyl)carbamate (200 mg, 599.91 μmol) in dioxane (3 mL) was added HCl/dioxane (2 M, 5.75 mL). The mixture was stirred at 25 °C under CN ₂ for 48 h. The main peak of the desired mass was identified by LCMS. The reaction mixture was concentrated under reduced pressure to obtain the title compound (160 mg, crude, HCl) as a green solid. MS (M+H) ⁺ = 234.1

Step 3. Synthesis of benzyl ((1r,4r)-4-(4-(((4-((2,6-dioxopiperidin-3-yl)(methyl)amino)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)carbamate (5)

The title compound (160 mg, 284.84 μmol, 48.02% yield) was obtained as a green solid by a similar method to step 3 of Example 24. Green solid. MS (M+H) ⁺ = 562.4

Step 4. Synthesis of 3-((4-(((1-((1r,4r)-4-aminocyclohexyl)piperidin-4-yl)methyl)amino)phenyl)(methyl)amino)piperidine-2,6-dione (6)

The title compound (95 mg, crude, TFA) as a green oil was obtained by a similar method to step 4 of Example 24. MS (M+H) ⁺ = 428.4

Step 5. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((4-((2,6-dioxopiperidin-3-yl)(methyl)amino)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 27)

The title compound (8.1 mg, 9.77 μmol, 5.02% yield, 99% purity) was obtained as a white solid by a similar method to step 5 of Example 24. MS (M+H) ⁺ = 821.5

¹ H NMR (400 MHz, DMSO-d ₆ ) δ = 10.75 - 10.62 (m, 1H), 8.41 (d, J = 8.9 Hz, 1H), 8.07 - 7.97 (m, 1H), 7.90 (s, 1H), 7.62 (s, 1H), 7.50 - 7.44 (m, 2H), 6.71 - 6.64 (m, 2H), 6.51 - 6.44 (m, 2H), 4.99 - 4.91 (m, 1H), 4.58 - 4.50 (m, 1H), 4.47 - 4.39 (m, 1H), 4.36 - 4.27 (m, 1H), 3.94 (s, 3H), 3.77 - 3.67 (m, 1H), 3.24 (s, 3H), 2.85 - 2.75 (m, 4H), 2.63 (s, 3H), 2.57 - 2.53 (m, 1H), 2.46 - 2.40 (m, 1H), 2.28 - 2.07 (m, 4H), 2.04 - 1.97 (m, 1H), 1.92 - 1.70 (m, 12H), 1.66 - 1.59 (m, 2H), 1.46 - 1.28 (m, 5H), 1.24 - 1.20 (m, 3H), 1.18 - 1.09 (m, 2H)

Example 28. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)-[1,4'-bipiperidin]-1'-yl)-3-methoxybenzamide (Compound 28)

Step 1. Synthesis of tert-butyl 4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidine-1-carboxylate (3)

To a solution of 3-(4-aminophenyl)piperidine-2,6-dione (0.3 g, 1.47 mmol) and tert-butyl 4-formylpiperidine-1-carboxylate (360.00 mg, 1.69 mmol) in DCM (5 mL) and DMF (5 mL) were added AcOH (88.21 mg, 1.47 mmol) and NaBH(OAc) ₃ (622.67 mg, 2.94 mmol), and the resulting mixture was stirred at 20 °C for 14 h. The peak of the target mass (58%) was confirmed by LCMS. The mixture was diluted with water (20 mL) and extracted with DCM (20 mL x 3). The combined organic layer was washed with brine (50 mL), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (10 g SepaFlash® silica flash column, eluent of 0–50% EtOAc/Petroleum ether gradient @ 80 mL/min) to give the title compound (0.35 g, 871.74 μmol, 59.34% yield) as a yellow solid. MS(M+Na) ⁺ = 424.2

Step 2. Synthesis of 3-(4-((piperidin-4-ylmethyl)amino)phenyl)piperidine-2,6-dione (4)

A solution of tert-butyl 4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidine-1-carboxylate (200 mg, 498.13 μmol) in HCl/dioxane (2 M, 10.00 mL) was stirred at 20 °C for 1 h. The main peak of the desired mass was identified by LCMS. The mixture was concentrated under reduced pressure to obtain the title compound (180 mg, crude, HCl salt) as a brown solid. MS(M+H) ⁺ = 302.1

Step 3. Synthesis of 1,4-dioxa-8-azaspiro[4.5]decan-8-amine (6)

To a solution of tert-butyl (1,4-dioxa-8-azaspiro[4.5]decan-8-yl)carbamate (0.6 g, 2.32 mmol) in DCM (2 mL) was added TFA (3.07 g, 26.92 mmol, 2 mL), and the mixture was stirred at 20 °C for 2 h. TLC (Petroleum ether/EtOAc=2/1) confirmed the consumption of tert-butyl (1,4-dioxa-8-azaspiro[4.5]decan-8-yl)carbamate and the formation of a new spot. The mixture was concentrated under reduced pressure to obtain the title compound (650 mg, crude, TFA salt) as a yellow oil.

Step 4. Synthesis of (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxy-N-(1,4-dioxa-8-azaspiro[4.5]decan-8-yl)benzamide (8)

To a solution of (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoic acid (400 mg, 972.16 μmol) in DMF (5 mL) were added HATU (502.84 mg, 1.32 mmol) and DIPEA (427.29 mg, 3.31 mmol, 575.87 μL), and the resulting mixture was stirred at 20 °C for 1 h. Then, 1,4-dioxa-8-azaspiro[4.5]decan-8-amine (0.3 g, 1.10 mmol, TFA salt) was added, and the resulting mixture was stirred at 20 °C for 1 h. The peak of the target mass (41%) was confirmed by LCMS. The mixture was diluted with H ₂ O (50 mL) and extracted with EtOAc (30 mL x 3). The combined organic layer was washed with brine (100 mL), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (10 g SepaFlash® silica flash column, eluent of 0–100% EtOAc/Petroleum ether gradient @ 80 mL/min) to give the title compound (280 mg, 507.58 μmol, 46.06% yield) as a yellow solid. MS (M+H) ⁺ = 552.3

Step 5. Synthesis of (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxy-N-(4-oxopiperidin-1-yl)benzamide (9)

To a solution of (R)-4-(( ₈ -cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxy-N-(1,4-dioxa-8-azaspiro[4.5]decan-8-yl)benzamide (100 mg, 181.28 μmol) in H 2 O (0.5 mL) and dioxane (0.5 mL) was added HCOOH (8.71 mg, 181.28 μmol, 3 mL), and the mixture was stirred at 80 °C for 1 h. The major peak of the desired mass was identified by LCMS. The mixture was concentrated under reduced pressure, and the residue was diluted with H ₂ O (20 mL) and adjusted to pH=8~9 with NaHCO ₃ . The resulting suspension was extracted with EtOAc (10 mL x 3). The mixed organic layer was dried over Na ₂ SO ₄ and filtered. The filtrate was concentrated under reduced pressure to obtain the title compound (200 mg, crude) as a yellow solid. MS (M+H) ⁺ = 508.3

Step 6. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)-[1,4'-bipiperidin]-1'-yl)-3-methoxybenzamide (Compound 28)

To a solution of 3-(4-((piperidin-4-ylmethyl)amino)phenyl)piperidine-2,6-dione (66.56 mg, 197.01 μmol, HCl salt) and MgSO ₄ (118.57 mg, 985.06 μmol) in DMAC (2 mL) was added TEA (99.68 mg, 985.06 μmol, 137.11 μL), followed by (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxy-N-(4-oxopiperidin-1-yl)benzamide (100 mg, 197.01 μmol), and the mixture was stirred at 20 °C for 1 h. After that, NaBH ₃ CN (18.57 mg, 295.52 μmol) was added dropwise, and the suspension was stirred at 20°C for 49 h. The peak of the target mass was confirmed by LCMS. The mixture was diluted with H ₂ O (20 mL) and extracted with EtOAc (10 mL x 3). The combined organic layers were washed with brine (20 mL), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by prep-TLC (DCM/Methanol=10/1) and repurified by prep-HPLC (column: Phenomenex Luna C18 150*25 mm*10 um; mobile phase: [H ₂ O (0.1% TFA) - ACN]; gradient: 0% - 28% B over 15.0 min), and the eluate was lyophilized. The impurities were repurified by prep-HPLC (column: Waters xbridge 150*25 mm 10 μm; mobile phase: [H ₂ O (10 mM NH ₄ HCO ₃ ) - ACN]; gradient: 32% - 62% B over 9.0 min), and the eluate was lyophilized to obtain the title compound as a white solid (9.8 mg, 12.11 μmol, 6.15% yield, 98% purity). MS(M+H) ⁺ =793.6

^1H NMR (400 MHz, DMSO-d ₆ ) δ = 10.73 (s, 1H), 9.25 (s, 1H), 8.42 (d, J = 9.0 Hz, 1H), 7.90 (s, 1H), 7.63 (s, 1H), 7.47 - 7.37 (m, 2H), 6.89 (d, J = 8.4 Hz, 2H), 6.52 (d, J = 8.3 Hz, 2H), 5.58 (br t, J = 6.2 Hz, 1H), 4.49 - 4.38 (m, 1H), 4.36 - 4.29 (m, 1H), 3.94 (s, 3H), 3.63 (dd, J = 5.1, 10.5 Hz, 1H), 3.39 - 3.35 (m, 1H), 3.24 (s, 3H), 3.07 - 3.00 (m, 2H), 2.95 - 2.85 (m, 4H), 2.84 - 2.76 (m, 2H), 2.30 - 2.24 (m, 1H), 2.16 - 2.06 (m, 3H), 2.06 - 1.98 (m, 2H), 1.96 - 1.91 (m, 1H), 1.86 - 1.71 (m, 9H), 1.67 - 1.52 (m, 5H), 1.28 - 1.23 (m, 3H), 1.20 - 1.12 (m, 2H).

Example 29. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-(cyclopentyloxy)-N-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)-[1,4'-bipiperidin]-1'-yl)benzamide (Compound 29)

Step 1. Synthesis of (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-(cyclopentyloxy)-N-(4-oxopiperidin-1-yl)benzamide (2)

The title compound (34 mg, 44.2% yield) was obtained as a yellow solid by a similar method to step 5 of Example 28. MS[M+H] ⁺ = 562.30

Step 2. Synthesis of tert-butyl 4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidine-1-carboxylate (5)

3-(4-Aminophenyl)piperidine-2,6-dione (180 mg, 0.881 mmol, 1.0 eq) and tert-butyl 4-formylpiperidine-1-carboxylate (282 mg, 1.32 mmol, 1.5 eq) were dissolved in DCM (3.6 mL), acetic acid (0.151 mL, 2.64 mmol, 3.0 eq) was added, and the mixture was stirred at room temperature for 3 hours. NaBH(OAc) ₃ (560 mg, 2.64 mmol, 3.0 eq) was added, and the mixture was stirred at room temperature for 4 hours. The organic layer was extracted with saturated aqueous NaHCO ₃ solution (50 mL) and EtOAc (15 mL x 3), dried over MgSO ₄ , filtered, and concentrated under reduced pressure. The residue was purified by silica gel column chromatography (EtOAc/Hex, EtOAc 0 to 60% for 17 mins, 60 to 100% for 10 mins) to obtain the title compound (260 mg, 73.5% yield) as a yellow solid. MS[M+Na] ⁺ = 424.15

Step 3. Synthesis of 3-(4-((piperidin-4-ylmethyl)amino)phenyl)piperidine-2,6-dione (6)

tert-Butyl 4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidine-1-carboxylate (260 mg, 0.648 mmol, 1.0 eq) was dissolved in DCM (5.0 mL). After lowering the temperature to 0 ^o C, a 4 N HCl solution in dioxane (1.94 mL, 7.77 mmol, 12 eq) was added, and the temperature was raised to room temperature and stirred for 12 h. The solid was filtered with DCM to obtain a pale pink solid (230 mg, 94.9% yield). 100 mg of the solid fraction was purified by amine column chromatography (YAMAZEN Amino(NH2, 40~63㎛, 60Å), 7 g, DCM/MeOH, MeOH 0 to 10% for 15 mins) to obtain the title compound (44 mg). MS[M+H] ⁺ = 302.20

Step 4. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-(cyclopentyloxy)-N-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)-[1,4'-bipiperidin]-1'-yl)benzamide (Compound 29)

3-(4-((piperidin-4-ylmethyl)amino)phenyl)piperidine-2,6-dione (36.5 mg, 0.121 mmol, 2.0 eq), (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-(cyclopentyloxy)-N-(4-oxopiperidin-1-yl)benzamide (34 mg, 0.0605 mmol, 1.0 eq) were dissolved in N,N-dimethylacetamide (1.0 mL), AcOH (0.034 mL, 0.65 mmol, 10 eq) was added, and the mixture was stirred at room temperature for 1 hour. NaBH ₃ CN (19 mg, 0.303 mmol, 5 eq) was added and stirred for 36 h. The main peak of the desired mass was confirmed by LCMS. The mixture was purified using prep-HPLC (column: Agilent 10 Prep-C18 150*30 mm*10 μm; mobile phase: [H ₂ O (0.1% FA) - ACN (0.1% FA)]; gradient: 0% - 95% B over 42.0 min), and the residue was purified by amine column chromatography (YAMAZEN Amino(NH 2 , 40~63 μm, 60 Å), 7 g, DCM/MeOH, MeOH 0 to 10% for 12 mins) and lyophilized to obtain the title compound as a white solid (5 mg, 9.5% yield, 98.4% purity). MS[M+H] ⁺ = 847.40

^1H NMR (400 MHz, CDCl ₃ ) δ = 10.71 (s, 1H), 9.22 (s, 1H), 8.42 (d, J = 8.37 Hz, 1H), 7.88 (s, 1H), 7.54 (s, 1H), 7.40 (d, J = 9.75 Hz, 2H), 6.88 (d, J = 8.48 Hz, 2H), 6.51 (d, J = 8.36 Hz, 2H), 5.56 (s, 1H), 4.35 - 4.29 (m, 1H), 4.27 - 4.23 (m, 1H), 3.63 - 3.61 (m, 1H), 3.23 (s, 3H), 3.01 (s, 2H), 2.91 - 2.83 (m, 4H), 2.81 - 2.79 (m, 2H), 2.33(s, 1H), 2.27 - 2.18 (m, 2H), 2.13 - 2.07 (m, 2H)), 1.97 - 1.92 (m, 8H), 1.85 - 1.70 (m, 11H), 1.65 - 1.59 (m, 7H), 1.25 (d, J = 6.60 Hz, 3H), 1.17 - 1.14 (d, J = 10.16 Hz, 2H)

Example 30. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(((4-(2,6-dioxopiperidin-3-yl)-3-fluorophenyl)amino)methyl)-[1,4'-bipiperidin]-1'-yl)-3-methoxybenzamide (Compound 30)

Step 1. Synthesis of 4-(2,6-bis(benzyloxy)pyridin-3-yl)-3-fluoroaniline (3)

A mixture of 3-fluoro-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan- ₂ -yl)aniline (1 g, 4.22 mmol), 2,6-dibenzyloxy-3-bromo-pyridine (1.56 g, 4.22 mmol), Pd(dppf)Cl ₂ (308.63 mg, 421.80 μmol) and K ₂ CO ₃ (1.17 g, 8.44 mmol) in dioxane (16 mL) and H 2 O (4 mL) was degassed and purged three times with N ₂ , and the mixture was stirred at 90 °C under CN ₂ for 16 h. The peak of the target mass (62%) was identified by LCMS. The reaction mixture was diluted with water (15 mL) and extracted with EtOAc (20 mLХ3). The mixed organic layer was dried _{over Na2SO4 ,} filtered, and concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (12 g SepaFlash® silica flash column, eluent of 0–15% EtOAc/Petroleum ether gradient @ 80 mL/min) to give the title compound (1.63 g, 3.99 mmol, 94.57% yield, 98% purity) as a brown oil. MS (M+H) ⁺ = 401.2

^1H NMR (400 MHz, CDCl ₃ ) δ = 7.57 - 7.29 (m, 11H), 7.22 - 7.15 (m, 1H), 6.54 - 6.43 (m, 3H), 5.41 (s, 2H), 5.36 (s, 2H).

Step 2. Synthesis of 3-(4-amino-2-fluorophenyl)piperidine-2,6-dione (4)

Solution 1: 4-(2,6-Dibenzyloxy-3-pyridyl)-3-fluoro-aniline (1.6 g, 4.00 mmol) in THF (30 mL). The fixed bed (named FLR ₁ , volume 1 mL) was packed with a granular catalyst (Pd(OH) ₂ /Al ₂ O ₃ (1.12 g, 399.56 μmol, 5% purity)). The H ₂ pressure controller was adjusted to 1 MPa, and the H ₂ flow rate (H ₂ , 10 sccm) was set. Solution 1 was pumped by pump 1 (S ₁ , P1, 0.4 mL/min) and flowed into reactor 1 (FLR ₁ , SS, Fixed bed, 6.350 (1/4") mm, 1.0 mL, 50.0 °C). The reaction mixture was continuously collected from the reactor into a storage vessel. The peak of the desired mass was identified by LCMS. The reaction mixture was concentrated under reduced pressure. The residue was triturated with MTBE (10 mL) at 20 °C for 5 min to obtain the title compound (0.62 g, 2.43 mmol, 60.75% yield, 87% purity) as a pale pink solid. MS(M+H) ⁺ = 223.0

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.75 (s, 1H), 6.96 - 6.78 (m, 1H), 6.40 - 6.20 (m, 2H), 5.31 (s, 2H), 3.77 (dd, J = 5.0, 12.1 Hz, 1H), 2.76 - 2.63 (m, 1H), 2.46 (t, J = 3.7 Hz, 1H), 2.18 - 2.02(m, 1H), 1.98 - 1.79 (m, 1H)).

Step 3. Synthesis of tert-butyl 4-(((4-(2,6-dioxopiperidin-3-yl)-3-fluorophenyl)amino)methyl)piperidine-1-carboxylate (6)

The title compound (120 mg, 286.06 μmol, 31.78% yield) was obtained as a white solid by a similar method to step 2 of Example 29. MS(M-Boc+H) ⁺ = 320.2

Step 4. Synthesis of 3-(2-fluoro-4-((piperidin-4-ylmethyl)amino)phenyl)piperidine-2,6-dione (7)

A mixture of tert-butyl 4-(((4-(2,6-dioxopiperidin-3-yl)-3-fluorophenyl)amino)methyl)piperidine-1-carboxylate (120 mg, 286.06 μmol) in HCl/dioxane (2 M, 5 mL) was stirred at 20 °C for 14 h. The peak of the target mass (85%) was identified by LCMS, and the mixture was concentrated under reduced pressure to obtain the title compound (100 mg, 281.03 μmol, 98.24% yield, HCl) as a white solid. MS(M+H) ⁺ = 320.1

Step 5. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(((4-(2,6-dioxopiperidin-3-yl)-3-fluorophenyl)amino)methyl)-[1,4'-bipiperidin]-1'-yl)-3-methoxybenzamide (Compound 30)

To a solution of 3-(2-fluoro-4-((piperidin-4-ylmethyl)amino)phenyl)piperidine-2,6-dione (100.00 mg, 281.03 μmol, HCl) and (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxy-N-(4-oxopiperidin-1-yl)benzamide (120 mg, 236.41 μmol) in DMAC (5 mL) were added TEA (119.61 mg, 1.18 mmol, 164.53 μL) and MgSO ₄ (142.28 mg, 1.18 mmol), and the mixture was stirred at 20 °C for 1 h. NaBH ₃ CN (22.29 mg, 354.62 μmol) was added, and the mixture was stirred at 20 °C for 16 h. The main peak of the target mass was identified by LCMS. The mixture was diluted with H ₂ O (20 mL), extracted with EtOAc (10 mL x 3), and the combined organic layers were washed with brine (20 mL), dried over Na ₂ SO ₄ , filtered, and the filtrate was concentrated under reduced pressure. The residue was purified by prep-HPLC (column: Phenomenex Luna C18 150*25 mm*10 um; mobile phase: [H ₂ O (0.1% TFA) -ACN]; gradient: 0%-30% B over 15.0 min), and the eluate was lyophilized. The product was dissolved in H ₂ O (20 mL) and adjusted to pH=8~9 with NaHCO ₃ . The resulting suspension was extracted with EtOAc (10 mL x 3), and the mixed organic layer was dried over Na ₂ SO ₄ and filtered. The filtrate was concentrated under reduced pressure, and the residue was lyophilized to obtain the title compound (10.8 mg, 12.52 μmol, 5.30% yield, 94% purity) as a white solid. MS(M+H) ⁺ = 811.6

^1H NMR (400 MHz, DMSO _- d6 ) δ = 10.76 (s, 1H), 9.25 (s, 1H), 8.42 (d, J = 8.9 Hz, 1H), 7.90 (s, 1H), 7.63 (s, 1H), 7.45 - 7.36 (m, 2H), 6.91 (t, J = 8.6 Hz, 1H), 6.41 - 6.27 (m, 2H), 5.94 (t, J = 5.3 Hz, 1H), 4.48 - 4.38 (m, 1H), 4.36 - 4.29 (m, 1H), 3.93 (s, 3H), 3.79 (dd, J = 5.0, 12.1 Hz, 1H), 3.24 (s, 3H), 3.08 - 2.99 (m, 2H), 2.95 - 2.83 (m, 4H), 2.83 - 2.73 (m, 2H), 2.72 - 2.63 (m, 1H), 2.49 - 2.46 (m, 1H), 2.32 - 2.21 (m, 1H), 2.18 - 2.05 (m, 3H), 2.04 - 1.98 (m, 1H), 1.98 - 1.90 (m, 2H), 1.84 - 1.70 (m, 8H), 1.66 - 1.47 (m, 5H), 1.23 (d, J = 6.8 Hz, 3H), 1.21 - 1.09 (m, 2H).

Example 31. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(((4-(2,6-dioxopiperidin-3-yl)-3-methylphenyl)amino)methyl)-[1,4'-bipiperidin]-1'-yl)-3-methoxybenzamide (Compound 31)

Step 1. Synthesis of 4-(2,6-bis(benzyloxy)pyridin-3-yl)-3-methylaniline (3)

A mixture of 3-methyl-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan- ₂ -yl)aniline (1 g, 4.29 mmol), 2,6-dibenzyloxy-3-bromo-pyridine (1.59 g, 4.29 mmol), Pd(dppf)Cl ₂ (313.88 mg, 428.98 μmol) and K ₂ CO ₃ (1.19 g, 8.58 mmol) in dioxane (16 mL) and H 2 O (4 mL) was degassed and purged three times with N ₂ , and the mixture was stirred at 100 °C under N ₂ for 16 h. The peak of the target mass (70%) was identified by LCMS. The reaction mixture was diluted with water (15 mL) and extracted with EtOAc (20 mLХ3). The mixed organic layer was dried _{over Na2SO4 ,} filtered, and concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (12 g SepaFlash® silica flash column, eluent of 0–15% EtOAc/Petroleum ether gradient @ 80 mL/min) to give the title compound (1.6 g, 3.83 mmol, 89.37% yield, 95% purity) as a brown oil. MS(M+H) ⁺ = 397.1

^1H NMR (400 MHz, CDCl ₃ ) δ = 7.51 - 7.29 (m, 10H), 7.27 - 7.23 (m, 1H), 6.97 (d, J = 7.9 Hz, 1H), 6.64 - 6.53 (m, 2H), 6.43 (d, J = 7.8 Hz, 1H), 5.39 (s, 2H), 5.35 (s, 2H), 2.08 (s, 3H).

Step 2. Synthesis of 3-(4-amino-2-methylphenyl)piperidine-2,6-dione (4)

Solution 1: 4-(2,6-bis(benzyloxy)pyridin-3-yl)-3-methylaniline (1.6 g, 4.04 mmol) in THF (30 mL). The fixed bed (named FLR ₁ , volume 1 mL) was packed with a granular catalyst (Pd(OH) ₂ /Al ₂ O ₃ (1.13 g, 403.55 μmol, 5% purity)). The H ₂ pressure regulator was adjusted to 1 MPa, and the H ₂ flow rate (H 2 , 10 sccm) was adjusted. Solution 1 was pumped by pump 1 (S ₁ , P1, 0.4 mL/min) and flowed into reactor 1 (FLR ₁ , SS, Fixed bed, 6.350 (1/4") mm, 1.0 mL, 50.0 °C). The reaction mixture was continuously collected from the reactor into a storage vessel. The peak of the desired mass was identified by LCMS. The reaction mixture was concentrated under reduced pressure. The residue was triturated with MTBE (10 mL) at 20 °C for 5 min to obtain the title compound (0.42 g, 1.69 mmol, 41.96% yield, 88% purity) as a green solid. MS (M+H) ⁺ = 219.0

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.72 (s, 1H), 6.71 (d, J = 8.1 Hz, 1H), 6.47 - 6.25 (m, 2H), 4.88 (s, 2H), 3.81 (dd, J = 5.0, 11.1 Hz, 1H), 2.76 - 2.58 (m, 1H), 2.49 - 2.42 (m, 1H), 2.11 (s, 3H), 2.08 - 2.00 (m, 1H), 1.97 - 1.87 (m, 1H).

Step 3. Synthesis of tert-butyl 4-(((4-(2,6-dioxopiperidin-3-yl)-3-methylphenyl)amino)methyl)piperidine-1-carboxylate (6)

The title compound (120 mg, 288.79 μmol, 31.51% yield) was obtained as a white solid by a similar method to step 2 of Example 29. MS(M-Boc+H) ⁺ = 316.3

Step 4. Synthesis of 3-(2-methyl-4-((piperidin-4-ylmethyl)amino)phenyl)piperidine-2,6-dione (7)

A mixture of tert-butyl 4-(((4-(2,6-dioxopiperidin-3-yl)-3-methylphenyl)amino)methyl)piperidine-1-carboxylate (120 mg, 288.79 μmol) in HCl/dioxane (2 M, 5 mL) was stirred at 20 °C for 14 h. The peak of the target mass (83%) was identified by LCMS, and the mixture was concentrated under reduced pressure to obtain the title compound (100 mg, 284.20 μmol, 98.41% yield, HCl) as a white solid. MS(M+H) ⁺ = 316.1

Step 5. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(((4-(2,6-dioxopiperidin-3-yl)-3-methylphenyl)amino)methyl)-[1,4'-bipiperidin]-1'-yl)-3-methoxybenzamide (Compound 31)

The title compound (10.5 mg, 12.62 μmol, 5.34% yield, 97% purity) was obtained as a white solid by a similar method to step 3 of Example 50. MS(M+H) ⁺ = 807.6

^1H NMR (400 MHz, DMSO _- d6 ) δ = 10.73 (s, 1H), 9.25 (s, 1H), 8.42 (d, J = 8.8 Hz, 1H), 7.90 (s, 1H), 7.63 (s, 1H), 7.47 - 7.35 (m, 2H), 6.76 (d, J = 8.3 Hz, 1H), 6.40 - 6.30 (m, 2H), 5.47 (t, J = 5.7 Hz, 1H), 4.48 - 4.38 (m, 1H), 4.37 - 4.28 (m, 1H), 3.93 (s, 3H), 3.81 (dd, J = 5.1, 11.2 Hz, 1H), 3.24 (s, 3H), 3.03 (d, J = 9.8 Hz, 2H), 2.93 - 2.83 (m, 4H), 2.83 - 2.78 (m, 2H), 2.72 - 2.64 (m, 1H), 2.29 - 2.22 (m, 1H), 2.14 (s, 3H), 2.12 - 1.97 (m, 4H), 1.96 - 1.90 (m, 2H), 1.87 - 1.68 (m, 9H), 1.64 - 1.47 (m, 5H), 1.23 (d, J = 6.8 Hz, 3H), 1.21 - 1.10 (m, 2H).

Example 32. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(((6-(2,6-dioxopiperidin-3-yl)pyridin-3-yl)amino)methyl)-[1,4'-bipiperidin]-1'-yl)-3-methoxybenzamide (Compound 32)

Step 1. Synthesis of tert-butyl 4-(((6-(2,6-dioxopiperidin-3-yl)pyridin-3-yl)amino)methyl)piperidine-1-carboxylate (3)

The title compound (600 mg, 1.48 mmol, 70.43% yield, 99% purity) was obtained as a green solid by a similar method to step 2 of Example 29. MS(M+H) ⁺ = 403.3

Step 2. Synthesis of 3-(5-((piperidin-4-ylmethyl)amino)pyridin-2-yl)piperidine-2,6-dione (4)

To a solution of tert-butyl 4-(((6-(2,6-dioxopiperidin-3-yl)pyridin-3-yl)amino)methyl)piperidine-1-carboxylate (400 mg, 993.82 μmol) in DCM (10 mL) was added TFA (3.84 g, 33.66 mmol, 2.5 mL). The mixture was stirred at 25 °C for 1 h. LCMS confirmed complete consumption of the starting material and the peak of the desired mass. The mixture was concentrated under reduced pressure to give the title compound (413.82 mg, 993.82 μmol, 100.00% yield, TFA salt) as a brown oil.

Step 3. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(((6-(2,6-dioxopiperidin-3-yl)pyridin-3-yl)amino)methyl)-[1,4'-bipiperidin]-1'-yl)-3-methoxybenzamide (Compound 32)

To a solution of 3-(5-((piperidin-4-ylmethyl)amino)pyridin-2-yl)piperidine-2,6-dione (413.82 mg, 993.82 μmol, TFA salt) in DCM (20 mL) was added TEA (502.82 mg, 4.97 mmol, 691.63 μL) and MgSO ₄ (598.12 mg, 4.97 mmol) at 0 °C, followed by (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxy-N-(4-oxopiperidin-1-yl)benzamide (496.33 mg, 894.44 μmol). The mixture was stirred at 25 °C for 30 min. Then, NaBH(OAc) ₃ (631.89 mg, 2.98 mmol) was added, and the mixture was stirred at 40 °C for 16 h. The peak of the desired mass (63%) was confirmed by LCMS. The reaction mixture was diluted with NaHCO ₃ (30 mL) and extracted with DCM (50 mL x 3). The combined organic layer was washed with brine (20 mL x 2), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (20 g SepaFlash® silica flash column, eluent of 0–10% MeOH/DCM @ 40 mL/min) to give the title compound (248.7 mg, 284.41 μmol, 28.62% yield, 92.4% purity) as an off-white solid. MS(M+H) ⁺ =808.5.

^1H NMR (400 MHz, DMSO _- d6 ) δ = 10.73 (s, 1H), 9.24 (s, 1H), 8.41 (d, J = 8.8 Hz, 1H), 7.86 (d, J = 2.6 Hz, 1H), 7.84 (s, 1H), 7.59 (s, 1H), 7.44 - 7.37 (m, 2H), 7.01 (d, J = 8.4 Hz, 1H), 6.88 (dd, J = 2.8, 8.4 Hz, 1H), 5.86 (br t, J = 5.4 Hz, 1H), 4.35 (quin, J = 7.9 Hz, 1H), 4.23 (dd, J = 3.5, 7.6 Hz, 1H), 3.93 (s, 3H), 3.78 (dd, J = 5.4, 8.3 Hz, 1H), 3.24 (s, 3H), 3.07 - 2.99 (m, 2H), 2.93 - 2.85 (m, 4H), 2.78 (br t, J = 10.3 Hz, 2H), 2.54 - 2.52 (m, 1H), 2.28 - 2.21 (m, 1H), 2.16 - 2.05 (m, 4H), 2.03 - 1.96 (m, 1H), 1.93 - 1.88 (m, 1H), 1.87 - 1.83 (m, 1H), 1.80 - 1.70 (m, 8H), 1.68 - 1.44 (m, 7H), 1.24 - 1.11 (m, 2H), 0.76 (t, J = 7.4 Hz, 3H)

Example 33. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(((3-(2,6-dioxopiperidin-3-yl)-1-methyl-1H-indazol-6-yl)amino)methyl)-[1,4'-bipiperidin]-1'-yl)-3-methoxybenzamide (Compound 33)

Step 1. Synthesis of tert-butyl(3-(2,6-bis(benzyloxy)pyridin-3-yl)-1-methyl-1H-indazol-6-yl)carbamate (3)

A mixture of 3-(2,6-bis(benzyloxy)pyridin-3-yl)-6-bromo-1-methyl-1H-indazole (500 mg, 999.23 μmol), tert-butyl carbamate (233.33 mg, 1.99 mmol), XPhos Pd G3 (90.00 mg, 106.33 μmol), and K ₂ CO ₃ (414.30 mg, 3.00 mmol) in dioxane (15 mL) was degassed, purged three times with N ₂ , and stirred at 110 °C under CN ₂ for 16 h. The major peak of the desired mass was identified by LCMS. The reaction mixture was filtered. The filtered solid was washed with EtOAc (60 mL), and the filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (Biotage; 12 g SepaFlash® silica flash column, 15–30% EtOAc:Petroleum ether gradient, 120 mL/min) to give the title compound (500 mg, 931.76 μmol, yield 93.25%) as a pale yellow solid. MS [M+ H] ⁺ = 537.3

Step 2. tert-Butyl(3-(2,6-dioxopiperidin-3-yl)-1-methyl-1H-indazol-6-yl)carbamate

(4) Synthesis of

To a solution of Pd/C (600 mg, purity 10%) in THF (30 mL) was slowly added tert-butyl (3-(2,6-bis(benzyloxy)pyridin-3-yl)-1-methyl-1H-indazol-6-yl)carbamate (600 mg, 1.12 mmol) under N ₂ , and the mixture was stirred at 50°C under CH ₂ (45 Psi) for 16 h. The major peak of the desired mass was identified by LCMS. The mixture was filtered, and the filter cake was washed with THF (200 mL). The filtrate was concentrated under reduced pressure to give the title compound (420 mg, crude) as a white solid. MS [M+H] ⁺ = 359.2.

Step 3. Synthesis of 3-(6-amino-1-methyl-1H-indazol-3-yl)piperidine-2,6-dione (5)

Formic acid (6.32 mL, 167 mmol) was added to tert-butyl(3-(2,6-dioxopiperidin-3-yl)-1-methyl-1H-indazol-6-yl)carbamate (200 mg, 0.558 mmol) and stirred for 14 hours. The mixture was concentrated under reduced pressure, dissolved in THF (3 mL) and water (1.5 mL), 12 M HCl(aq) (1.5 mL) was added, and stirred for 1 hour. The mixture was adjusted to pH = 7 with saturated aqueous NaHCO ₃ solution (100 mL), and extracted twice with EtOAc (20 mL). The extracted organic layer was dried over MgSO ₄ , filtered, and concentrated under reduced pressure to obtain the title compound (153 mg, crude) as a light brown solid.

MS [M+H] ⁺ =259.1.

Step 4. Synthesis of tert-butyl 4-(((3-(2,6-dioxopiperidin-3-yl)-1-methyl-1H-indazol-6-yl)amino)methyl)piperidine-1-carboxylate (7)

A mixture of 3-(6-amino-1-methyl-1H-indazol-3-yl)piperidine-2,6-dione (153 mg, 0.593 mmol), tert-butyl 4-formylpiperidine-1-carboxylate (190 mg, 0.890 mmol), and acetic acid (33.9 uL, 0.593 mmol) in DCM (9.19 mL) was stirred at room temperature for 30 min. NaBH(OAc) ₃ (377 mg, 1.78 mmol) was added, and the mixture was stirred at room temperature for 13 h. TLC (EtOAc=100%) confirmed that the starting material was consumed. DCM (10 mL) was added to dilute, filtered through Celite, and washed with DCM (10 mL). The filtrate was dried under reduced pressure and purified by amine column chromatography (EtOAc = 0 to 100%, for 25 mins) to obtain the title compound (161 mg, 59.5% yield) as a white solid. MS [M+H] ⁺ = 456.2.

Step 5. Synthesis of 3-(1-methyl-6-((piperidin-4-ylmethyl)amino)-1H-indazol-3-yl)piperidine-2,6-dione (8)

To a solution of tert-butyl 4-(((3-(2,6-dioxopiperidin-3-yl)-1-methyl-1H-indazol-6-yl)amino)methyl)piperidine-1-carboxylate (161 mg, 0.353 mmol) in DCM (3.5 mL) was added a 4 M HCl solution in dioxane (1.06 mL, 4.24 mmol), and the mixture was stirred at room temperature for 3 h. The mixture was concentrated under reduced pressure to leave about 2 mL of the solvent, and diethyl ether (10 mL) was added. The resulting solid was filtered and dried to give the title compound (138 mg, 73.2%, HCl salt) as a beige solid. MS [M+H] ⁺ = 356.2.

Step 6. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(((3-(2,6-dioxopiperidin-3-yl)-1-methyl-1H-indazol-6-yl)amino)methyl)-[1,4'-bipiperidin]-1'-yl)-3-methoxybenzamide (Compound 33)

To a solution of 3-(1-methyl-6-((piperidin-4-ylmethyl)amino)-1H-indazol-3-yl)piperidine-2,6-dione (38.2 mg, 0.0975 mmol, HCl salt) in DMAC (1.3 mL) was added TEA (45.3 uL, 0.325 mmol) and stirred at room temperature for 15 minutes. (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxy-N-(4-oxopiperidin-1-yl)benzamide (33 mg, 0.0650 mmol), acetic acid (37.2 uL, 0.650 mmol), and MgSO ₄ (54.8 mg, 0.455 mmol) were added to the reaction mixture, and the mixture was stirred at room temperature for 7 hours. NaBH ₃ CN (10.2 mg, 0.163 mmol) was added to the reaction mixture, and the mixture was stirred at room temperature for 48 hours. LCMS confirmed that all starting materials were consumed, and the main peak of the desired mass was confirmed. The mixture was filtered through Celite, purified using prep-HPLC (Column: Agilent 10 Prep-C18 150*30 mm*10um; Mobile phase: [H ₂ O (0.1% FA) - ACN (0.1% FA)]; Gradient: 0% - 95% B over 42.0 min), and the solvent was concentrated to obtain a residue. The residue was purified by amine column chromatography (MeOH:MC=1:50 to 1:20, for 20 mins) and lyophilized to obtain the title compound (16.1 mg, 29.2% yield, 97.7% purity) as a white solid. MS[M+H] ⁺ = 847.4.

¹ H NMR (400 MHz, , DMSO- d ₆ ) δ = 10.81 (s, 1H), 9.24 (s, 1H) 8.41 (d, J = 8.7 Hz, 1H), 7.89 (s, 1H), 7.62 (s, 1H), 7.42 - 7.40 (m, 2H), 7.31 (d, J = 8.7 Hz, 1H), 6.56 (d, J = 8.8 Hz, 1H), 6.31 (s, 1H), 5.93 -5.91 (m, 1H), 4.44 - 4.40 (m, 1H), 4.32 (q, J =6.8 Hz, 1H), 4.19 - 4.16 (m, 1H), 3.93 (s, 3H), 3.81 (s, 3H), 3.23 (s, 3H), 3.05 - 3.02 (m, 2H), 2.96 - 2.95 (m, 2H), 2.92 - 2.89 (m, 2H), 2.81 - 2.76 (m, 2H), 2.62 - 2.60 (m, 2H), 2.26 - 2.23 (m, 2H), 2.17 - 2.12 (m, 2H), 2.01 - 1.99 (m, 1H), 1.94 - 1.92 (m, 1H), 1.78 - 1.74 (m, 9H), 1.60 - 1.58 (m, 5H), 1.23 (d, J = 6.7 Hz, 3H), 1.19 - 1.18 (m, 2H)

Example 34. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(3-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)azetidin-1-yl)piperidin-1-yl)-3-methoxybenzamide (Compound 34)

Step 1. Synthesis of tert-butyl 3-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)azetidine-1-carboxylate (3)

To a solution of 3-(4-aminophenyl)piperidine-2,6-dione (0.3 g, 1.47 mmol) and tert-butyl 3-formylazetidine-1-carboxylate (299.29 mg, 1.62 mmol) in DCM (10 mL) and DMF (2 mL) was added AcOH (104.90 mg, 1.75 mmol, 100.00 μL) at 20 °C. After stirring for 1 h, NaBH(OAc) ₃ (934.00 mg, 4.41 mmol) was added at 20 °C, and the resulting mixture was stirred at 20 °C for 12 h. LCMS confirmed the remaining starting material and the peak of the target mass. The reaction mixture was diluted with H ₂ O (20 mL) and extracted with DCM (20 mL x 3). The organic layer was washed with saturated NaHCO ₃ (20 mL x 3), dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (10 g SepaFlash® silica flash column, eluent of 33–100% EtOAc/Petroleum ether gradient @ 200 mL/min) and repurified by prep-HPLC (column: Phenomenex Luna C18 150*25 mm*10 um; mobile phase: [H ₂ O (0.1% TFA) - ACN]; gradient: 5% - 35% B over 15.0 min). The eluate was lyophilized to obtain the title compound (110 mg, 294.55 μmol, 20.05% yield) as a white solid. MS (M-100+H) ⁺ = 274.1

Step 2. Synthesis of 3-(4-((azetidin-3-ylmethyl)amino)phenyl)piperidine-2,6-dione (4)

To a solution of tert-butyl 3-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)azetidine-1-carboxylate (110 mg, 294.55 μmol) in DCM (3 mL) was added TFA (1 mL) at 20 °C, and the resulting mixture was stirred at 20 °C for 2 h. LCMS confirmed complete consumption of the starting material and the peak of the target mass (97%). The reaction mixture was concentrated under reduced pressure to obtain the title compound (115 mg, crude, TFA salt) as a yellow oil. MS(M+H) ⁺ = 274.1

Step 3. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(3-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)azetidin-1-yl)piperidin-1-yl)-3-methoxybenzamide (Compound 34)

To a solution of 3-(4-((azetidin-3-ylmethyl)amino)phenyl)piperidine-2,6-dione (91.58 mg, 236.41 μmol, TFA salt) and (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxy-N-(4-oxopiperidin-1-yl)benzamide (60 mg, 118.21 μmol) in DMAC (4 mL) was added TEA (71.77 mg, 709.24 μmol, 98.72 μL) at 20 °C. After stirring for 0.5 h, NaBH ₃ CN (22.29 mg, 354.62 μmol) was added at 20 °C for 12 h. LCMS confirmed that the starting material was completely consumed and the peak of the target mass (81%) was observed. The reaction mixture was diluted with H ₂ O (20 mL) and extracted with EtOAc (20 mL x 3). The organic layer was washed with brine (20 mL x 3), dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure. The residue was purified by prep-HPLC (column: Phenomenex Luna C18 150*25 mm*10 um; mobile phase: [H ₂ O (0.1% TFA) - ACN]; gradient: 0% - 28% B over 15.0 min). The eluate was adjusted to pH = ~8 with saturated NaHCO ₃ , and extracted with DCM (20 mL x 2). The organic layer was dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure. The product was dissolved in a mixed solution (20 mL, ACN:H ₂ O=1:1) and lyophilized to obtain the title compound as a white solid (10.5 mg, 12.22 μmol, 10.34% yield, 89% purity). MS(M+H) ⁺ =765.4

¹ H NMR (400 MHz, DMSO- d ₆ ) δ = 10.72 (br s, 1H), 9.26 (s, 1H), 8.44 - 8.38 (m, 1H), 7.89 (s, 1H), 7.63 - 7.58 (m, 1H), 7.46 - 7.36 (m, 2H), 6.90 (d, J = 8.6 Hz, 2H), 6.51 (d, J = 8.4 Hz, 2H), 5.58 (t, J = 5.5 Hz, 1H), 4.47 - 4.37 (m, 1H), 4.32 (q, J = 6.4 Hz, 1H), 3.93 (s, 3H), 3.63 (dd, J = 4.9, 10.6 Hz, 1H), 3.27 - 3.22 (m, 5H), 3.15 (br t, J = 6.0 Hz, 2H), 3.02 - 2.93 (m, 2H), 2.84 (br t, J = 6.5 Hz, 2H), 2.79 - 2.71 (m, 2H), 2.65 - 2.53 (m, 2H), 2.46 - 2.42 (m, 1H), 2.10 - 1.97 (m, 4H), 1.95 - 1.89 (m, 1H), 1.84 - 1.77 (m, 3H), 1.65 - 1.60 (m, 2H), 1.32 - 1.26 (m, 2H), 1.23 (d, J = 6.6 Hz, 3H), 1.17 - 1.13 (m, 1H), 0.88 - 0.82 (m, 1H), 0.80 - 0.71 (m, 1H)

Example 35. Synthesis of 1'-(4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzamido)-N-(4-(2,6-dioxopiperidin-3-yl)phenyl)-[1,4'-bipiperidine]-4-carboxamide (Compound 35)

Step 1. Synthesis of 1-benzyl 4-methyl piperidine-1,4-dicarboxylate (2)

To a mixture of methyl piperidine-4-carboxylate (1.0 g, 6.98 mmol, 1.0 eq) and benzyl carbonochloridate (1.3 mL, 9.08 mmol, 1.3 eq) in DCM (20 mL) was added TEA (1.46 mL, 10.5 mmol, 1.5 eq) at 0 ^o C, the mixture was warmed to room temperature, and stirred for 23 h. The organic layer was extracted with saturated aqueous NaCl solution (50 mL) and EtOAc (30 mL x 3), dried over MgSO ₄ , filtered, and concentrated under reduced pressure to obtain a residue. The residue was purified by silica column chromatography (Hex/EA, EA 0 to 30% for 12 mins) to obtain the title compound (1.36 g, 70.2% yield) as a yellow solid. MS[M+H] ⁺ = 278.10

Step 2. Synthesis of 1-((benzyloxy)carbonyl)piperidine-4-carboxylic acid (3)

A mixture of 1-benzyl 4-methyl piperidine-1,4-dicarboxylate (1.32 g, 4.76 mmol, 1.0 eq) and LiOH·H ₂ O (0.599 g, 14.3 mmol, 3.0 eq) in MeOH (10 mL) and THF (3 mL) was stirred at 40 ^o C for 3 h. The organic layer was extracted with 1 N aqueous HCl solution and EtOAc, dried over MgSO ₄ , filtered, and concentrated under reduced pressure to obtain the title compound (1.36 g, crude) as a yellow solid. MS [M + H] ⁺ = 264.10

Step 3. Synthesis of benzyl 4-((4-(2,6-dioxopiperidin-3-yl)phenyl)carbamoyl)piperidine-1-carboxylate (5)

To a solution of 1-((benzyloxy)carbonyl)piperidine-4-carboxylic acid (200 mg, 0.760 mmol, 1.0 eq), 3-(4-aminophenyl)piperidine-2,6-dione (186 mg, 0.912 mmol, 1.2 eq), and HATU (0.433 mg, 1.14 mmol, 1.5 eq) in DMF (2 mL) was added DIPEA (0.407 mL, 2.28 mmol, 3.0 eq) at 0 ^o C, warmed to room temperature, and stirred for 15 h. Extract the organic layer using saturated aqueous NaHCO ₃ solution (50 mL) and EtOAc (30 mL x 3), dried over MgSO ₄ , filtered, and concentrated under reduced pressure. The title compound (280 mg, 82.0% yield) was obtained as a yellow solid by purification using silica column chromatography (DCM/MeOH, MeOH 0 to 10% for 25 mins). MS[M+H] ⁺ = 450.20

Step 4. Synthesis of N-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidine-4-carboxamide (6)

A mixture of benzyl 4-((4-(2,6-dioxopiperidin-3-yl)phenyl)carbamoyl)piperidine-1-carboxylate (280 mg, 0.623 mmol, 1.0 eq) in TFA (9.25 mL, 125 mmol, 200 eq) was stirred at 40 ^o C for 4 h, then concentrated under reduced pressure to remove TFA. The residue was purified by amine column chromatography (YAMAZEN Amino(NH ₂ , 40~63 μm, 60 Å), 7 g, DCM/MeOH, MeoH 0 to 20% for 15 mins) to obtain the title compound (80 mg, 0.254 mmol, 40.7% yield) as a yellow solid. MS[M+H] ⁺ = 316.10

Step 5. Synthesis of 1'-(4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzamido)-N-(4-(2,6-dioxopiperidin-3-yl)phenyl)-[1,4'-bipiperidine]-4-carboxamide (Compound 35)

The title compound (3.3 mg, 4.89% yield, 94.1% purity) was obtained as a white solid by a similar method to step 4 of Example 29. MS[M+H] ⁺ = 807.35

^1H NMR (400 MHz, CDCl ₃ ) δ = 10.79 (s, 1H), 9.81 (s, 1H), 9.25 (s, 1H), 8.42 (d, J = 8.72 Hz, 1H), 7.90 (s, 1H), 7.62 (s, 1H), 7.55 (d, J = 8.56 Hz, 2H), 7.42 - 7.41 (m, 2H), 7.13 (d, J = 8.60 Hz, 2H), 4.42 (t, J = 8.15 Hz, 1H), 4.32 (q, J = 6.68 Hz 1H), 3.94 (s, 3H), 3.79 (dd, J = 11.1 Hz, J = 4.38 Hz, 2H), 3.22 (s, 3H), 3.06 - 3.03 (m, 2H), 2.97 - 2.94 (d, J = 11.1 Hz, 2H), 2.83 - 2.78 (m, 2H), 2.68 - 2.67 (m, 1H), 2.33 (s,1H), 2.30 - 2.29 (m, 2H), 2.18 - 2.13 (m, 2H), 2.04 - 1.99 (m, 2H), 1.94 - 1.92 (m, 1H), 1.82 - 1.73 (m, 8H), 1.68 - 1.56 (m, 6H), 1.23 (d, J = 6.64 Hz, 3H)

Example 36. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)-[1,4'-bipiperidin]-1'-yl)-3-methoxybenzamide (Compound 36)

Step 1. Synthesis of tert-butyl 4-((4-(2,6-bis(benzyloxy)pyridin-3-yl)phenyl)amino)piperidine-1-carboxylate (2)

To a solution of 2,6-bis(benzyloxy)-3-(4-bromophenyl)pyridine (200 mg, 0.448 mmol, 1 eq) in 1,4-dioxane (2.2 mL) were added tert-Butyl 4-aminopiperidine-1-carboxylate (108 mg, 0.538 mmol, 1.2 eq), tBuXPhos Pd G3 (17.8 mg, 0.0224 mmol, 0.05 eq), and tBuOK (151 mg, 1.34 mmol, 3 eq). The reaction solution was stirred at 80°C for 1 h. The main peak of the desired mass was confirmed by LCMS. After adding EtOAc and brine, the mixture was extracted with EtOAc, and the organic layer was dried over MgSO ₄ , filtered, and concentrated under reduced pressure. The residue was purified by silica gel column chromatography (EtOAc:Hexane=1:9 to 1:4) to obtain the title compound (172.2 mg, 68.0% yield) as a yellow solid. MS[M+H] ⁺ = 566.2

Step 2. Synthesis of tert-butyl 4-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)piperidine-1-carboxylate (3)

To a solution of tert-butyl 4-((4-(2,6-bis(benzyloxy)pyridin-3-yl)phenyl)amino)piperidine-1-carboxylate (172 mg, 0.304 mmol, 1 eq) in MeOH (1.5 mL) was added Pd/C (172 mg, 0.162 mmol, 0.532 eq) and stirred under H ₂ for 2 h. The main peak of the desired mass was confirmed by LCMS. The residue was filtered through Celite and concentrated under reduced pressure to give the title compound (96.9 mg, 82.3% yield) as a yellow solid. MS[M+H] ⁺ = 388.2

Step 3. Synthesis of 3-(4-(piperidin-4-ylamino)phenyl)piperidine-2,6-dione (4)

The title compound (75.3 mg, 55.6% yield) was obtained as a pink solid by a similar method to step 3 of Example 29. MS[M+H] ⁺ = 288.15

Step 4. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)-[1,4'-bipiperidin]-1'-yl)-3-methoxybenzamide (Compound 36)

A mixture of (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxy-N-(4-oxopiperidin-1-yl)benzamide (20.0 mg, 0.0284 mmol, 1.0 eq), 3-(4-(piperidin-4-ylamino)phenyl)piperidine-2,6-dione (22.6 mg, 0.079 mmol, 2.0 eq), and AcOH (0.023 mL, 0.394 mmol, 10 eq) in N,N-dimethylacetamide (0.4 mL) was stirred at room temperature for 1 h. NaBH(OAc) ₃ (7.43 mg, 0.118 mmol, 3 eq) was added and stirred for 15 h. The main peak of the desired mass was confirmed by LCMS. Saturated NaHCO ₃ aqueous solution (5 mL) was added to the mixture, extracted twice with EtOAc (5 mL x 2), dried over MgSO ₄ , filtered, and concentrated under reduced pressure to obtain the residue. The residue was purified by amine column chromatography (MeOH:MC = 1:20 to 1:10) to obtain the residue. After purification using prep-HPLC (column: Agilent 10 Prep-C18 150*30 mm*10 um; mobile phase: [H ₂ O (0.1% FA) - ACN (0.1% FA)]; gradient: 0% - 95% B over 42.0 min), the residue was lyophilized to obtain the title compound as a white solid (2.20 mg, 6.86% yield, 95.7% purity). MS[M+H] ⁺ = 779.4

Example 37. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(2-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)ethyl)piperidin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 37)

Step 1. Synthesis of benzyl ((1r,4r)-4-(4-(2-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)ethyl)piperidin-1-yl)cyclohexyl)carbamate (3)

The title compound (420 mg, 635.67 μmol, 28.84% yield, 100% purity, TFA salt) was obtained as a white solid by a similar method to step 4 of Example 22. MS(M+H) ⁺ = 547.5.

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.75 (s, 1H), 9.12 - 8.91 (m, 1H), 7.48 - 7.24 (m, 6H), 6.98 (br d, J = 8.2 Hz, 2H), 6.71 - 6.60 (m, 2H), 5.00 (s, 2H), 3.68 (dd, J = 4.9, 10.8 Hz, 1H), 3.47 - 3.35 (m, 2H), 3.34 - 3.22 (m, 1H), 3.20 - 3.02 (m, 3H), 2.99 - 2.85 (m, 2H), 2.68 - 2.57 (m, 1H), 2.47 - 2.40 (m, 1H), 2.16 - 1.85 (m, 8H), 1.71 - 1.46 (m, 5H), 1.45 - 1.329 (m, 2H), 1.30 - 1.16 (m, 2H).

Step 2. Synthesis of 3-(4-((2-(1-((1r,4r)-4-aminocyclohexyl)piperidin-4-yl)ethyl)amino)phenyl)piperidine-2,6-dione (4)

The title compound (340 mg, crude, TFA salt) was obtained as a yellow oil by a similar method to step 5 of Example 21. MS(M+H) ⁺ = 413.4.

Step 3. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(2-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)ethyl)piperidin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 37)

The title compound as a white solid (184.38 mg, 215.85 μmol, 33.43% yield, 96% purity) and the title compound as a white solid (51 mg, 55.97 μmol, 8.67% yield, 90% purity) were obtained by a similar method to step 6 of Example 21. MS(M+H) ⁺ =820.5.

SFC Method details: "Column: Chiralpak AD-3 50Х4.6mm ID, 3um Mobile phase: Phase A for CO ₂ , and Phase B for IPA+ACN (0.05%DEA); Gradient elution: 60% IPA+ACN (0.05% DEA) in CO ₂ Flow rate: 3mL/min;Detector: PDA Column Temp: 35C;Back Pressure: 100Bar"

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.73 (s, 1H), 8.40 (d, J = 8.8 Hz, 1H), 8.02 (br d, J = 7.9 Hz, 1H), 7.84 (s, 1H), 7.59 (s, 1H), 7.52 - 7.43 (m, 2H), 6.89 (d, J = 8.4 Hz, 2H), 6.50 (d, J = 8.4 Hz, 2H), 5.44 (br t, J = 5.2 Hz, 1H), 4.41 - 4.30 (m, 1H), 4.26 - 4.21 (m, 1H), 3.93 (s, 3H), 3.76 - 3.66 (m, 1H), 3.63 (dd, J = 5.0, 10.4 Hz, 1H), 3.24 (s, 3H), 3.02 - 2.95 (m, 2H), 2.85 - 2.77 (m, 2H), 2.66 - 2.55 (m, 1H), 2.47 - 2.39 (m, 1H), 2.30 - 2.22 (m, 1H), 2.16 (br t, J = 11.1 Hz, 2H), 2.10 - 1.96 (m, 3H), 1.93 - 1.84 (m, 4H), 1.82 - 1.72 (m, 6H), 1.70 - 1.56 (m, 5H), 1.50 - 1.41 (m, 2H), 1.40 - 1.27 (m, 5H), 1.18 - 1.06 (m, 2H), 0.76 (t, J = 7.4 Hz, 3H).

Example 38. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(2-((6-(2,6-dioxopiperidin-3-yl)pyridin-3-yl)amino)ethyl)piperidin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 38)

Step 1. Synthesis of benzyl ((1r,4r)-4-(4-((E)-2-methoxyvinyl)piperidin-1-yl)cyclohexyl)carbamate (2)

To a solution of (methoxymethyl)triphenylphosphonium chloride (1.20 g, 3.50 mmol) in THF (15 mL) was slowly added NaHMDS (1 M, 3.5 mL) at 0 °C, and the mixture was stirred for 8 min under 0 °C CN ₂ . Then, a solution of benzyl ((1r,4r)-4-(4-formylpiperidin-1-yl)cyclohexyl)carbamate (1 g, 2.90 mmol) in THF (10 mL) was slowly added under -78 °C CN ₂ . The mixture was stirred at -78 °C for 60 min. The peak of the desired mass was identified by LCMS. The mixture was warmed to 0 °C and quenched with saturated NH ₄ Cl (10 mL) under 0 °C CN ₂ . The mixture was diluted with saturated NaHCO ₃ solution (20 mL), extracted with MTBE (20 mL x 3), and the combined organic layers were washed with water (10 mL), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure and purified by flash silica gel chromatography (20 g SepaFlash® silica flash column, Eluent of 70–100% EtOAc/Petroleum ether gradient @ 100 mL/min) to afford the title compound (820 mg, 2.20 mmol, 75.82% yield) as a yellow solid. MS(M+H) ⁺ = 373.3.

Step 2. Synthesis of benzyl ((1r,4r)-4-(4-(2-oxoethyl)piperidin-1-yl)cyclohexyl)carbamate (3)

To a solution of benzyl ((1r,4r)-4-(4-((E)-2-methoxyvinyl)piperidin-1-yl)cyclohexyl)carbamate (820 mg, 2.20 mmol) in acetone (16 mL) and H ₂ O (2 mL) was added HCl (12 M, 360 μL), and the mixture was stirred at 15 °C for 1 h. LCMS confirmed the consumption of the starting material and the peak of the desired mass. The mixture was adjusted to approximately pH 8 with saturated NaHCO ₃ solution, extracted with EtOAc (20 mL x 2), and the combined organic layers were washed with water (10 mL), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure to give the title compound (0.8 g, crude) as a yellow solid. MS (M + H) ⁺ = 359.2.

Step 3. Synthesis of benzyl ((1r,4r)-4-(4-(2-((6-(2,6-dioxopiperidin-3-yl)pyridin-3-yl)amino)ethyl)piperidin-1-yl)cyclohexyl)carbamate (5)

The title compound (240 mg, 425.06 μmol, 38.09% yield, 97% purity) was obtained as a yellow solid by a similar method to step 4 of Example 22. MS(M+H) ⁺ =548.3.

Step 4. Synthesis of 3-(5-((2-(1-((1r,4r)-4-aminocyclohexyl)piperidin-4-yl)ethyl)amino)pyridin-2-yl)piperidine-2,6-dione (6)

The title compound (320 mg, crude, TFA salt) as a yellow oil was obtained by a similar method to step 5 of Example 21. MS(M+H) ⁺ = 414.4.

Step 5. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(2-((6-(2,6-dioxopiperidin-3-yl)pyridin-3-yl)amino)ethyl)piperidin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 38)

The title compound (33.6 mg, 37.65 μmol, 6.21% yield, 92% purity) was obtained as a yellow solid by a similar method to step 6 of Example 21. MS(M+H) ⁺ =821.6.

SFC Method details: "Column: (S, S) Whelk-O ₁ 50Х4.6 mm ID, 3.5um mobile phase: Phase A for CO ₂ , and Phase B for IPA+ACN (0.05%DEA); Gradient elution: 60% IPA+ACN (0.05% DEA) in CO ₂ Flow rate: 3mL/min; Detector: PDA Column Temp: 35C; Back Pressure: 100Bar"

¹ H NMR (400 MHz, DMSO- d ₆ ) δ = 10.73 (s, 1H), 8.41 (d, J = 8.9 Hz, 1H), 8.11 - 8.04 (m, 1H), 7.90 - 7.80 (m, 2H), 7.59 (s, 1H), 7.52 - 7.44 (m, 2H), 7.03 (d, J = 8.4 Hz, 1H), 6.92 - 6.86 (m, 1H), 5.76 (br t, J = 4.8 Hz, 1H), 4.42 - 4.31 (m, 1H), 4.23 (dd, J = 3.6, 7.5 Hz, 1H), 3.94 (s, 3H), 3.83 - 3.68 (m, 2H), 3.42 - 3.37 (m, 2H), 3.24 (s, 3H), 3.12 - 2.98 (m, 4H), 2.60 - 2.54 (m, 1H), 2.20 - 1.98 (m, 4H), 1.96 - 1.84 (m, 6H), 1.82 - 1.71 (m, 6H), 1.69 - 1.56 (m, 4H), 1.54 - 1.20 (m, 9H), 0.76 (t, J = 7.4 Hz, 3H)

Example 39. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((5-(2,6-dioxopiperidin-3-yl)pyridin-2-yl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 39)

Step 1. Synthesis of tert-butyl (2',6'-bis(benzyloxy)-[3,3'-bipyridin]-6-yl)carbamate (3)

A solution of 2,6-bis(benzyloxy)-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2 _- yl)pyridine (5 g, 11.98 mmol), tert-butyl (5-bromopyridin-2-yl)carbamate (3.0 g, 10.98 mmol), Pd(dppf)Cl ₂ (800 mg, 1.09 mmol), and Na ₂ CO ₃ (3.81 g, 35.95 mmol) in dioxane (80 mL) and H 2 O (15 mL) was degassed and purged three times with N ₂ , and the mixture was stirred at 110 °C under CN ₂ for 16 h. The peak of the target mass (56%) was identified by LCMS. The reaction mixture was filtered, and the filtrate was diluted with H ₂ O (100 mL) and extracted with EtOAc (300 mL × 2). The combined organic layer was washed with brine (200 mL × 3), dried over anhydrous Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (Biotage; 80 g SepaFlash® silica flash column, eluent of 5–10 % EtOAc:Petroleum ether gradient, 150 mL/min) to give the title compound (2.2 g, 4.55 mmol, 37.97% yield) as a yellow solid. MS (M+ H) ⁺ = 484.3

Step 2. Synthesis of tert-butyl (5-(2,6-dioxopiperidin-3-yl)pyridin-2-yl)carbamate (4)

Solution 1: tert-Butyl (2',6'-bis(benzyloxy)-[3,3'-bipyridin]-6-yl)carbamate (500 mg, 1.03 mmol) in THF (10 mL) and i-PrOH (10 mL). The fixed bed (named FLR ₁ , volume 5 mL) was packed with a granular catalyst (1% Pd/C, WXC1030, 1.7 g). The H ₂ pressure regulator was adjusted to 0.5 MPa, and the flow rate (H ₂ , WuXi-EHS, 30 mL/min). Afterwards, solution 1 was pumped by pump 1 (S ₁ , P1, 0.30 mL/min) and flowed into reactor 1 (FLR ₁ , SS, fixed bed, 6.350 (1/4'') mm, 5 mL, 50 °C; residence time 3.3 min). The reaction mixture was then collected from the reactor. The peak of the target mass was identified by LCMS. The mixture was filtered, and the filter cake was washed with THF (200 mL). The filtrate was concentrated under reduced pressure. The product was triturated with a mixed solvent (DCM: MTBE = 1:5; 30 mL) at 20 °C for 1 h. The mixture was filtered, and the filter cake was dried under reduced pressure to obtain the title compound (160 mg, 524.03 μmol, 50.68% yield) as a pale yellow solid. MS (M+H) ⁺ = 306.2

^1H NMR (400 MHz, DMSO-d ₆ ) δ = 10.88 (s, 1H), 9.67 (s, 1H), 8.11 (d, J = 1.7 Hz, 1H), 7.74 (d, J = 8.6 Hz, 1H), 7.64 - 7.57 (m, 1H), 3.89 - 3.80 (m, 1H), 2.75 - 2.64 (m, 1H), 2.60 - 2.53 (m, 1H), 2.30 - 2.17 (m, 1H), 2.06 - 1.97 (m, 1H), 1.48 (s, 9H).

Step 3. Synthesis of 3-(6-aminopyridin-3-yl)piperidine-2,6-dione (5)

To a solution of tert-butyl (5-(2,6-dioxopiperidin-3-yl)pyridin-2-yl)carbamate (160 mg, 524.03 μmol) in dioxane (4 mL) was added HCl/dioxane (2 M, 15 mL). The mixture was stirred at 20 °C under CN ₂ for 36 h. The peak of the target mass (80%) was confirmed by LCMS. The reaction mixture was concentrated under reduced pressure to obtain the title compound (120 mg, crude, HCl) as a yellow solid. MS (M+H) ⁺ = 206.1

Step 4. Synthesis of benzyl ((1r,4r)-4-(4-(((5-(2,6-dioxopiperidin-3-yl)pyridin-2-yl)amino)methyl)piperidin-1-yl)cyclohexyl)carbamate (7)

To a solution of 3-(6-aminopyridin-3-yl)piperidine-2,6-dione (120 mg, 496.54 μmol, HCl) in DCM (8 mL) and DMF (2 mL) was added benzyl ((1r,4r)-4-(4-formylpiperidin-1-yl)cyclohexyl)carbamate (160 mg, 464.51 μmol) and NaOAc (90 mg, 1.10 mmol). The mixture was stirred at 20 °C for 1 h. Then, NaBH(OAc) ₃ (340 mg, 1.60 mmol) was added at 0 °C, and the mixture was stirred at 20 °C for 15 h. The target mass peak (42%) was identified by LCMS. The reaction mixture was diluted with H ₂ O (10 mL) and DCM (25 mL), and then adjusted to pH = 9 by adding NaHCO ₃ (sat. aq, 20 mL). The mixture was extracted with DCM (25 mL × 2). The combined organic layers were washed with brine (20 mL × 2), dried over anhydrous Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by prep-HPLC (column: Phenomenex Luna C18 150 x 25 mm x10 μm; mobile phase: [H ₂ O (0.1% TFA) - ACN]; gradient: 0% - 25% B over 15.0 min; column Temp: 30 °C). The extract was lyophilized to obtain the title compound benzyl ((1r,4r)-4-(4-(((5-(2,6-dioxopiperidin-3-yl)pyridin-2-yl)amino)methyl)piperidin-1-yl)cyclohexyl)carbamate (120 mg, 224.86 μmol, 45.29% yield) as a pale yellow solid. MS(M+H) ⁺ = 534.4

Step 5. Synthesis of 3-(6-(((1-((1r,4r)-4-aminocyclohexyl)piperidin-4-yl)methyl)amino)pyridin-3-yl)piperidine-2,6-dione (8)

A mixture of benzyl ((1r,4r)-4-(4-(((5-(2,6-dioxopiperidin-3-yl)pyridin-2-yl)amino)methyl)piperidin-1-yl)cyclohexyl)carbamate (80 mg, 149.91 μmol) in TFA (8 mL) was stirred at 50 °C under CN ₂ for 2 h. The main peak of the desired mass was confirmed by LCMS. The reaction mixture was concentrated under reduced pressure to obtain the title compound (76 mg, crude, TFA) as a green oil. MS(M+H) ⁺ = 400.3

Step 6. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((5-(2,6-dioxopiperidin-3-yl)pyridin-2-yl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 39)

The title compound (10.2 mg, 12.22 μmol, 8.38% yield, 95% purity) was obtained as a white solid by a similar method to step 2 of Example 1. MS (M+H) ⁺ = 793.5

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.77 (br s, 1H), 8.50 - 8.32 (m, 1H), 8.08 - 7.94 (m, 1H), 7.91 - 7.81 (m, 1H), 7.77 (d, J = 2.3 Hz, 1H), 7.62 (s, 1H), 7.53 - 7.40 (m, 2H), 7.19 (dd, J = 2.3, 8.7 Hz, 1H), 6.53 - 6.36 (m, 2H), 4.48 - 4.38 (m, 1H), 4.35 - 4.27 (m, 1H), 3.93 (s, 3H), 3.76 - 3.60 (m, 2H), 3.23 (s, 3H), 3.14 - 3.00 (m, 2H), 2.88 - 2.76 (m, 2H), 2.71 - 2.59 (m, 1H), 2.30 - 2.22 (m, 1H), 2.18 - 2.07 (m, 3H), 2.03 - 1.87 (m, 5H), 1.82 - 1.72 (m, 6H), 1.68 - 1.57 (m, 3H), 1.52 - 1.44 (m, 1H), 1.40 - 1.29 (m, 4H), 1.22 (d, J = 6.7 Hz, 5H), 1.15 - 1.07 (m, 2H)

Example 40. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(2-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)ethyl)-[1,4'-bipiperidin]-1'-yl)-3-methoxybenzamide (Compound 40)

To a solution of 3-(4-((2-(piperidin-4-yl)ethyl)amino)phenyl)piperidine-2,6-dione (70 mg, 198.94 μmol, HCl) and MgSO ₄ (118.57 mg, 985.06 μmol) in DMAC (3 mL) was added TEA (99.68 mg, 985.06 μmol, 137.11 μL), followed by (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxy-N-(4-oxopiperidin-1-yl)benzamide (100 mg, 197.01 μmol), and the mixture was stirred at 20 °C for 1 h. NaBH ₃ CN (18.57 mg, 295.52 μmol) was added, and the suspension was stirred at 20°C for 16 h. The peak of the target mass was not confirmed by LCMS. AcOH (118.31 mg, 1.97 mmol, 112.78 μL) was added, and the suspension was stirred at 20-40°C for 48 h. The peak of the target mass (58%) was confirmed by LCMS. The mixture was diluted with H ₂ O (20 mL) and extracted with EtOAc (10 mL x 3). The combined organic layer was washed with brine (20 mL), dried over Na ₂ SO ₄ , filtered, and the filtrate was concentrated under reduced pressure. The residue was purified by prep-HPLC (column: Phenomenex Luna C18 150*25 mm*10 μm; mobile phase: [H ₂ O (0.1% TFA)-ACN]; gradient: 0%-28% B over 15.0 min) and repurified by prep-HPLC (column: Waters xbridge 150*25 mm 10 μm; mobile phase: [H ₂ O (10 mM NH ₄ HCO ₃ )-ACN]; gradient: 30%-60% B over 9.0 min), and the eluate was lyophilized to obtain the title compound (5.0 mg, 6.07 μmol, 3.08% yield, 98% purity) as a white solid. MS(M+H) ⁺ =807.5

^1H NMR (400 MHz, DMSO _- d6 ) δ = 10.75 (s, 1H), 9.26 (s, 1H), 8.42 (d, J = 8.8 Hz, 1H), 7.90 (s, 1H), 7.63 (s, 1H), 7.46 - 7.38 (m, 2H), 6.90 (d, J = 8.5 Hz, 2H), 6.51 (d, J = 8.5 Hz, 2H), 5.50 - 5.42 (m, 1H), 4.42 (t, J = 7.3 Hz, 1H), 4.33 (q, J = 6.6 Hz, 1H), 3.94 (s, 3H), 3.64 (dd, J = 5.0, 10.4 Hz, 1H), 3.24 (s, 3H), 3.06 - 2.96 (m, 4H), 2.91 - 2.84 (m, 2H), 2.83 - 2.74 (m, 2H), 2.66 - 2.55 (m, 2H), 2.48 - 2.40 (m, 2H), 2.29 - 2.19 (m, 1H), 2.14 - 2.07 (m, 2H), 2.04 - 1.98 (m, 2H), 1.94 - 1.90 (m, 1H), 1.83 - 1.75 (m, 5H), 1.73 - 1.65 (m, 3H), 1.63 - 1.56 (m, 3H), 1.51 - 1.44 (m, 2H), 1.41 - 1.33 (m, 1H), 1.23 (d, J = 6.8 Hz, 3H), 1.21 - 1.16 (m, 2H).

Example 41. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(2-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)ethyl)-[1,4'-bipiperidin]-1'-yl)-3-(2-hydroxyethoxy)benzamide (Compound 41)

Step 1. Synthesis of tert-butyl 4-(2-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)ethyl)piperidine-1-carboxylate (3)

The title compound (450 mg, 1.01 mmol, 68.56% yield, 93% purity) was obtained as a yellow solid by a similar method to step 1 of Example 28. MS(M-Boc+H) ⁺ = 316.0

Step 2. Synthesis of 3-(4-((2-(piperidin-4-yl)ethyl)amino)phenyl)piperidine-2,6-dione (4)

The title compound (0.4 g, crude, HCl) was obtained as a brown solid by a similar method to step 2 of Example 28. MS(M+H) ⁺ = 316.2

Step 3. Synthesis of (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-(2-hydroxyethoxy)-N-(1,4-dioxa-8-azaspiro[4.5]decan-8-yl)benzamide (7)

The title compound (110 mg, 189.11 μmol, 17.16% yield) was obtained as a yellow oil by a similar method to step 4 of Example 28. MS(M+H) ⁺ = 582.3

Step 4. Synthesis of (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-(2-hydroxyethoxy)-N-(4-oxopiperidin-1-yl)benzamide (8)

The title compound (180 mg, crude) was obtained as a yellow solid by a similar method to step 5 of Example 28. MS(M+H) ⁺ = 538.3

Step 5. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(2-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)ethyl)-[1,4'-bipiperidin]-1'-yl)-3-(2-hydroxyethoxy)benzamide (Compound 41)

To a solution of (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-(2-hydroxyethoxy)-N-(4-oxopiperidin-1-yl)benzamide (70 mg, 130.21 μmol) and 3-(4-((2-(piperidin-4-yl)ethyl)amino)phenyl)piperidine-2,6-dione (68.72 mg, 195.31 μmol, HCl) in DMAC (5 mL) were added MgSO ₄ (78.36 mg, 651.03 μmol), NaOAc (32.04 mg, 390.62 μmol), and the mixture was stirred at 80 °C for 1 h. NaBH ₃ CN (16.36 mg, 260.41 μmol) was added, and the mixture was stirred at 20°C for 16 h. The peak of the target mass (34%) was confirmed by LCMS. The mixture was diluted with H ₂ O (20 mL) and extracted with EtOAc (10 mL x 3). The combined organic layer was washed with brine (20 mL), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by prep-HPLC (column: Phenomenex Luna C18 150*25 mm*10 μm; mobile phase: [H ₂ O (0.1% TFA) -ACN]; gradient: 0%-25% B over 15.0 min) and repurified by prep-HPLC (column: Waters xbridge 150*25 mm 10 μm; mobile phase: [H ₂ O (10 mM NH ₄ HCO ₃ ) -ACN]; gradient: 28%-58% B over 9.0 min), and the eluate was lyophilized to obtain the title compound (5.5 mg, 6.44 μmol, 4.95% yield, 98% purity) as a white solid. MS(M+H) ⁺ = 837.4

^1H NMR (400 MHz, DMSO _- d6 ) δ = 10.73 (s, 1H), 9.23 (s, 1H), 8.43 (d, J = 8.9 Hz, 1H), 8.06 (s, 1H), 7.90 (s, 1H), 7.43 - 7.38 (m, 2H), 6.90 (d, J = 8.6 Hz, 2H), 6.51 (d, J = 8.6 Hz, 2H), 5.45 (t, J = 5.5 Hz, 1H), 5.18 (t, J = 5.8 Hz, 1H), 4.43 (q, J = 7.9 Hz, 1H), 4.33 (q, J = 7.0 Hz, 1H), 4.11 (t, J = 4.5 Hz, 2H), 3.82 - 3.76 (m, 2H), 3.66 - 3.62 (m, 1H), 3.24 (s, 3H), 3.05 - 2.99 (m, 4H), 2.89 - 2.84 (m, 2H), 2.81 - 2.74 (m, 2H), 2.63 - 2.57 (m, 1H), 2.44 - 2.40 (m, 1H), 2.27 - 2.22 (m, 1H), 2.15 - 2.01 (m, 5H), 1.95 - 1.90 (m, 1H), 1.84 - 1.67 (m, 9H), 1.63 - 1.57 (m, 3H), 1.50 - 1.45 (m, 2H), 1.41 - 1.35 (m, 1H), 1.27 - 1.20 (m, 3H), 1.18 - 1.10 (m, 2H).

Example 42. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(2-((4-((2,6-dioxopiperidin-3-yl)amino)phenyl)amino)ethyl)-[1,4'-bipiperidin]-1'-yl)-3-methoxybenzamide (Compound 42)

Step 1. Synthesis of tert-butyl (4-((2,6-dioxopiperidin-3-yl)amino)phenyl)carbamate (3)

To a solution of tert-butyl (4-aminophenyl)carbamate (3 g, 14.41 mmol) in ACN (20 mL) were added 3-bromopiperidine-2,6-dione (5.53 g, 28.81 mmol), NaHCO ₃ (6.0 g, 71.42 mmol, 2.78 mL), and TBAI (500 mg, 1.35 mmol) at 20 °C, and the mixture was stirred at 80 °C for 16 h. The peak of the target mass (74%) was identified by LCMS. The reaction mixture was filtered, the filter cake was extracted with EtOAc (100 mL), and the filtrate was concentrated under reduced pressure. The product was triturated with a solvent (EtOAc: MTBE = 1:2; 60 mL) at 20 °C for 1 h. The mixture was filtered and the filter cake was dried under reduced pressure to obtain the title compound as a green solid (2.6 g, 8.14 mmol, 56.52% yield). MS(M+H) ⁺ = 320.1

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.79 (s, 1H), 8.95-8.75 (m, 1H), 7.26 - 7.01 (m, 2H), 6.60 (d, J = 8.8 Hz, 2H), 5.86 - 5.23 (m, 1H), 4.32 - 4.16 (m, 1H), 2.79 - 2.67 (m, 1H), 2.62 - 2.53 (m, 1H), 2.16 - 2.04 (m, 1H), 1.90 - 1.77 (m, 1H), 1.44 (s, 9H)

Step 2. Synthesis of 3-((4-aminophenyl)amino)piperidine-2,6-dione (4)

A solution of tert-butyl (4-((2,6-dioxopiperidin-3-yl)amino)phenyl)carbamate (1.1 g, 3.44 mmol) in HCl/dioxane (2 M, 10 mL) was stirred at 20 °C for 14 h. The main peak of the desired mass was identified by LCMS. The mixture was concentrated under reduced pressure to obtain the title compound (1.3 g, crude) as a yellow solid. MS(M+H) ⁺ = 220.1

Step 3. Synthesis of tert-butyl 4-(2-((4-((2,6-dioxopiperidin-3-yl)amino)phenyl)amino)ethyl)piperidine-1-carboxylate (6)

To a solution of 3-((4-aminophenyl)amino)piperidine-2,6-dione (380 mg, 1.49 mmol, HCl) in DCM (10 mL) and DMF (3 mL) were added tert-Butyl 4-(2-oxoethyl)piperidine-1-carboxylate (230 mg, 1.01 mmol) and TEA (828.78 mg, 8.19 mmol, 1.14 mL). The mixture was stirred at 20 °C for 1 h. Then, NaBH(OAc) ₃ (950.00 mg, 4.48 mmol) was added, and the mixture was stirred at 20 °C for 15 h. The major peak of the target mass was identified by LCMS. The reaction mixture was diluted with H ₂ O (10 mL) and DCM (30 mL), and then adjusted to pH = 9 by adding NaHCO ₃ (sat. aq, 30 mL). The suspension was extracted with DCM (30 mL × 2), and the combined organic layer was washed with brine (30 mL × 2), dried over anhydrous Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by prep-HPLC (column: Phenomenex Luna C18 150 x 25 mm x 10 μm; mobile phase: [H ₂ O (0.1% TFA) - ACN]; gradient: 15% - 45% B over 15.0 min; column Temp: 30 °C). The eluate was lyophilized to obtain the title compound (400 mg, 929.07 μmol, 62.52% yield) as a yellow solid. MS(M+H) ⁺ =431.3

Step 4. Synthesis of 3-((4-((2-(piperidin-4-yl)ethyl)amino)phenyl)amino)piperidine-2,6-dione (7)

To a solution of tert-butyl 4-(2-((4-((2,6-dioxopiperidin-3-yl)amino)phenyl)amino)ethyl)piperidine-1-carboxylate (400 mg, 929.07 μmol) in dioxane (5 mL) was added HCl/dioxane (2 M, 25 mL). The mixture was stirred at 20 °C under CN ₂ for 16 h. The peak of the desired mass was identified by LCMS. The reaction mixture was concentrated under reduced pressure to obtain the title compound (340 mg, crude, HCl) as a yellow solid. MS (M+H) ⁺ = 331.2

Step 5. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(2-((4-((2,6-dioxopiperidin-3-yl)amino)phenyl)amino)ethyl)-[1,4'-bipiperidin]-1'-yl)-3-methoxybenzamide (Compound 42)

To a solution of (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxy-N-(4-oxopiperidin-1-yl)benzamide (100 mg, 197.01 μmol) in DMAC (3 mL) was added 3-((4-((2-(piperidin-4-yl)ethyl)amino)phenyl)amino)piperidine-2,6-dione (100 mg, 272.57 μmol, HCl) and TEA (159.48 mg, 1.58 mmol, 219.37 μL). The mixture was stirred at 20 °C for 1 h. After that, NaBH ₃ CN (80 mg, 1.27 mmol) was added at 0 °C, and the suspension was stirred at 20 °C for 15 h. The peak of the target mass (39%) was confirmed by LCMS. The reaction mixture was diluted with H ₂ O (10 mL) and DCM (25 mL), and then NaHCO ₃ (sat. aq, 20 mL) was added to adjust the pH to 9. The mixture was extracted with DCM (25 mL × 2). The mixed organic layer was washed with brine (20 mL × 2), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by prep-HPLC (column: Phenomenex Luna C18 150 x 25 mm x10 μm; mobile phase: [H ₂ O (0.1% TFA) - ACN]; gradient: 0% - 25% B over 15.0 min, column Temp: 30 °C). The eluate was diluted with DCM (10 mL), adjusted to pH = 7~8 by adding NaHCO ₃ (1 M, 10 mL), and extracted with DCM (15 mL × 2). The mixed organic layer was concentrated under reduced pressure and lyophilized to obtain the title compound (48.6 mg, 57.35 μmol, 29.11% yield, 97% purity) as an off-white solid. MS (M+H) ⁺ = 822.6

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.74 (s, 1H), 9.27 (s, 1H), 8.46 - 8.38 (m, 1H), 7.90 (s, 1H), 7.63 (s, 1H), 7.45 - 7.37 (m, 2H), 6.54 (d, J = 8.6 Hz, 2H), 6.45 - 6.39 (m, 2H), 4.99 (d, J = 6.7 Hz, 1H), 4.72 - 4.65 (m, 1H), 4.46 - 4.37 (m, 1H), 4.34 - 4.26 (m, 1H), 4.12 - 4.04 (m, 1H), 3.94 (s, 3H), 3.24 (s, 3H), 3.08 - 2.98 (m, 2H), 2.97 - 2.80 (m, 5H), 2.78 - 2.66 (m, 2H), 2.61 - 2.58 (m, 1H), 2.28 - 2.18 (m, 1H), 2.15 - 2.05 (m, 3H), 2.03 - 1.89 (m, 2H), 1.83 - 1.72 (m, 7H), 1.67 - 1.55 (m, 5H), 1.47 - 1.41 (m, 2H), 1.36 - 1.19 (m, 5H), 1.18 - 1.08 (m, 2H)

Example 43. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(2-((4-((2,6-dioxopiperidin-3-yl)amino)phenyl)amino)ethyl)-[1,4'-bipiperidin]-1'-yl)-3-(2-hydroxyethoxy)benzamide (Compound 43)

To a solution of (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-(2-hydroxyethoxy)-N-(4-oxopiperidin-1-yl)benzamide (150 mg, 279.01 μmol) and 3-((4-((2-(piperidin-4-yl)ethyl)amino)phenyl)amino)piperidine-2,6-dione (81.89 mg, 223.21 μmol, HCl) in DMAC (5 mL) were added TEA (145.40 mg, 1.44 mmol, 200 μL) and MgSO ₄ (167.92 mg, 1.40 mmol), and the mixture was stirred at 20 °C for 1 h. NaBH ₃ CN (26.30 mg, 418.52 μmol) was added, and the mixture was stirred at 20 °C for 16 h, and the main peak of the target mass was confirmed by LCMS. The mixture was diluted with H ₂ O (20 mL) and extracted with EtOAc (10 mL x 3). The combined organic layer was washed with brine (20 mL), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by prep-HPLC (column: Phenomenex Luna C18 150*25 mm*10 um; mobile phase: [H ₂ O (0.1% TFA) -ACN]; gradient: 0%-30% B over 15.0 min), and the eluate was lyophilized. The product was dissolved in H ₂ O (20 mL) and adjusted to pH = 8~9 with NaHCO ₃ . The resulting suspension was extracted with EtOAc (10 mL x 3), and the mixed organic layer was dried over Na ₂ SO ₄ and filtered. The filtrate was concentrated under reduced pressure, and the residue was lyophilized to obtain the title compound (8.2 mg, 8.37 μmol, 3.00% yield, 87% purity) as a brown solid. MS(M+H) ⁺ = 852.6

^1H NMR (400 MHz, DMSO _- d6 ) δ = 10.75 (s, 1H), 9.23 (s, 1H), 8.43 (d, J = 8.9 Hz, 1H), 8.06 (s, 1H), 7.90 (s, 1H), 7.44 - 7.38 (m, 2H), 6.54 (d, J = 8.8 Hz, 2H), 6.42 (d, J = 8.8 Hz, 2H), 5.24 - 5.15 (m, 1H), 5.02 - 4.97 (m, 1H), 4.73 - 4.67 (m, 1H), 4.49 - 4.38 (m, 1H), 4.33 (q, J = 6.5 Hz, 1H), 4.12 - 4.06 (m, 3H), 3.79 (s, 2H), 3.24 (s, 3H), 3.05 - 2.98 (m, 2H), 2.98 - 2.91 (m, 2H), 2.88 - 2.83 (m, 2H), 2.81 - 2.78 (m, 2H), 2.72 - 2.67 (m, 1H), 2.27 - 2.21 (m, 1H), 2.18 - 2.11 (m 3H), 2.04 - 1.98 (m, 1H), 1.96 - 1.91 (m, 1H), 1.83 - 1.73 (m, 7H), 1.70 - 1.52 (m, 8H), 1.46 - 1.42 (m, 2H), 1.23 (d, J = 6.8 Hz, 3H), 1.18 - 1.11 (m, 2H).

Example 44. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(1'-(2-((6-(2,6-dioxopiperidin-3-yl)pyridin-3-yl)amino)ethyl)-[1,4'-bipiperidin]-4-yl)-3-methoxybenzamide (Compound 44)

Step 1. Synthesis of tert-butyl 4-(((benzyloxy)carbonyl)amino)-[1,4'-bipiperidine]-1'-carboxylate (3)

To a solution of tert-butyl 4-oxopiperidine-1-carboxylate (5 g, 25.09 mmol) and benzyl piperidin-4-ylcarbamate (5 g, 21.34 mmol) in DCM (100 mL) was added TEA (6.48 g, 64.02 mmol, 8.91 mL), and the mixture was stirred at 25 °C for 30 min. NaBH(OAc) ₃ (9.05 g, 42.68 mmol) was added at 0 °C, and the mixture was stirred at 25 °C for 14 h. The peak of the desired mass was identified by LCMS. The mixture was diluted with water (50 mL), extracted with EtOAc (10 mL x 2), and the combined organic layer was washed with water (10 mL), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure. The residue was filtered by flash silica gel chromatography (80 g SepaFlash® silica flash column, eluent of 0–10% MeOH/EtOAc gradient @ 200 mL/min) to give the title compound (9 g, 20.69 mmol, 96.96% yield, 96% purity) as a white solid. MS(M+H) ⁺ = 418.3.

Step 2. Synthesis of benzyl (1,4'-bipiperidine)-4-ylcarbamate (4)

To a solution of tert-butyl 4-(((benzyloxy)carbonyl)amino)-[1,4'-bipiperidine]-1'-carboxylate (2 g, 4.79 mmol) in DCM (10 mL) was added HCl/dioxane (2 M, 20 mL), and the mixture was stirred at 15 °C for 4 h. The mixture was concentrated under reduced pressure to obtain benzyl [1,4'-bipiperidin]-4-ylcarbamate (1.7 g, crude, HCl salt) as a white solid. MS(M+H) ⁺ = 318.3.

Step 3. Synthesis of benzyl (1'-(2,2-dimethoxyethyl)-[1,4'-bipiperidin]-4-yl)carbamate (6)

To a solution of benzyl [1,4'-bipiperidin]-4-ylcarbamate (1.7 g, 4.80 mmol, HCl salt) and 2-bromo-1,1-dimethoxyethane (1.62 g, 9.61 mmol, 1.13 mL) in DMF (30 mL) was added K ₂ CO ₃ (1.33 g, 9.61 mmol), and the mixture was stirred at 80 °C for 14 h. 2-Bromo-1,1-dimethoxyethane (1.62 g, 9.61 mmol, 1.13 mL) and K ₂ CO ₃ (1.33 g, 9.61 mmol) were added, and the mixture was stirred at 80 °C for 1 h. The peak of the desired mass was confirmed by LCMS. The mixture was diluted with water (50 mL), extracted with EtOAc (20 mL x 3), and the combined organic layer was washed with brine (10 mL x 2), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (12 g SepaFlash® silica flash column, eluent of 40–60% MeOH/EtOAc gradient @ 100 mL/min) to give the title compound (1 g, 2.47 mmol, 51.33% yield) as a yellow solid. MS(M+H) ⁺ = 406.3

Step 4. Synthesis of 1'-(2,2-dimethoxyethyl)-[1,4'-bipiperidin]-4-amine (7)

A solution of Pd/C (0.3 g, 10% purity) in EtOH (10 mL) was slowly added to a solution of benzyl (1'-(2,2-dimethoxyethyl)-[1,4'-bipiperidin]-4-yl)carbamate (1.00 g, 2.48 mmol) in EtOH (10 mL) under N ₂ , and the mixture was stirred at 40 °C under CH ₂ (45 Psi) for 24 h. LCMS confirmed the consumption of the starting material. The mixture was filtered, and the filter cake was washed with EtOH (80 mL). The filtrate was concentrated under reduced pressure to give the title compound (690 mg, crude) as a yellow oil. MS (M+H) ⁺ = 272.3

Step 5. Synthesis of (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(1'-(2,2-dimethoxyethyl)-[1,4'-bipiperidin]-4-yl)-3-methoxybenzamide (9)

To a solution of (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoic acid (865 mg, 2.03 mmol) and HATU (1.16 g, 3.05 mmol) in DMF (15 mL) was added DIPEA (1.64 g, 12.71 mmol, 2.21 mL), and the mixture was stirred at 15 °C for 15 min. Then, 1'-(2,2-dimethoxyethyl)-[1,4'-bipiperidin]-4-amine (690 mg, 2.54 mmol) was added, and the mixture was stirred at 15 °C for 1 h. The desired mass peak (75%) was confirmed by LCMS. The mixture was diluted with water (10 mL) and saturated NaHCO ₃ solution (20 mL), extracted with EtOAc (20 mL x 3), and the combined organic layer was washed with brine (10 mL x 2), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (5 g SepaFlash® silica flash column, eluent of 30–60% MeOH/EtOAc gradient @ 50 mL/min) to give the title compound (1.14 g, 1.68 mmol, 66.05% yield) as a yellow solid. MS(M+H) ⁺ = 679.4

Step 6. Synthesis of (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxy-N-(1'-(2-oxoethyl)-[1,4'-bipiperidin]-4-yl)benzamide (10)

To _a solution of (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(1'-(2,2-dimethoxyethyl)-[1,4'-bipiperidin]-4-yl)-3-methoxybenzamide (0.1 g, 147.31 μmol) in H 2 O (0.3 mL) was added HBr (149.00 mg, 736.62 μmol, 0.1 mL, 40% purity/water), and the mixture was stirred at 40 °C for 14 h. HBr (745.00 mg, 3.68 mmol, 0.5 mL, 40% purity) was added, and the mixture was stirred at 50 °C for an additional 14 h. The desired mass peak (97%) was confirmed by LCMS. The mixture was slowly added to a saturated NaHCO ₃ solution (20 mL) at 0 °C, and the mixture (pH = 8) was extracted with DCM (10 mL x 2). The combined organic layer was washed with water (5 mL), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure to obtain the title compound (80 mg, crude) as a yellow solid. MS (M + H) ⁺ = 633.5

Step 7. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(1'-(2-((6-(2,6-dioxopiperidin-3-yl)pyridin-3-yl)amino)ethyl)-[1,4'-bipiperidin]-4-yl)-3-methoxybenzamide (Compound 44)

To a solution of 3-(5-aminopyridin-2-yl)piperidine-2,6-dione (469 mg, 1.94 mmol, HCl salt) in DMF (10 mL) was added NaOAc (212.61 mg, 2.59 mmol), followed by AcOH (155.64 mg, 2.59 mmol, 148.37 μL) and a solution of (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxy-N-(1'-(2-oxoethyl)-[1,4'-bipiperidin]-4-yl)benzamide (820 mg, 1.30 mmol) in DCM (10 mL), and the mixture was stirred at 15 °C for 30 min. NaBH(OAc) ₃ (823.92 mg, 3.89 mmol) was added and the mixture was stirred at 15 °C for 2 h. The peak of the desired mass was confirmed by LCMS. The mixture was concentrated under reduced pressure, purified by flash silica gel chromatography (5 g SepaFlash® silica flash column, eluent of 30–50% MeOH/DCM gradient @ 50 mL/min), repurified by prep-HPLC (column: Waters Xbridge C18 150*50 mm* 10 μm; mobile phase: [water (NH ₄ HCO ₃ ) -ACN]; gradient: 25%–55% B over 10 min), and the eluate was lyophilized to obtain the title compound as a white solid (111.17 mg, 129.83 μmol, 10.02% yield, 96% purity). MS(M+H) ⁺ =822.7.

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.73 (s, 1H), 8.44 - 8.39 (m, 1H), 8.05 (br d, J = 7.7 Hz, 1H), 7.88 (d, J = 2.7 Hz, 1H), 7.84 (s, 1H), 7.59 (s, 1H), 7.49 - 7.45 (m, 2H), 7.03 (d, J = 8.4 Hz, 1H), 6.92 (dd, J = 2.7, 8.4 Hz, 1H), 5.61 (t, J = 5.3 Hz, 1H), 4.42 - 4.30 (m, 1H), 4.23 (dd, J = 3.5, 7.6 Hz, 1H), 3.94 (s, 3H), 3.82 - 3.69 (m, 2H), 3.30 - 3.22 (m, 4H), 3.15 - 3.07 (m, 2H), 2.98 - 2.83 (m, 4H), 2.55 - 2.52 (m, 1H), 2.47 - 2.44 (m, 2H), 2.25 - 1.85 (m, 10H), 1.83 - 1.73 (m, 6H), 1.72 - 1.38 (m, 9H), 0.76 (t, J = 7.5 Hz, 3H)

Example 45. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(((5-(2,6-dioxopiperidin-3-yl)pyridin-2-yl)amino)methyl)-[1,4'-bipiperidin]-1'-yl)-3-methoxybenzamide (Compound 45)

To a solution of (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxy-N-(4-oxopiperidin-1-yl)benzamide (130 mg, 256.12 μmol) in DMAC (4 mL) was added 3-(6-((piperidin-4-ylmethyl)amino)pyridin-3-yl)piperidine-2,6-dione (105 mg, 309.89 μmol, HCl) and NaOAc (77.61 mg, 946.10 μmol). The mixture was stirred at 80 °C for 1 h. After that, NaBH(OAc) ₃ (291.04 mg, 1.37 mmol) was added at 20 °C, and the mixture was stirred at 20 °C for 15 h. The peak of the target mass (40%) was confirmed by LCMS. The mixture was diluted with H ₂ O (20 mL) and DCM (40 mL), and then NaHCO ₃ (sat. aq, 50 mL) was added to adjust the pH to 9. The mixture was extracted with DCM (50 mL × 2). The mixed organic layer was dried over Na ₂ SO ₄ , filtered, and the filtrate was concentrated under reduced pressure. The residue was purified by prep-HPLC (column: Phenomenex Luna C18 150 x 25 mm x 10 μm; mobile phase: [H2O (0.1% TFA) - ACN]; gradient: 0% - 25% B over 15.0 min; column Temp: 30 °C) and the eluate was lyophilized. The product was diluted with DCM (15 mL) and adjusted to pH = 7~8 with _NaHCO3 (1 M, 15 mL). Then, the mixture was extracted with DCM (15 mL × 2), and the mixed organic layer was concentrated under reduced pressure and lyophilized to obtain the title compound (50 mg, 61.09 μmol, 23.85% yield, 97% purity) as a white solid. MS (M+H) ⁺ = 794.5

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.77 (s, 1H), 9.25 (s, 1H), 8.45 - 8.37 (m, 1H), 7.93 - 7.86 (m, 1H), 7.77 (d, J = 1.8 Hz, 1H), 7.62 (s, 1H), 7.45 - 7.37 (m, 2H), 7.23 - 7.15 (m, 1H), 6.52 - 6.39 (m, 2H), 4.48 - 4.36 (m, 1H), 4.35 - 4.27 (m, 1H), 3.93 (s, 3H), 3.68 - 3.60 (m, 1H), 3.23 (s, 3H), 3.13 - 2.98 (m, 4H), 2.92 - 2.73 (m, 4H), 2.71 - 2.60 (m, 1H), 2.27 - 2.18 (m, 1H), 2.14 - 1.89 (m, 6H), 1.84 - 1.68 (m, 8H), 1.67 - 1.40 (m, 6H), 1.23 (d, J = 6.6 Hz, 3H), 1.19 - 1.07 (m, 2H)

Example 46. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(2-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)ethyl)piperazin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 46)

To a solution of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxy-N-((1r,4R)-4-(4-(2-oxoethyl)piperazin-1-yl)cyclohexyl)benzamide (90.00 mg, 145.45 μmol) in DCM (4 mL) and DMF (1 mL) was added 3-(4-aminophenyl)piperidine-2,6-dione (52 mg, 254.62 μmol) and HOAc (8.73 mg, 145.45 μmol, 8.33 μL). The mixture was stirred at 20 °C for 1 h. After that, NaBH(OAc) ₃ (123.31 mg, 581.80 μmol), HOAc (8.73 mg, 145.45 μmol, 8.33 μL) were added at 0 °C, and the mixture was stirred at 20 °C for 15 h. The peak of the target mass was confirmed by LCMS. The reaction mixture was diluted with H ₂ O (15 mL) and DCM (20 mL), and then adjusted to pH = 9 by adding NaHCO ₃ (sat. aq, 20 mL). The mixture was extracted with DCM (30 mL × 2). The mixed organic layer was washed with brine (30 mL × 2), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by prep-HPLC (column: Phenomenex Luna C18 150 x 25 mm x10 μm; mobile phase: [H ₂ O (0.1% TFA) - ACN]; gradient: 0% - 25% B over 15.0 min, column Temp: 30 °C) and repurified by prep-HPLC (column: Waters xbridge 150 x 25 mm 10 μm; mobile phase: [H ₂ O (10 mM NH ₄ HCO ₃ ) - ACN]; gradient: 30% - 60% B over 15.0 min, column Temp: 30 °C) and the eluate was lyophilized to obtain the title compound (1.3 mg, 1.59 μmol, 1.10% yield, 99% purity) as a white solid. MS(M+H) ⁺ = 807.5

¹ H NMR (400 MHz, DMSO- d ₆ ) δ = 10.75 (s, 1H), 8.47 - 8.38 (m, 1H), 8.09 - 7.98 (m, 1H), 7.90 (s, 1H), 7.66 - 7.60 (m, 1H), 7.50 - 7.45 (m, 2H), 6.96 - 6.88 (m, 2H), 6.54 (d, J = 8.4 Hz, 2H), 5.36 - 5.27 (m, 1H), 4.47 - 4.39 (m, 1H), 4.36 - 4.29 (m, 1H), 3.94 (s, 3H), 3.77 - 3.70 (m, 1H), 3.67 - 3.61 (m, 1H), 3.32 - 3.30 (m, 2H), 3.24 (s, 3H), 3.14 - 3.06 (m, 2H), 2.48 - 2.41 (m, 8H), 2.28 - 2.18 (m, 2H), 2.05 - 1.95 (m, 3H), 1.94 - 1.71 (m, 10H), 1.66 - 1.59 (m, 2H), 1.40 - 1.29 (m, 4H), 1.23 (d, J = 6.7 Hz, 3H)

Example 47. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(2-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)ethyl)piperazin-1-yl)cyclohexyl)-3-(2-hydroxyethoxy)benzamide (Compound 47)

Step 1. Synthesis of benzyl 4-((1r,4r)-4-aminocyclohexyl)piperazine-1-carboxylate (2)

A mixture of benzyl 4-((1r,4r)-4-((tert-butoxycarbonyl)amino)cyclohexyl)piperazine-1-carboxylate (1 g, 2.39 mmol) in HCl/dioxane (2 M, 10 mL) was stirred at 20 °C for 2 h. The main peak of the desired mass was identified by LCMS, and the mixture was concentrated under reduced pressure to obtain the title compound (0.9 g, crude, HCl) as a yellow solid. MS (M+H) ⁺ = 318.1

Step 2. Synthesis of benzyl 4-((1R,4r)-4-(4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-(2-hydroxyethoxy)benzamido)cyclohexyl)piperazine-1-carboxylate (4)

To a solution of benzyl 4-((1r,4r)-4-aminocyclohexyl)piperazine-1-carboxylate (0.5 g, 1.41 mmol, HCl) and (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-(2-hydroxyethoxy)benzoic acid (600 mg, 1.36 mmol) in DMF (10 mL) were added HATU (644.67 mg, 1.70 mmol) and DIPEA (547.81 mg, 4.24 mmol, 738.29 μL), and the mixture was stirred at 20 °C for 14 h. The peak of the target mass (30%) was identified by LCMS. The mixture was filtered and the filtrate was purified by prep-HPLC (column: Phenomenex luna C18 150*25 mm*10 um; mobile phase: [H ₂ O (0.225% FA)-ACN]; gradient: 15%-45% B over 15.0 min) to obtain the title compound (350 mg, 425.17 μmol, 30.09% yield, 90% purity) as a yellow solid. MS (M+H) ⁺ = 741.4

Step 3. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-(2-hydroxyethoxy)-N-((1r,4R)-4-(piperazin-1-yl)cyclohexyl)benzamide (5)

A solution of benzyl 4-((1R,4r)-4-(4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-(2-hydroxyethoxy)benzamido)cyclohexyl)piperazine-1-carboxylate (350 mg, 472.41 μmol) in TFA (4.61 g, 40.39 mmol, 3 mL) was stirred at 50 °C for 2 h. The major peak of the desired mass was confirmed by LCMS (M+TFA). The mixture was concentrated under reduced pressure, and the residue was dissolved in _H2O (20 mL) and pH=10~11 with LiOH. The resulting mixture was stirred at 20°C for 1 hour, and the resulting suspension was concentrated under reduced pressure to obtain the title compound (330 mg, crude) as a yellow solid. MS(M+H) ⁺ =607.4

Step 4. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(2,2-dimethoxyethyl)piperazin-1-yl)cyclohexyl)-3-(2-hydroxyethoxy)benzamide (6)

To a solution of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-(2-hydroxyethoxy)-N-((1r,4R)-4-(piperazin-1-yl)cyclohexyl)benzamide (270 mg, 444.99 μmol) and 2-bromo-1,1-dimethoxy-ethane (150.42 mg, 889.98 μmol, 104.46 μL) in DMF (3 mL) was added LiOH·H ₂ O (18.67 mg, 444.99 μmol), and the resulting mixture was stirred at 60 °C for 33 h. The peak of the target mass (80%) was confirmed by LCMS. The mixture was diluted with water (20 mL) and extracted with EtOAc (20 mL x 3). The combined organic layer was washed with brine (50 mL), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure to obtain the title compound (0.4 g, crude) as a yellow solid. MS (M+H) ⁺ = 695.4

Step 5. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-(2-hydroxyethoxy)-N-((1r,4R)-4-(4-(2-oxoethyl)piperazin-1-yl)cyclohexyl)benzamide (7)

A mixture of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(2,2-dimethoxyethyl)piperazin-1-yl)cyclohexyl)-3-(2-hydroxyethoxy)benzamide (0.3 g, 431.74 μmol) in HBr (7.45 g, 36.83 mmol, 5 mL, 40% purity) was stirred at 50 °C for 4 h. The peak of the desired mass was identified by LCMS. The mixture was concentrated under reduced pressure to give the title compound (0.2 g, 274.08 μmol, 63.48% yield, HBr salt) as a yellow oil. MS (M+H) ⁺ =649.3

Step 6. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(2-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)ethyl)piperazin-1-yl)cyclohexyl)-3-(2-hydroxyethoxy)benzamide (Compound 47)

To a solution of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-(2-hydroxyethoxy)-N-((1r,4R)-4-(4-(2-oxoethyl)piperazin-1-yl)cyclohexyl)benzamide (100 mg, 154.13 μmol, HBr) and 3-(4-aminophenyl)piperidine-2, 6-dione (31.48 mg, 154.13 μmol) in DMF (2 mL) and DCM (2 mL) was added AcOH (9.26 mg, 154.13 μmol, 8.82 μL), and the mixture was stirred at 20 °C for 0.5 h. NaBH(OAc) ₃ (65.33 mg, 308.26 μmol) was added, and the mixture was stirred at 20°C for 0.5 h. The peak of the target mass (21%) was confirmed by LCMS. The mixture was diluted with H ₂ O (20 mL) and extracted with EtOAc (10 mL x 3). The combined organic layer was washed with brine (20 mL), dried over Na ₂ SO ₄ , filtered, and the filtrate was concentrated under reduced pressure. The residue was purified by prep-HPLC (column: Phenomenex Luna C18 150*25 mm*10 um; mobile phase: [H ₂ O (0.1% TFA)-ACN]; gradient: 0%-30% B over 15.0 min) and repurified by prep-HPLC (column: Waters xbridge 150*25 mm 10 um; mobile phase: [H ₂ O (10mM NH ₄ HCO ₃ )-ACN]; gradient: 25%-55% B over 9.0 min), and the eluate was lyophilized. The title compound was obtained as a white solid (3.9 mg, 4.29 μmol, 2.78% yield, 92% purity). MS(M+H) ⁺ =837.5

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.73 (s, 1H), 8.47 - 8.34 (m, 1H), 8.10 - 7.98 (m, 2H), 7.90 (s, 1H), 7.52 - 7.42 (m, 2H), 6.91 (d, J = 8.4 Hz, 2H), 6.54 (d, J = 8.6 Hz, 2H), 5.31 (t, J = 5.6 Hz, 1H), 5.21 - 5.15 (m, 1H), 4.49 - 4.39 (m, 1H), 4.36 - 4.29 (m, 1H), 4.12 (t, J = 4.7 Hz, 2H), 3.83 - 3.77 (m, 2H), 3.69 - 3.63 (m, 2H), 3.54 - 3.46 (m, 3H), 3.24 (s, 3H), 3.14 - 3.06 (m, 3H), 2.46 - 3.41 (m, 5H), 2.28 - 2.14 (m, 2H), 2.13 - 1.96 (m, 4H), 1.95 - 1.74 (m, 10H), 1.65 - 1.56 (m, 2H), 1.40 - 1.28 (m, 4H), 1.23 (d, J = 6.8 Hz, 3H).

Example 48. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(2-((4-((2,6-dioxopiperidin-3-yl)amino)phenyl)amino)ethyl)piperazin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 48)

Step 1. Synthesis of benzyl 4-((1r,4r)-4-aminocyclohexyl)piperazine-1-carboxylate (2)

To a solution of benzyl 4-((1r,4r)-4-((tert-butoxycarbonyl)amino)cyclohexyl)piperazine-1-carboxylate (1.0 g, 2.39 mmol) in dioxane (4 mL) was added HCl/dioxane (2 M, 30 mL) at 20 °C, and the mixture was stirred at 20 °C for 2 h. The peak of the desired mass was identified by LCMS. The reaction mixture was concentrated under reduced pressure to obtain the title compound (840 mg, crude, HCl) as a white solid. MS(M+H) ⁺ = 318.2

Step 2. Synthesis of benzyl 4-((1R,4r)-4-(4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzamido)cyclohexyl)piperazine-1-carboxylate (4)

The title compound (1.2 g, 1.69 mmol, 86.82% yield) was obtained as a pale yellow solid by a similar method to step 2 of Example 47. MS(M+H) ⁺ = 711.5

Step 3. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxy-N-((1r,4R)-4-(piperazin-1-yl)cyclohexyl)benzamide (5)

The title compound (485 mg, crude, TFA) was obtained as a yellow oil by a similar method to step 3 of Example 47. MS(M+H) ⁺ = 577.4

Step 4. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(2,2-dimethoxyethyl)piperazin-1-yl)cyclohexyl)-3-methoxybenzamide (6)

To a solution of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxy-N-((1r,4R)-4-(piperazin-1-yl)cyclohexyl)benzamide (480 mg, 694.89 μmol, TFA) in DMF (20 mL) were added 2-bromo-1,1-dimethoxyethane (240 mg, 1.42 mmol, 166.67 μL) and K ₂ CO ₃ (300 mg, 2.17 mmol) at 20 °C, and the mixture was stirred at 70 °C for 32 h. The peak of the target mass (87%) was confirmed by LCMS. The reaction mixture was diluted with H ₂ O (15 mL) and extracted with EtOAc (40 mL × 2). The combined organic layer was washed with NaHCO ₃ (aq, 30 mL) and brine (30 mL × 2), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (Biotage; 12 g SepaFlash® silica flash column, eluent of 0–15 % MeOH:DCM 120 mL/min) to give the title compound (400 mg, 601.65 μmol, 86.58% yield) as a pale yellow solid. MS (M+H) ⁺ = 665.4

Step 5. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxy-N-((1r,4R)-4-(4-(2-oxoethyl)piperazin-1-yl)cyclohexyl)benzamide (7)

The title compound (300 mg, crude, HBr) was obtained as a pale yellow oil by a similar method to step 6 of Example 44. MS(M+H ₂ O+H) ⁺ = 637.5

Step 6. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(2-((4-((2,6-dioxopiperidin-3-yl)amino)phenyl)amino)ethyl)piperazin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 48)

To a solution of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxy-N-((1r,4R)-4-(4-(2-oxoethyl)piperazin-1-yl)cyclohexyl)benzamide (300 mg, 428.77 μmol HBr) in DCM (10 mL) and DMF (4 mL) were added 3-((4-aminophenyl)amino)piperidine-2,6-dione (200 mg, 782.17 μmol, HCl) and NaOAc (300 mg, 3.66 mmol). The mixture was stirred at 20 °C for 1 h. Afterwards, NaBH(OAc) ₃ (400 mg, 1.89 mmol) was added at 0 °C and the mixture was stirred at 20 °C for 15 h. By LCMS The target mass peak (35%) was identified. The reaction mixture was diluted with H ₂ O (20 mL) and DCM (40 mL), and then adjusted to pH = 9 by adding NaHCO ₃ (sat. aq, 40 mL). The mixture was extracted with DCM (50 mL × 2), and the combined organic layer was washed with brine (50 mL × 2), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by prep-HPLC (column: Phenomenex Luna C18 150 x 25 mm x 10 μm; mobile phase: [H ₂ O (0.1% TFA) - ACN]; gradient: 0% - 25% B over 15.0 min, column Temp: 30 °C). The eluate was diluted with DCM (10 mL), and then NaHCO ₃ (1 M, 10 mL) was added to adjust the pH to 7–8. The mixture was extracted with DCM (15 mL × 2), and the combined organic layer was concentrated under reduced pressure and lyophilized to obtain the title compound (18.7 mg, 21.84 μmol, 5.09% yield, 96% purity) as an off-white solid. MS (M+H) ⁺ = 822.5

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.74 (s, 1H), 8.46 - 8.37 (m, 1H), 8.10 - 8.02 (m, 1H), 7.90 (s, 1H), 7.63 (s, 1H), 7.51 - 7.44 (m, 2H), 6.58 - 6.51 (m, 2H), 6.45 (d, J = 8.8 Hz, 2H), 5.04 (d, J = 6.8 Hz, 1H), 4.59 - 4.52(m, 1H), 4.46 - 4.38 (m, 1H), 4.33 (q, J = 6.8 Hz, 1H), 4.14 - 4.06 (m, 1H), 3.95 (s, 3H), 3.79 - 3.66 (m, 1H), 3.24 (s, 3H), 3.07 - 2.97 (m, 2H), 2.76 - 2.63 (m, 2H), 2.49 - 2.30 (m, 8H), 2.26 - 2.19 (m, 1H), 2.16 - 2.08 (m, 1H), 2.06 - 1.96 (m, 2H), 1.95 - 1.71 (m, 11H), 1.66 - 1.57 (m, 2H), 1.41 - 1.28 (m, 4H), 1.23 (d, J) = 6.7 Hz, 3H)

Example 49. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(2-((3-(2,4-dioxotetrahydropyrimidin-1(2H)-yl)-1-methyl-1H-indazol-6-yl)amino)ethyl)piperazin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 49)

Step 1. Synthesis of 1-(6-((2-((tert-butyldimethylsilyl)oxy)ethyl)amino)-1-methyl-1H-indazol-3-yl)dihydropyrimidine-2,4(1H,3H)-dione (2)

To a solution of 1-(6-amino-1-methyl-1H-indazol-3-yl)dihydropyrimidine-2,4(1H,3H)-dione (360 mg, 1.39 mmol) in DCM (6 mL) were added AcOH (83 mg, 1.39 mmol) and 2-((tert-butyldimethylsilyl)oxy)acetaldehyde (220 mg, 1.26 mmol). The mixture was stirred at 25 °C for 30 min. Then, NaBH(OAc) ₃ (736 mg, 3.47 mmol) was added, and the mixture was stirred at 25 °C for 14 h. The desired mass peak (56%) was confirmed by LCMS. The reaction mixture was diluted with water (20 mL), adjusted to pH=9 with saturated NaHCO ₃ , extracted with DCM (50 mL X 3), and the combined organic layer was washed with brine (20 mL X 3), dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (12 g SepaFlash® silica flash column, Eluent of 90–100% EtOAc/Petroleum ether gradient @ 60 mL/min) to give the title compound (300 mg, 718.43 μmol, 51.74% yield) as a brown solid. MS(M+H) ⁺ =418.2.

Step 2. Synthesis of 1-(6-((2-hydroxyethyl)amino)-1-methyl-1H-indazol-3-yl)dihydropyrimidine-2,4(1H,3H)-dione (3)

To a solution of 1-(6-((2-((tert-butyldimethylsilyl)oxy)ethyl)amino)-1-methyl-1H-indazol-3-yl)dihydropyrimidine-2,4(1H,3H)-dione (270 mg, 646.59 μmol) in THF (3 mL) was added TBAF (1 M, 1.3 mL). The mixture was stirred at 25 °C for 2 h. The desired mass peak (87%) was identified by LCMS. The reaction mixture was diluted with water (20 mL), adjusted to pH=9 with saturated NaHCO ₃ , and extracted with DCM (30 mL X 5). The combined organic layer was washed with brine (20 mL X 2), dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (20 g SepaFlash® silica flash column, eluent of 10–20% MeOH/EtOAc 40 mL/min) to give the title compound (100 mg, 329.69 μmol, 50.99% yield) as a brown oil. MS(M+H) ⁺ = 304.2.

Step 3. Synthesis of 1-(6-((2-bromoethyl)amino)-1-methyl-1H-indazol-3-yl)dihydropyrimidine-2,4(1H,3H)-dione (4)

To a solution of DDQ (45 mg, 197.81 μmol), PPh ₃ (52 mg, 197.81 μmol), and tetraethylammonium bromide (64 mg, 197.81 μmol) in DCM (4 mL) was added 1-(6-((2-hydroxyethyl)amino)-1-methyl-1H-indazol-3-yl)dihydropyrimidine-2,4(1H,3H)-dione (50 mg, 164.84 μmol), and the mixture was stirred at 22°C for 4 h. The desired mass peak (49%) was confirmed by LCMS. The mixture was concentrated under reduced pressure. The residue was purified by Prep-TLC (EtOAc:MeOH=30:1) to obtain the title compound as a green solid (60 mg, 93.39 μmol, 56.65% yield, 57% purity). MS(M+H) ⁺ =366.0.

Step 4. Synthesis of tert-butyl ((1r,4r)-4-(4-(2-((3-(2,4-dioxotetrahydropyrimidin-1(2H)-yl)-1-methyl-1H-indazol-6-yl)amino)ethyl)piperazin-1-yl)cyclohexyl)carbamate (6)

To a solution of 1-(6-((2-bromoethyl)amino)-1-methyl-1H-indazol-3-yl)dihydropyrimidine-2,4(1H,3H)-dione (60 mg, 93.39 μmol, 57% purity) and tert-butyl N-(4-piperazin-1-ylcyclohexyl)carbamate (40 mg, 140.08 μmol) in DMF (5 mL) were added DIPEA (36 mg, 280.17 μmol) and NaI (21 mg, 140.08 μmol). The mixture was stirred at 60 °C for 16 h. The desired mass peak (31%) was identified by LCMS. The reaction mixture was diluted with water (20 mL), adjusted to pH=9 with saturated NaHCO ₃ , and extracted with EtOAc (30 mL X 3 ). The combined organic layer was washed with brine (20 mL X 2), dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure. The residue was purified by prep-TLC (MeOH) to give the title compound (30 mg, 52.22 μmol, 55.92% yield, 99% purity) as a white solid. MS(M+H) ⁺ =569.4.

Step 5. Synthesis of 1-(6-((2-(4-((1r,4r)-4-aminocyclohexyl)piperazin-1-yl)ethyl)amino)-1-methyl-1H-indazol-3-yl)dihydropyrimidine-2,4(1H,3H)-dione (7)

To a solution of tert-butyl ((1r,4r)-4-(4-(2-((3-(2,4-dioxotetrahydropyrimidin-1(2H)-yl)-1-methyl-1H-indazol-6-yl)amino)ethyl)piperazin-1-yl)cyclohexyl)carbamate (30 mg, 52.75 μmol) in DCM (2 mL) was added TFA (0.5 mL), and the mixture was stirred at 20 °C for 1 h. The major peak of the desired mass was identified by LCMS. The mixture was concentrated under reduced pressure to give the title compound (31 mg, 52.74 μmol, 100.00% yield, TFA) as a brown oil. The product was used directly without further purification. MS(M+H) ⁺ = 469.4.

Step 6. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(2-((3-(2,4-dioxotetrahydropyrimidin-1(2H)-yl)-1-methyl-1H-indazol-6-yl)amino)ethyl)piperazin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 49)

To a mixture of (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoic acid (20 mg, 47.47 μmol) in DMF (2 mL) were added TEA (16 mg, 158.23 μmol) and HATU (18 mg, 47.47 μmol), and the mixture was stirred at 20°C for 1 h. Afterwards, 1-(6-((2-(4-((1r,4r)-4-aminocyclohexyl)piperazin-1-yl)ethyl)amino)-1-methyl-1H-indazol-3-yl)dihydropyrimidine-2,4(1H,3H)-dione (31 mg, 52.74 μmol, TFA) was added and the mixture was stirred at 20 °C for 14 h. The peak of the desired mass (78%) was confirmed by LCMS. The reaction mixture was diluted with water (50 mL), adjusted to pH=9 with saturated NaHCO ₃ , and extracted with EtOAc (20 mL X 3). The mixed organic layer was washed with brine (10 mL X 2), dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure. The residue was purified by prep-TLC (MeOH) to give the title compound as an off-white solid (23.6 mg, 24.92 μmol, 47.24% yield, 92.5% purity). MS(M+H) ⁺ =876.5.

¹ H NMR (400 MHz, DMSO- d ₆ ) δ = 10.47 (s, 1H), 8.44 - 8.37 (m, 1H), 8.11 - 8.02 (m, 1H), 7.84 (s, 1H), 7.60 (s, 1H), 7.49 - 7.44 (m, 2H), 7.33 - 7.26 (m, 1H), 6.59 - 6.50 (m, 1H), 6.45 - 6.30 (m, 1H), 5.88 - 5.68 (m, 1H), 4.43 - 4.29 (m, 1H), 4.28 - 4.20 (m, 1H), 3.94 (s, 3H), 3.86 (t, J = 6.8 Hz, 2H), 3.82 (s, 3H), 3.78 - 3.70 (m, 1H), 3.42 - 3.35 (m, 2H), 3.27 - 3.17 (m, 5H), 2.72 (t, J = 6.8 Hz, 2H), 2.63 - 2.56 (m, 3H), 2.09 - 1.97 (m, 2H), 1.97 - 1.85 (m, 5H), 1.85 - 1.69 (m, 5H), 1.68 - 1.58 (m, 3H), 1.47 - 1.30 (m, 4H), 1.30 - 1.13 (m, 4H), 0.91 - 0.80 (m, 1H), 0.76 (t, J = 7.6 Hz, 3H).

Example 50. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-((4-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)piperidin-1-yl)methyl)cyclohexyl)-3-methoxybenzamide (Compound 50)

Step 1. Synthesis of tert-butyl 4-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)piperidine-1-carboxylate (3)

To a solution of 3-(4-aminophenyl)piperidine-2,6-dione (300 mg, 1.47 mmol) in DCM (10 mL) and DMF (2 mL) were added tert-Butyl 4-oxopiperidine-1-carboxylate (400 mg, 2.01 mmol) and TEA (581.60 mg, 5.75 mmol, 800 μL). The mixture was stirred at 20 °C for 1 h. Then, NaBH(OAc) ₃ (1 g, 4.72 mmol) was added to the mixture at 0 °C, and the mixture was stirred at 20 °C for 15 h. The target mass peak (61%) was confirmed by LCMS. H ₂ O (15 mL) was added to the reaction mixture, diluted with DCM (20 mL), and adjusted to pH = 9 by adding NaHCO ₃ (sat. aq, 20 mL). The mixture was extracted with DCM (30 mL × 2), and the combined organic layer was washed with brine (30 mL × 2), dried over Na ₂ SO ₄ , filtered, and the filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (10 g SepaFlash® silica flash column, Eluent of 30–50% EtOAc: Petroleum ether gradient, 100 mL/min) to give the title compound (550 mg, 1.42 mmol, 96.63% yield) as a pale yellow solid. MS (M + Na) ⁺ = 410.2

Step 2. Synthesis of 3-(4-(piperidin-4-ylamino)phenyl)piperidine-2,6-dione (4)

To a solution of tert-butyl 4-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)piperidine-1-carboxylate (550 mg, 1.42 mmol) in dioxane (3 mL) was added HCl/dioxane (2 M, 9.82 mL). The mixture was stirred at 20 °C under N ₂ for 16 h. The peak of the desired mass was identified by LCMS. The reaction mixture was concentrated under reduced pressure to obtain the title compound (460 mg, crude, HCl) as a white solid. MS(M+H) ⁺ = 288.2

Step 3. Synthesis of tert-butyl ((1r,4r)-4-((4-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)piperidin-1-yl)methyl)cyclohexyl)carbamate (5)

To a solution of 3-(4-(piperidin-4-ylamino)phenyl)piperidine-2,6-dione (150 mg, 463.22 μmol, HCl) in DCM (4 mL) and DMF (2 mL) were added tert-butyl ((1r,4r)-4-formylcyclohexyl)carbamate (106 mg, 466.35 μmol) and TEA (283.53 mg, 2.80 mmol, 390.00 μL). The mixture was stirred at 20 °C for 1 h. Then, NaBH(OAc) ₃ (550 mg, 2.60 mmol) was added to the mixture at 0 °C, and the mixture was stirred at 20 °C for 15 h. The peak of the target mass (67%) was confirmed by LCMS. H ₂ O (15 mL) was added to the reaction mixture, diluted with DCM (20 mL), and adjusted to pH = 9 with NaHCO ₃ (sat. aq, 320 mL). The mixture was extracted with DCM (30 mL × 2), and the mixed organic layer was washed with brine (30 mL × 2), dried over Na ₂ SO ₄ , filtered, and the filtrate was concentrated under reduced pressure to obtain a residue. The residue was triturated with a solvent (DCM: MTBE = 1:5; 12 mL) at 20 ^o C for 1 h, the mixture was filtered, and the filter cake was dried under reduced pressure to obtain the title compound (150 mg, 300.81 μmol, 64.94% yield) as a white solid. MS (M + H) ⁺ = 499.4

Step 4. Synthesis of 3-(4-((1-(((1r,4r)-4-aminocyclohexyl)methyl)piperidin-4-yl)amino)phenyl)piperidine-2,6-dione (6)

To a solution of tert-butyl ((1r,4r)-4-((4-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)piperidin-1-yl)methyl)cyclohexyl)carbamate (120 mg, 240.65 μmol) in dioxane (4 mL) was added HCl/dioxane (2 M, 10 mL). The mixture was stirred at 20 °C under N ₂ for 16 h. The main peak of the desired mass was identified by LCMS. The reaction mixture was concentrated under reduced pressure to obtain the title compound (80 mg, crude, HCl) as a yellow solid. MS(M+H) ⁺ = 399.3

Step 5. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-((4-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)piperidin-1-yl)methyl)cyclohexyl)-3-methoxybenzamide (Compound 50)

The title compound (77.6 mg, 97.00 μmol, 49.89% yield, 99% purity) was obtained as a white solid by a similar method to step 6 of Example 39. MS(M+H) ⁺ = 792.4

^1H NMR (400 MHz, DMSO-d ₆ ) δ = 10.72 (s, 1H), 8.45 - 8.38 (m, 1H), 8.09 - 8.02 (m, 1H), 7.89 (s, 1H), 7.62 (s, 1H), 7.52 - 7.44 (m, 2H), 6.88 (d, J = 8.2 Hz, 2H), 6.52 (d, J = 8.3 Hz, 2H), 5.39 - 5.32 (m, 1H), 4.48 - 4.37 (m, 1H), 4.35 - 4.25 (m, 1H), 3.94 (s, 3H), 3.80 - 3.68 (m, 1H), 3.67 - 3.58 (m, 1H), 3.23 (s, 3H), 3.18 - 3.08 (m, 1H), 2.83 - 2.72 (m, 2H), 2.68 - 2.54 (m, 1H), 2.49 - 2.40 (m, 2H), 2.14 - 2.03 (m, 3H), 2.03 - 1.94 (m, 4H), 1.90 - 1.73 (m, 10H), 1.67 - 1.56 (m, 2H), 1.48 - 1.29 (m, 5H), 1.23 (d, J = 6.7 Hz, 3H), 1.01 - 0.86 (m, 2H)

Example 51. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-((4-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)piperidin-1-yl)methyl)piperidin-1-yl)-3-methoxybenzamide (Compound 51)

Step 1. Synthesis of tert-butyl (4-((4-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)piperidin-1-yl)methyl)piperidin-1-yl)carbamate (3)

The title compound (200 mg, 400.29 μmol, 86.41% yield) was obtained as a yellow solid by a similar method to step 3 of Example 50. MS(M+ H) ⁺ = 500.4

Step 2. Synthesis of 3-(4-((1-((1-aminopiperidin-4-yl)methyl)piperidin-4-yl)amino)phenyl)piperidine-2,6-dione (4)

To a solution of tert-butyl (4-((4-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)piperidin-1-yl)methyl)piperidin-1-yl)carbamate (200 mg, 400.29 μmol) in DCM (2 mL) was added TFA (3 mL) at 0 °C. The mixture was stirred at 20 °C under CN ₂ for 2 h. The main peak of the desired mass was identified by LCMS. The reaction mixture was concentrated under reduced pressure to obtain the title compound (200 mg, crude, TFA) as a yellow oil. MS(M+H) ⁺ = 400.3

Step 3. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-((4-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)piperidin-1-yl)methyl)piperidin-1-yl)-3-methoxybenzamide (Compound 51)

The title compound (30.4 mg, 37.95 μmol, 19.52% yield, 99% purity) was obtained as a white solid by a similar method to step 5 of Example 50. MS(M+H) ⁺ = 793.5

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.73 (s, 1H), 9.27 (s, 1H), 8.46 - 8.38 (m, 1H), 7.90 (s, 1H), 7.63 (s, 1H), 7.47 - 7.38 (m, 2H), 6.89 (d, J = 8.4 Hz, 2H), 6.53 (d, J = 8.6 Hz, 2H), 5.41 - 5.32 (m, 1H), 4.48 - 4.38 (m, 1H), 4.37 - 4.28 (m, 1H), 3.94 (s, 3H), 3.68 - 3.59 (m, 1H), 3.24 (s, 3H), 3.19 - 3.12 (m, 1H), 3.03 - 2.97 (m, 2H), 2.84 - 2.73 (m, 4H), 2.65 - 2.60 (m, 1H), 2.46 - 2.40 (m, 1H), 2.20 - 2.12 (m, 2H), 2.09 - 1.97 (m, 5H), 1.94 - 1.85 (m, 3H), 1.83 - 1.71 (m, 6H), 1.67 - 1.57 (m, 2H), 1.53 - 1.45 (m, 1H), 1.42 - 1.33 (m, 2H), 1.28 - 1.20 (m, 5H)

Example 52. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-((4-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)piperazin-1-yl)methyl)cyclohexyl)-3-methoxybenzamide (Compound 52)

Step 1. Synthesis of benzyl 4-((tert-butoxycarbonyl)amino)piperazine-1-carboxylate (2)

To a solution of benzyl piperazine-1-carboxylate (8 g, 36.32 mmol, 7.01 mL) in H ₂ O (100 mL) were added NaOH (8.72 g, 217.92 mmol) and (aminooxy)sulfonic acid (6.22 g, 55.03 mmol) at 0 °C. The mixture was stirred at 20 °C for 5 h. Then, a solution of Boc ₂ O (12.35 g, 56.59 mmol, 13 mL) in THF (200 mL) was added at 0 °C, and the mixture was stirred at 20 °C for 16 h. The target mass peak (24%) was identified by LCMS. The reaction mixture was diluted with H ₂ O (120 mL) and extracted with EtOAc (300 mL × 2). The mixed organic layer was washed with brine (300 mL × 2), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (Biotage; 120 g SepaFlash® silica flash column, eluent of 30–40% EtOAc: petroleum ether gradient, 150 mL/min). The eluate was concentrated under reduced pressure to give the title compound (1.6 g, 4.77 mmol, 13.13% yield) as a pale yellow solid. MS (M + Na) ⁺ = 358.2

¹ H NMR (400 MHz, DMSO- d ₆ ) δ = 8.11 (br s, 1H), 7.39 - 7.28 (m, 5H), 5.07 (s, 2H), 3.50 - 3.34 (m, 4H), 2.73 - 2.57 (m, 4H), 1.37 (s, 9H)

Step 2. Synthesis of benzyl 4-aminopiperazine-1-carboxylate (4)

To a solution of benzyl 4-((tert-butoxycarbonyl)amino)piperazine-1-carboxylate (1 g, 2.98 mmol) in DCM (10 mL) was added TFA (9.21 g, 80.78 mmol, 6 mL) at 0 °C. The mixture was stirred at 20 °C under CN ₂ for 2 h. The main peak of the desired mass was identified by LCMS. The reaction mixture was concentrated under reduced pressure to obtain the title compound (1 g, crude, TFA) as a pale yellow oil. MS(M+H) ⁺ = 236.2.

Step 3. Synthesis of benzyl 4-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)piperazine-1-carboxylate (6)

A mixture of 3-(4-bromophenyl)piperidine-2,6-dione (800 mg, 2.98 mmol), benzyl 4-aminopiperazine-1-carboxylate (1.0 g, 2.86 mmol, TFA salt), GPhos Pd G6 (274.29 mg, 290.42 μmol,), TEA (1.51 g, 14.92 mmol, 2.08 mL), Cs ₂ CO ₃ (2.92 g, 8.95 mmol) in dioxane (30 mL) was degassed and purified with N ₂ After purging three times, the mixture was stirred at 100 °C under CN ₂ for 16 hours. By LCMS The peak of the target mass was confirmed. The reaction mixture was filtered, the filter cake was washed with THF (100 mL), and the filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (Biotage; 12 g SepaFlash® silica flash column, eluent of 50–70% EtOAc:Petroleum ether gradient, 150 mL/min) to give the title compound (600 mg, 1.42 mmol, 47.60% yield) as a pale yellow solid. MS(M+H) ⁺ = 423.3

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.75 (s, 1H), 7.42 - 7.30 (m, 5H), 6.96 (d, J = 8.6 Hz, 2H), 6.77 (d, J = 8.4 Hz, 2H), 6.54 (s, 1H), 5.10 (s, 2H), 3.70 - 3.63 (m, 1H), 3.57 - 3.39 (m, 4H), 2.70 - 2.60 (m, 4H), 2.48 - 2.42 (m, 1H), 2.15 - 1.98 (m, 2H), 1.35 - 1.18 (m, 1H)

Step 4. Synthesis of 3-(4-(piperazin-1-ylamino)phenyl)piperidine-2,6-dione (7)

A solution of benzyl 4-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)piperazine-1-carboxylate (200 mg, 473.40 μmol) in TFA (6.00 mL) was stirred at 50 °C under CN ₂ for 12 h. The main peak of the desired mass was confirmed by LCMS. The reaction mixture was concentrated under reduced pressure to obtain the title compound (200 mg, crude, TFA salt) as a yellow oil. MS(M+H) ⁺ = 289.2

Step 5. Synthesis of tert-butyl ((1r,4r)-4-((4-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)piperazin-1-yl)methyl)cyclohexyl)carbamate (9)

The title compound (143 mg, 286.20 μmol, 57.58% yield) was obtained as a yellow solid by a similar method to step 3 of Example 50. MS(M+H) ⁺ = 500.3

Step 6. Synthesis of 3-(4-((4-(((1r,4r)-4-aminocyclohexyl)methyl)piperazin-1-yl)amino)phenyl)piperidine-2,6-dione (10)

To a solution of tert-butyl ((1r,4r)-4-((4-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)piperazin-1-yl)methyl)cyclohexyl)carbamate (143 mg, 286.20 μmol) in DCM (4 mL) was added TFA (255.12 μL) at 20 °C, and the resulting mixture was stirred at 20 °C for 3 h. LCMS confirmed complete consumption of the starting material and the peak of the target mass (80%). The reaction mixture was concentrated under reduced pressure to obtain the title compound (147 mg, crude, TFA salt) as a yellow solid of black oil. MS(M+H) ⁺ = 400.3

Step 7. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-((4-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)piperazin-1-yl)methyl)cyclohexyl)-3-methoxybenzamide (Compound 52)

The title compound (66.8 mg, 73.29 μmol, 37.69% yield, 87% purity) was obtained as a white solid by a similar method to step 5 of Example 50. MS(M+H) ⁺ = 793.6

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.76 (br s, 1H), 8.41 (d, J = 8.9 Hz, 1H), 8.05 (br d, J = 7.8 Hz, 1H), 7.89 (s, 1H), 7.62 (s, 1H), 7.52 - 7.45 (m, 2H), 6.94 (d, J = 8.3 Hz, 2H), 6.74 (d, J = 8.3 Hz, 2H), 6.36 (s, 1H), 4.48 - 4.37 (m, 1H), 4.32 (q, J = 6.7 Hz, 1H), 3.94 (s, 3H), 3.74 (br d, J = 8.5 Hz, 1H), 3.66 (dd, J = 5.0, 10.5 Hz, 1H), 3.23 (s, 3H), 2.80 - 2.56 (m, 5H), 2.46 (br d, J = 4.8 Hz, 1H), 2.43 (br d, J = 4.3 Hz, 1H), 2.16 - 2.06 (m, 3H), 2.05 - 1.96 (m, 2H), 1.94 - 1.74 (m, 9H), 1.71 - 1.51 (m, 3H), 1.44 - 1.44 (m, 1H), 1.39 - 1.30 (m, 2H), 1.23 (d, J = 6.6 Hz, 3H), 1.18 - 1.09 (m, 1H), 1.01 - 0.89 (m, 2H), 0.87 - 0.72 (m, 1H)

Example 53. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-((4-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)cyclohexyl)amino)cyclohexyl)-3-methoxybenzamide (Compound 53)

Step 1. Synthesis of tert-butyl (4-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)cyclohexyl)carbamate (3)

To a solution of 3-(4-aminophenyl)piperidine-2,6-dione (200 mg, 979.31 μmol) in DCE (10 mL) and DMF (2 mL) were added tert-butyl (4-oxocyclohexyl)carbamate (280.00 mg, 1.31 mmol, 280.00 μL) and TEA (363.50 mg, 3.59 mmol, 500 μL). The mixture was stirred at 20 °C for 1 h. Then, NaBH(OAc) ₃ (700 mg, 3.30 mmol) was added to the mixture at 0 °C, and the mixture was stirred at 20 °C for 15 h. The target mass peak (77%) was confirmed by LCMS. To the reaction mixture were added H ₂ O (15 mL) and DCM (20 mL), and then NaHCO ₃ (sat. aq, 20 mL) was added to adjust the pH to 9. The mixture was extracted with DCM (30 mL × 2), and the combined organic layer was washed with brine (30 mL × 2), dried over Na ₂ SO ₄ , filtered, and the filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (10 g SepaFlash® silica flash column, Eluent of 30–40% EtOAc:Petroleum ether gradient, 100 mL/min) to give the title compound (350 mg, 871.74 μmol, 89.01% yield) as a yellow solid. MS (M+ H) ⁺ = 402.3

Step 2. Synthesis of 3-(4-((4-aminocyclohexyl)amino)phenyl)piperidine-2,6-dione (4)

The title compound (150 mg, 443.99 μmol, 50.93% yield, HCl) was obtained as a white solid by a similar method to step 2 of Example 50. MS(M+H) ⁺ = 302.2

Step 3. Synthesis of (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxy-N-(4-oxocyclohexyl)benzamide (5)

To a solution of (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoic acid (300 mg, 729.12 μmol) in DMF (8 mL) were added HATU (350 mg, 920.50 μmol), DIPEA (445.20 mg, 3.44 mmol, 600 μL), and 4-aminocyclohexan-1-one (140 mg, 935.72 μmol, HCl) at 20 °C. The mixture was stirred at 20 °C under CN ₂ for 16 h. The major peak of the desired mass was identified by LCMS. The reaction mixture was diluted with H ₂ O (15 mL), and the mixture was extracted with EtOAc (40 mL × 2). The mixed organic layer was washed with NaHCO ₃ (aq, 40 mL × 2), then with brine (40 mL × 2), dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure to obtain the title compound (300 mg, crude) as an off-white solid. MS (M+H) ⁺ = 507.3

Step 4. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-((4-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)cyclohexyl)amino)cyclohexyl)-3-methoxybenzamide (Compound 53)

To a solution of 3-(4-((4-aminocyclohexyl)amino)phenyl)piperidine-2,6-dione (40 mg, 118.40 μmol, HCl) in DCM (4 mL) and DMF (1 mL) were added (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxy-N-(4-oxocyclohexyl)benzamide (70 mg, 138.18 μmol) and TEA (109.05 mg, 1.08 mmol, 150 μL). The mixture was stirred at 20 °C for 1 h. After that, NaBH(OAc) ₃ (140 mg, 660.56 μmol) was added to the mixture at 0 °C, and the mixture was stirred at 20 °C for 15 h. The peak of the target mass (66%) was confirmed by LCMS. The reaction mixture was added to H ₂ O (10 mL), diluted with DCM (20 mL), and then NaHCO ₃ (sat. aq, 15 mL) was added to adjust the pH to 9. The mixture was extracted with DCM (20 mL × 2), and the mixed organic layer was washed with brine (30 mL × 2), dried over Na ₂ SO ₄ , filtered, and the filtrate was concentrated under reduced pressure. The residue was purified by prep-HPLC (column: Phenomenex Luna C18 150 x 25 mm x10 μm; mobile phase: [H ₂ O (0.1% TFA) -ACN]; gradient: 0% - 30% B over 15.0 min, column Temp: 30 °C). The eluate was lyophilized, and the product was diluted with DCM (10 mL), and then NaHCO ₃ (1 M, 10 mL) was added to adjust the pH to 7~8. The mixture was extracted with DCM (15 mL × 2), concentrated under reduced pressure to remove DCM, and the residue was lyophilized to obtain the title compound (36.0 mg, 44.09 μmol, 37.24% yield, 97% purity) as a white solid. MS (M+H) ⁺ = 792.5

^1H NMR (400 MHz, DMSO _- d6 ) δ = 10.74 (s, 1H), 8.42 (d, J = 8.9 Hz, 1H), 8.07 - 7.96 (m, 1H), 7.90 (s, 1H), 7.63 (s, 1H), 7.54 - 7.44 (m, 2H), 6.88 (d, J = 8.2 Hz, 2H), 6.55 (d, J = 8.3 Hz, 2H), 5.39 - 5.26 (m, 1H), 4.48 - 4.39 (m, 1H), 4.36 - 4.29 (m, 1H), 3.95 (d, J = 1.8 Hz, 3H), 3.87 - 3.73 (m, 1H), 3.66 - 3.58 (m, 1H), 3.24 (s, 3H), 2.86 - 2.72 (m, 1H), 2.70 - 2.53 (m, 2H), 2.49 - 2.37 (m, 2H), 2.12 - 1.89 (m, 5H), 1.88 - 1.73 (m, 6H), 1.68 - 1.48 (m, 13H), 1.42 - 1.32 (m, 1H), 1.23 (d, J = 6.7 Hz, 3H), 1.21 - 1.02 (m, 2H)

Example 54. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-((4-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)cyclohexyl)(methyl)amino)cyclohexyl)-3-methoxybenzamide (Compound 54)

Step 1. Synthesis of tert-butyl (4-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)cyclohexyl)(methyl)carbamate (3)

The title compound (200 mg, 481.32 μmol, 32.77% yield) was obtained as a yellow solid by a similar method to step 1 of Example 50. MS(M+ H) ⁺ = 416.3

Step 2. Synthesis of 3-(4-((4-(methylamino)cyclohexyl)amino)phenyl)piperidine-2,6-dione (4)

The title compound (160 mg, crude, HCl) was obtained as a yellow solid by a similar method to step 2 of Example 50. MS(M+H) ⁺ = 316.2

Step 3. Synthesis of (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxy-N-(4-oxocyclohexyl)benzamide (5)

The title compound (500 mg, crude) was obtained as a grayish-white solid by a similar method to step 3 of Example 50. MS(M+H) ⁺ = 507.3

Step 4. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-((4-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)cyclohexyl)(methyl)amino)cyclohexyl)-3-methoxybenzamide (Compound 54)

To a solution of 3-(4-((4-(methylamino)cyclohexyl)amino)phenyl)piperidine-2,6-dione (60 mg, 170.52 μmol, HCl) in DCM (4 mL) and DMF (1.5 mL) were added (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxy-N-(4-oxocyclohexyl)benzamide (90 mg, 177.66 μmol) and TEA (145.40 mg, 1.44 mmol, 200 μL). The mixture was stirred at 20 °C for 1 h. Then, NaBH(OAc) ₃ (197.51 mg, 931.93 μmol) was added to the mixture at 0 °C. The mixture was stirred at 20 °C for 47 h. The target mass peak (47%) was identified by LCMS. After adding H ₂ O (15 mL) to the reaction mixture, the pH was adjusted to 9 by adding NaHCO ₃ (sat. aq, 30 mL), the mixture was extracted with DCM (25 mL × 2), and the combined organic layer was washed with brine (30 mL × 2), dried over Na ₂ SO ₄ , filtered, and the filtrate was concentrated under reduced pressure. The residue was purified by prep-HPLC (column: Phenomenex Luna C18 150 x 25 mm x 10 um; mobile phase: [H ₂ O (0.1% TFA) -ACN]; gradient: 0% - 30% B over 15.0 min; column Temp: 30 °C). The eluate was diluted with DCM (10 mL), and then NaHCO ₃ (1 M, 15 mL) was added to adjust the pH to 7–8. The mixture was extracted with DCM (15 mL × 2), concentrated under reduced pressure, and lyophilized to obtain the title compound (11.3 mg, 12.90 μmol, 7.56% yield, 92% purity) as a white solid. MS (M+H) ⁺ = 806.6

¹ H NMR (400 MHz, DMSO- d ₆ ) δ = 10.80 - 10.64 (m, 1H), 8.42 (d, J = 8.9 Hz, 1H), 8.05 - 7.96 (m, 1H), 7.90 (s, 1H), 7.65 - 7.59 (m, 1H), 7.51 - 7.45 (m, 2H), 6.92 - 6.84 (m, 2H), 6.62 - 6.53 (m, 2H), 5.49 - 5.40 (m, 1H), 4.47 - 4.39 (m, 1H), 4.36 - 4.28 (m, 1H), 3.94 (d, J = 1.8 Hz, 3H), 3.91 - 3.68 (m, 1H), 3.65 - 3.58 (m, 1H), 3.51 - 3.39 (m, 1H), 3.24 (s, 3H), 2.65 - 2.55 (m, 2H), 2.47 - 2.41 (m, 1H), 2.19 (s, 3H), 2.04 - 1.88 (m, 5H), 1.82 - 1.67 (m, 10H), 1.64 - 1.39 (m, 10H), 1.36 - 1.19 (m, 5H)

Example 55. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-((4-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)cyclohexyl)methyl)piperidin-1-yl)-3-methoxybenzamide (Compound 55)

Step 1. Synthesis of 4-((1,4-dioxaspiro[4.5]decan-8-yl)methyl)pyridine (3)

A solution of 8-methylene-1,4-dioxaspiro[4.5]decane (2 g, 12.97 mmol) in 9-BBN (0.5 M, 33.72 mL) was stirred at 80 °C for 4 h. The mixture was then cooled to 20 °C, and 4-bromopyridine (3.03 g, 15.56 mmol, HCl salt), Pd(dppf)Cl ₂ (949.00 mg, 1.30 mmol), K ₂ CO ₃ (5.38 g, 38.91 mmol), DMF (50 mL), and H ₂ O (10 mL) were slowly added at 20 °C, and the resulting mixture was stirred at 80 °C for 12 h. The target mass peak (52%) was confirmed by LCMS. The reaction mixture was diluted with H ₂ O (150 mL) and extracted with EtOAc (80 mL x 3). The organic layer was washed with brine (80 mL x 3), dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (100 g SepaFlash® silica flash column, Eluent of 12–60% EtOAc/Petroleum ether gradient @ 200 mL/min) to give the title compound (2.8 g, 12.00 mmol, 92.53% yield) as a red oil. MS(M+H) ⁺ = 234.3

Step 2. Synthesis of 4-((1,4-dioxaspiro[4.5]decan-8-yl)methyl)piperidine (4)

To a solution of PtO ₂ (1 g, 4.40 mmol) in EtOH (30 mL) were added 4-((1,4-dioxaspiro[4.5]decan-8-yl)methyl)pyridine (2.8 g, 12.00 mmol) and AcOH (1.44 g, 24.00 mmol, 1.37 mL) under N ₂ . The suspension was degassed and purified three times with H ₂ . The mixture was stirred at 20–60 °C under CH ₂ ( 45 Psi) for 12 h. LCMS confirmed complete consumption of the starting material and the main peak of the desired mass. The reaction mixture was filtered, the filter cake was washed with MeOH (500 mL), and the filtrate was concentrated under reduced pressure to give the title compound (3.6 g, crude, HOAC salt) as a yellow oil. MS(M+H) ⁺ = 240.1

Step 3. Synthesis of 4-((1,4-dioxaspiro[4.5]decan-8-yl)methyl)-1-nitrosopiperidine (5)

To a solution of 4-((1,4-dioxaspiro[4.5]decan-8-yl)methyl)piperidine (1.1 g, 3.67 mmol, HOAC salt) in _H2O (12 mL) was added _NaNO2 (760.46 mg, 11.02 mmol) at 20 °C. AcOH (882.51 mg, 14.70 mmol, 841.29 μL) was then added at 20 °C, and the resulting mixture was stirred at 20 °C for 12 h. LCMS confirmed complete consumption of the starting material and the peak of the target mass (85%). After adjusting the pH to ₁₀ with _{Na2CO3 ,} the mixture was extracted with EtOAc (30 mL x 3). The organic layer was dried _{over Na2SO4} , filtered, and concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (20 g SepaFlash® silica flash column, eluent of 5–25% EtOAc/Petroleum ether gradient @ 200 mL/min) to give the title compound (1.1 g, crude) as a yellow solid. MS(M+H) ⁺ = 269.1

Step 4. Synthesis of benzyl (4-((1,4-dioxaspiro[4.5]decan-8-yl)methyl)piperidin-1-yl)carbamate (7)

To a solution of 4-((1,4-dioxaspiro[4.5]decan-8-yl)methyl)-1-nitrosopiperidine (1.1 g, 4.10 mmol) in THF (12 mL) and H ₂ O (4 mL) was added NH ₄ Cl (1.75 g, 32.79 mmol) at 0 °C. Zn (1.34 g, 20.50 mmol) was then added at 0 °C, and the resulting mixture was stirred at 20 °C for 2 h. Complete consumption of the starting material was confirmed by LCMS. The reaction mixture was filtered, and the filter cake was washed with the mixed solution (150 mL, THF:H ₂ O=2:1). NaOH (983.71 mg, 24.59 mmol) was added to the filtrate at 0 °C. After that, CbzCl (1.05 g, 6.15 mmol, 877.76 μL) was added dropwise at 0 °C, and the resulting mixture was stirred at 20 °C for 12 h. LCMS confirmed complete consumption of the starting material and the peak of the target mass (16%). The reaction mixture was diluted with H ₂ O (60 mL) and extracted with EtOAc (30 mL x 3). The organic layer was dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (20 g SepaFlash® silica flash column, Eluent of 5–25% EtOAc/Petroleum ether gradient @ 200 mL/min) to give the title compound (949 mg, 2.44 mmol, 59.59% yield) as a yellow oil. MS(M+H) ⁺ = 389.1

Step 5. Synthesis of benzyl (4-((4-oxocyclohexyl)methyl)piperidin-1-yl)carbamate (8)

To a solution of benzyl (4-((1,4-dioxaspiro[4.5]decan-8-yl)methyl)piperidin-1-yl)carbamate (949 mg, 2.44 mmol) in dioxane (2 mL) and H ₂ O (2 mL) was added HCOOH (12 mL) at 20 °C, and the resulting mixture was stirred at 20 °C for 12 h. LCMS confirmed complete consumption of the starting material and the peak of the target mass (47%). The reaction mixture was diluted with H ₂ O (20 mL), and the pH was adjusted to 10 with saturated Na ₂ CO ₃ . The mixture was extracted with EtOAc (20 mL x 3). The organic layer was dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (10 g SepaFlash® silica flash column, eluent of 10–33% EtOAc/Petroleum ether gradient @ 200 mL/min) to give the title compound (456 mg, 1.32 mmol, 54.20% yield) as a white solid. MS(M+H) ⁺ = 345.0

Step 6. Synthesis of benzyl (4-((4-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)cyclohexyl)methyl)piperidin-1-yl)carbamate (10)

To a solution of benzyl (4-((4-oxocyclohexyl)methyl)piperidin-1-yl)carbamate (226 mg, 656.12 μmol) and 3-(4-aminophenyl)piperidine-2,6-dione (201.00 mg, 984.19 μmol) in DCM (8 mL) and DMF (2 mL) was added TEA (199.18 mg, 1.97 mmol, 273.97 μL) at 20 °C, and the mixture was stirred for 12 h. Then, NaBH(OAc) ₃ (417.18 mg, 1.97 mmol) was added at 20 °C, and the resulting mixture was stirred at 20 °C for 2 h. LCMS confirmed the remaining benzyl (4-((4-oxocyclohexyl)methyl)piperidin-1-yl)carbamate and the peak of the target mass (15%). The reaction mixture was diluted with H ₂ O (20 mL) and extracted with DCM (20 mL x 3). The organic layer was washed with saturated NaHCO ₃ (20 mL x 3), dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure. The residue was purified by prep-HPLC (column: Phenomenex Luna C18 150*25 mm*10um; mobile phase: [H ₂ O (0.1% TFA) - ACN]; gradient: 3% - 33% B over 15.0 min), and the eluate was lyophilized to obtain the title compound (91 mg, 170.84 μmol, 26.04% yield) as a white solid. MS(M+H) ⁺ =533.4

Step 7. Synthesis of 3-(4-((4-((1-aminopiperidin-4-yl)methyl)cyclohexyl)amino)phenyl)piperidine-2,6-dione (11)

A mixture of benzyl (4-((4-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)cyclohexyl)methyl)piperidin-1-yl)carbamate (91 mg, 170.84 μmol) in TFA (4 mL) was stirred at 40 °C for 12 h. LCMS confirmed complete consumption of the starting material and the peak of the target mass (70%). The reaction mixture was concentrated under reduced pressure to obtain the title compound (88 mg, crude, TFA salt) as a yellow oil. MS(M+H) ⁺ = 399.3

Step 8. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-((4-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)cyclohexyl)methyl)piperidin-1-yl)-3-methoxybenzamide (Compound 55)

The title compound (20.3 mg, 23.33 μmol, 23.99% yield, 91% purity) was obtained as a white solid by a similar method to step 3 of Example 51. MS(M+H) ⁺ = 792.4

^1H NMR (400 MHz, DMSO _- d6 ) δ = 10.71 (s, 1H), 9.23 (s, 1H), 8.41 (d, J = 8.9 Hz, 1H), 7.89 (s, 1H), 7.62 (s, 1H), 7.45 - 7.37 (m, 2H), 6.88 (d, J = 8.2 Hz, 2H), 6.55 (br d, J = 8.2 Hz, 2H), 5.38 - 5.31 (m, 1H), 4.47 - 4.37 (m, 1H), 4.32 (q, J = 7.0 Hz, 1H), 3.93 (s, 3H), 3.66 - 3.58 (m, 1H), 3.47 - 3.40 (m, 1H), 3.23 (s, 3H), 2.99 (br d, J = 11.0 Hz, 2H), 2.76 (br t, J = 11.1 Hz, 2H), 2.65 - 2.55 (m, 1H), 2.47 - 2.41 (m, 1H), 2.14 - 1.98 (m, 3H), 1.96 - 1.89 (m, 1H), 1.85 - 1.75 (m, 4H), 1.68 (br d, J = 13.0 Hz, 2H), 1.64 - 1.55 (m, 5H), 1.53 - 1.42 (m, 4H), 1.38 - 1.30 (m, 3H), 1.23 (br d, J = 6.7 Hz, 3H), 1.18 (br d, J = 7.2 Hz, 2H), 0.88 - 0.80 (m, 1H), 0.79 - 0.71 (m, 1H)

Example 56. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(1-((4-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)cyclohexyl)methyl)piperidin-4-yl)-3-methoxybenzamide (Compound 56)

Step 1. Synthesis of 3-(4-((4-(hydroxymethyl)cyclohexyl)amino)phenyl)piperidine-2,6-dione (3)

The title compound (360 mg, 1.14 mmol, 46.47% yield) was obtained as a pale yellow solid by a similar method to step 1 of Example 53. MS(M+ H) ⁺ = 317.2

Step 2. Synthesis of 4-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)cyclohexane-1-carbaldehyde (4)

To a solution of 3-(4-((4-(hydroxymethyl)cyclohexyl)amino)phenyl)piperidine-2,6-dione (200 mg, 632.12 μmol) in DMSO (3 mL) and DCM (6 mL) were added TEA (255.86 mg, 2.53 mmol, 351.93 μL) and SO ₃ . Py (213.33 mg, 1.34 mmol). The mixture was stirred at 20 °C for 2 h. The peak of the target mass was identified by LCMS. To the reaction mixture, H ₂ O (10 mL) and DCM (15 mL) were added, and then NaHCO ₃ (sat. aq, 10 mL) was added to adjust the pH to 9. After the mixture was extracted with DCM (15 mL × 2), the mixed organic layer was washed with brine (15 mL × 2), dried over Na ₂ SO ₄ , filtered, and the filtrate was concentrated under reduced pressure to obtain the title compound (198 mg, crude) as a yellow oil. MS (M + H ₂ O + H) ⁺ = 333.1

Step 3. Synthesis of tert-butyl (1-((4-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)cyclohexyl)methyl)piperidin-4-yl)carbamate (5)

To a solution of 4-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)cyclohexane-1-carbaldehyde (198 mg, 629.82 μmol) in DCM (10 mL) and DMF (2 mL) were added tert-butyl piperidin-4-ylcarbamate (260 mg, 1.30 mmol) and HOAc (37.82 mg, 629.82 μmol, 36.05 μL). The mixture was stirred at 25 °C for 1 h. Then, NaBH(OAc) ₃ (577.50 mg, 2.72 mmol) was added to the mixture at 25 °C, and the mixture was stirred at 25 °C for 15 h. By LCMS The target mass peak (31%) was confirmed. After adding H ₂ O (10 mL) to the reaction mixture at 0 °C, NaHCO ₃ (sat. aq, 15 mL) was added at 0 °C to adjust the pH to 9. The combined aqueous layers were extracted with DCM (20 mL × 3), and the mixed organic layers were washed with brine (30 mL × 2), dried over Na ₂ SO ₄ , filtered, and the filtrate was concentrated under reduced pressure. The residue was purified by prep-HPLC (column: Phenomenex Luna C18 150 x 25 mm x 10 μm; mobile phase: [H ₂ O (0.1% TFA) -ACN]; gradient: 0% - 25% B over 15.0 min; column Temp: 30 °C) and the eluate was lyophilized to obtain the title compound (200 mg, 401.08 μmol, 63.68% yield) as a pale yellow solid. MS (M+H) ⁺ = 499.4

Step 4. Synthesis of 3-(4-((4-((4-aminopiperidin-1-yl)methyl)cyclohexyl)amino)phenyl)piperidine-2,6-dione (6)

To a solution of tert-butyl (1-((4-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)cyclohexyl)methyl)piperidin-4-yl)carbamate (200 mg, 401.08 μmol) in dioxane (3 mL) was added HCl/dioxane (2 M, 20 mL) at 20 °C, and the mixture was stirred at 20 °C for 2 h. The main peak of the desired mass was identified by LCMS. The reaction mixture was concentrated under reduced pressure to obtain the title compound (160 mg, crude, HCl) as a white solid. MS(M+H) ⁺ = 399.3

Step 5. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(1-((4-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)cyclohexyl)methyl)piperidin-4-yl)-3-methoxybenzamide (Compound 56)

The title compound (26.9 mg, 33.63 μmol, 19.76% yield, 99% purity) was obtained as a white solid by a similar method to step 8 of Example 55. MS(M+H) ⁺ = 792.6

¹ H NMR (400 MHz, DMSO- d ₆ ) δ = 10.75 (s, 1H), 8.46 - 8.39 (m, 1H), 8.10 - 8.02 (m, 1H), 7.90 (s, 1H), 7.63 (s, 1H), 7.52 - 7.45 (m, 2H), 6.89 (d, J = 8.4 Hz, 2H), 6.60 - 6.49 (m, 2H), 5.40 - 5.30 (m, 1H), 4.48 - 4.37 (m, 1H), 4.36 - 4.27 (m, 1H), 3.94 (s, 3H), 3.83 - 3.71 (m, 1H), 3.66 - 3.58 (m, 1H), 3.48 - 3.40 (m, 1H), 3.24 (s, 3H), 2.93 - 2.79 (m, 2H), 2.68 - 2.58 (m, 1H), 2.43 - 2.37(m, 1H), 2.22 - 2.12 (m, 2H), 2.10 - 1.89 (m, 6H), 1.84 - 1.71 (m, 6H), 1.67 - 1.46 (m, 11H), 1.43 - 1.32 (m, 2H), 1.23 (d, J = 6.6 Hz, 3H)

Example 57. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-((4-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)cyclohexyl)methyl)piperazin-1-yl)-3-methoxybenzamide (Compound 57)

Step 1. Synthesis of tert-butyl 4-(((benzyloxy)carbonyl)amino)piperazine-1-carboxylate (2)

To a solution of tert-butyl piperazine-1-carboxylate (5 g, 26.85 mmol) in H ₂ O (60 mL) was added NaOH (6.44 g, 161.07 mmol) at 20 °C. Aminohydrogen sulfate (4.55 g, 40.27 mmol) was added at 20 °C, and the resulting mixture was stirred at 20 °C for 12 h. THF (120 mL) and CbzCl (6.87 g, 40.27 mmol, 5.75 mL) were added at 20 °C, and the resulting mixture was stirred at 20 °C for 4 h. LCMS confirmed complete consumption of the starting material and the peak of the target mass (13%). The reaction mixture was diluted with H ₂ O (300 mL) and extracted with EtOAc (200 mL x 3). The organic layer was dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (80 g SepaFlash® silica flash column, eluent of 12–40% EtOAc/petroleum ether gradient @ 100 mL/min). The product was triturated with MTBE (15 mL) at 20 °C for 0.5 h and filtered. The filter cake was dried under reduced pressure to obtain the title compound (1 g, 2.98 mmol, 11.11% yield) as a white solid. MS (M-56+H) ⁺ = 280.2

Step 2. Synthesis of benzyl piperazin-1-ylcarbamate (3)

The title compound (3.1 g, crude, TFA salt) as a yellow oil was obtained by a similar method to step 2 of Example 52. MS(M+H) ⁺ = 236.1

Step 3. Synthesis of benzyl (4-((1,4-dioxaspiro[4.5]decan-8-yl)methyl)piperazin-1-yl)carbamate (5)

To a solution of 1,4-dioxaspiro[4.5]decane-8-carbaldehyde (0.4 g, 2.35 mmol) and benzyl piperazin-1-ylcarbamate (1.23 g, 3.53 mmol, TFA salt) in DCM (14 mL) were added TEA (2.85 g, 28.20 mmol, 3.93 mL) and MgSO ₄ (424.31 mg, 3.53 mmol) at 20 °C. After stirring for 1 h, NaBH(OAc) ₃ (1.49 g, 7.05 mmol) was added at 20 °C, and the resulting mixture was stirred at 20 °C for 12 h. LCMS confirmed complete consumption of the starting material and the peak of the target mass (50%). The reaction mixture was diluted with H ₂ O (20 mL) and extracted with DCM (20 mL x 3). The organic layer was washed with saturated NaHCO ₃ (20 mL x 3), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure to obtain the title compound (840 mg, 2.16 mmol, 91.77% yield) as an orange solid. MS(M+H) ⁺ = 390.1

Step 4. Synthesis of benzyl (4-((4-oxocyclohexyl)methyl)piperazin-1-yl)carbamate (6)

The title compound (740 mg, 2.14 mmol, 99.33% yield) was obtained as a yellow solid by a similar method to step 6 of Example 55. MS(M+H) ⁺ = 346.1

Step 5. Synthesis of benzyl (4-((4-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)cyclohexyl)methyl)piperazin-1-yl)carbamate (8)

The title compound (62 mg, 116.18 μmol, 7.43% yield) was obtained as a white solid by a similar method to step 7 of Example 55. MS(M+H) ⁺ = 534.4

Step 6. Synthesis of 3-(4-((4-((4-aminopiperazin-1-yl)methyl)cyclohexyl)amino)phenyl)piperidine-2,6-dione (9)

The title compound (60 mg, crude, TFA salt) was obtained as a yellow oil by a similar method to step 8 of Example 55. MS(M+H) ⁺ = 400.3

Step 7. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-((4-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)cyclohexyl)methyl)piperazin-1-yl)-3-methoxybenzamide (Compound 57)

The title compound (3.2 mg, 3.39 μmol, 2.90% yield, 84% purity) was obtained as a white solid by a similar method to step 9 of Example 55. MS(M+H) ⁺ = 793.4

^1H NMR (400 MHz, DMSO _- d6 ) δ = 10.72 (s, 1H), 9.26 (s, 1H), 8.42 (d, J = 8.9 Hz, 1H), 7.90 (s, 1H), 7.63 (s, 1H), 7.44 - 7.38 (m, 2H), 6.87 (d, J = 8.5 Hz, 2H), 6.53 - 6.47 (m, 2H), 5.32 (br d, J = 7.9 Hz, 1H), 4.47 - 4.37 (m, 1H), 4.36 - 4.28 (m, 1H), 3.93 (s, 3H), 3.65 - 3.57 (m, 1H), 3.23 (s, 3H), 3.13 - 3.05 (m, 1H), 2.92 (br s, 4H), 2.65 - 2.54 (m, 2H), 2.44 (br dd, J = 4.8, 12.3 Hz, 4H), 2.13 (br d, J = 5.6 Hz, 2H), 2.03 - 1.96 (m, 4H), 1.94 - 1.89 (m, 1H), 1.85 - 1.71 (m, 7H), 1.65 - 1.60 (m, 2H), 1.51 - 1.44 (m, 1H), 1.23 (d, J = 6.8 Hz, 3H), 1.15 - 1.05 (m, 2H), 1.04 - 0.92 (m, 2H)

Example 58. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-((4-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)cyclohexyl)amino)piperidin-1-yl)-3-methoxybenzamide (Compound 58)

To a solution of (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxy-N-(4-oxopiperidin-1-yl)benzamide (50 mg, 98.51 μmol) in DMAC (3 mL) was added 3-(4-((4-aminocyclohexyl)amino)phenyl)piperidine-2,6-dione (30 mg, 99.54 μmol) and TEA (72.70 mg, 718.46 μmol, 100 μL). The mixture was stirred at 20 °C for 1 h. Then, NaBH ₃ CN (50 mg, 795.65 μmol) was added at 0 °C, and the mixture was stirred at 20 °C for 15 h. The peak of the target mass was identified by LCMS. The reaction mixture was diluted with H ₂ O (10 mL) and DCM (25 mL), and then adjusted to pH = 9 by adding NaHCO ₃ (sat. aq, 20 mL). The mixture was extracted with DCM (25 mL × 2), and the combined organic layer was washed with brine (20 mL × 2), dried over anhydrous Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by prep-HPLC (column: Phenomenex Luna C18 150 x 25 mm x 10 μm; mobile phase: [H ₂ O (0.1% TFA) - ACN]; gradient: 0% - 28% B over 15.0 min, column Temp: 30 °C), and the eluate was lyophilized. The product was diluted with DCM (10 mL), and then adjusted to pH = 7~8 by adding NaHCO ₃ (1 M, 10 mL). The mixture was extracted with DCM (15 mL × 2). The combined organic layer was concentrated under reduced pressure and lyophilized, and the product was repurified by prep-HPLC (column: Waters xbridge 150 x 25 mm x10 μm; mobile phase: [H ₂ O (10 mM NH ₄ HCO ₃ ) - ACN]; gradient: 30% - 60% B over 15.0 min, column Temp: 30 °C). The eluate was lyophilized to obtain the title compound as a white solid (11.9 mg, 14.86 μmol, 15.08% yield, 99% purity). MS (M + H) ⁺ = 793.6

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.74 (s, 1H), 9.24 (s, 1H), 8.45 - 8.38 (m, 1H), 7.90 (s, 1H), 7.63 (s, 1H), 7.46 - 7.37 (m, 2H), 6.88 (d, J = 8.4 Hz, 2H), 6.55 (d, J = 8.6 Hz, 2H), 5.40 - 5.30 (m, 1H), 4.49 - 4.38 (m, 1H), 4.36 - 4.28 (m, 1H), 3.94 (s, 3H), 3.66 -3.58 (m, 1H), 3.33 - 3.30 (m, 2H), 3.24 (s, 3H), 3.05 - 2.95 (m, 2H), 2.84 - 2.70 (m, 3H), 2.66 - 2.52 (m, 2H), 2.48 - 2.42 (m, 1H), 2.11 - 1.89 (m, 4H), 1.86 - 1.70 (m, 6H), 1.70 - 1.46 (m, 10H), 1.42 - 1.28 (m, 2H), 1.23 (d, J = 6.7 Hz, 3H).

Example 59. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(2-(4-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperazin-1-yl)ethyl)piperidin-1-yl)-3-methoxybenzamide (Compound 59)

Step 1. Synthesis of tert-butyl (4-(2-(4-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperazin-1-yl)ethyl)piperidin-1-yl)carbamate (3)

To a solution of 3-(4-(piperazin-1-yl)phenyl)piperidine-2,6-dione (250 mg, 807.00 μmol, HCl) in DCM (5 mL) were added TEA (244.98 mg, 2.42 mmol, 336.97 μL), 4A MS (300 mg), and tert-butyl (4-(2-oxoethyl)piperidin-1-yl)carbamate (300 mg, 1.24 mmol), and the resulting mixture was stirred at 20 °C for 0.5 h. NaBH(OAc) ₃ (256.55 mg, 1.21 mmol) was added, and the resulting mixture was stirred at 20 °C for 14 h. The target mass peak (62%) was identified by LCMS. The mixture was diluted with water (20 mL) and DCM (20 mL x 3) and extracted. The mixed organic layer was washed with brine (20 mL), dried over Na ₂ SO ₄ , filtered, and the filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (5 g SepaFlash® silica flash column, eluent of 0–100% EtOAc/Petroleum ether gradient @ 50 mL/min) to give the title compound (0.4 g, 800.57 μmol, 99.20% yield) as a yellow solid. MS (M+H) ⁺ = 500.4

Step 2. Synthesis of 3-(4-(4-(2-(1-aminopiperidin-4-yl)ethyl)piperazin-1-yl)phenyl)piperidine-2,6-dione (4)

A mixture of tert-butyl (4-(2-(4-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperazin-1-yl)ethyl)piperidin-1-yl)carbamate (400 mg, 800.57 μmol) in HCl/dioxane (2 M, 10 mL) was stirred at 20 °C for 0.5 h. The peak of the target mass (67%) was confirmed by LCMS. The mixture was concentrated under reduced pressure to obtain the title compound (0.4 g, crude, HCl) as a brown solid. MS(M+H) ⁺ = 400.3

Step 3. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(2-(4-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperazin-1-yl)ethyl)piperidin-1-yl)-3-methoxybenzamide (Compound 59)

To a solution of 3-(4-(4-(2-(1-aminopiperidin-4-yl)ethyl)piperazin-1-yl)phenyl)piperidine-2,6-dione (80 mg, 183.49 μmol, HCl) and (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoic acid (45.82 mg, 111.36 μmol) in DMF (1 mL) were added HATU (69.77 mg, 183.49 μmol) and DIPEA (71.14 mg, 550.47 μmol, 95.88 μL), and the mixture was stirred at 20 °C for 17 h. The peak of the target mass (27%) was identified by LCMS. The mixture was diluted with H ₂ O (20 mL), extracted with EtOAc (10 mL x 3), and the combined organic layers were washed with brine (20 mL), dried over Na ₂ SO ₄ , filtered, and the filtrate was concentrated under reduced pressure. The residue was purified by prep-HPLC (column: Phenomenex Luna C18 150*25 mm*10 um; mobile phase: [H ₂ O (0.1% TFA)-ACN]; gradient: 5%-35% B over 15.0 min), and the eluate was lyophilized. The desired product was purified with H ₂ O (20 mL) and adjusted to pH = 8~9 by adding NaHCO ₃ . The resulting suspension was extracted with EtOAc (10 mL x 3), and the combined organic layers were dried over Na ₂ SO ₄ and filtered. The filtrate was concentrated under reduced pressure, and the residue was lyophilized to obtain the title compound as a white solid (13.8 mg, 15.31 μmol, 8.35% yield, 88% purity). MS(M+H) ⁺ = 793.5

^1H NMR (400 MHz, DMSO- d6 ) δ = 10.85 (s, _1H ), 9.31 (s, 1H), 8.49 (d, J = 8.7 Hz, 1H), 7.97 (s, 1H), 7.70 (s, 1H), 7.52 - 7.43 (m, 2H), 7.12 (d, J = 7.9 Hz, 2H), 6.96 (d, J = 8.2 Hz, 2H), 4.55 - 4.45 (m, 1H), 4.43 - 4.36 (m, 1H), 4.00 (s, 3H), 3.84 - 3.76 (m, 1H), 3.30 (s, 3H), 3.21 - 3.15 (m, 4H), 3.10 - 3.04 (m, 2H), 2.87 - 2.78 (m, 2H), 2.75 - 2.65 (m, 2H), 2.53 - 2.48 (m, 1H), 2.47 - 2.39 (m, 2H), 2.27 - 2.17 (m, 1H), 2.11 - 2.05 (m, 2H), 2.02 - 1.95 (m, 1H), 1.90 - 1.78 (m, 7H), 1.73 - 1.65 (m, 3H), 1.58 - 1.48 (m, 2H), 1.41 - 1.36 (m, 3H), 1.30 (d, J = 6.6 Hz, 4H).

Example 60. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(1-(2-(4-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperazin-1-yl)ethyl)piperidin-4-yl)-3-methoxybenzamide (Compound 60)

Step 1. Synthesis of tert-butyl (1-(2-hydroxyethyl)piperidin-4-yl)carbamate (2)

To a solution of tert-butyl N-(4-piperidyl)carbamate (5 g, 24.97 mmol) and 2-bromoethanol (3.12 g, 24.97 mmol, 1.77 mL) in DMF (50 mL) was added K ₂ CO ₃ (6.90 g, 49.93 mmol) at 20 °C, and the resulting mixture was stirred at 20 °C for 12 h. The reaction mixture was diluted with H ₂ O (200 mL) and extracted with EtOAc (200 mL x 3). The organic layer was washed with brine (200 mL x 3), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure to give the title compound (4.7 g, 19.24 mmol, 77.05% yield) as a yellow oil.

Step 2. Synthesis of tert-butyl (1-(2-chloroethyl)piperidin-4-yl)carbamate (3)

To a solution of tert-butyl (1-(2-hydroxyethyl)piperidin-4-yl)carbamate (0.7 g, 2.86 mmol) in DCM (25 mL) was added Py (453.24 mg, 5.73 mmol, 462.49 μL) under 0 °C CN ₂ . Then, SOCl ₂ (511.27 mg, 4.30 mmol) was added dropwise at 0 °C, and the resulting mixture was stirred at 20 °C for 2 h. TLC (SiO ₂ , DCM:MeOH=10:1) confirmed complete consumption of the starting material and three new spots. The reaction mixture was diluted with H ₂ O (50 mL), and the pH was adjusted to ~8 with saturated NaHCO ₃ . The suspension was extracted with DCM (30 mL x 3), and the organic layer was dried over Na ₂ SO ₄ and filtered. The filtrate was concentrated under reduced pressure to obtain the title compound (754 mg, crude) as a yellow solid.

Step 3. Synthesis of tert-butyl (1-(2-(4-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperazin-1-yl)ethyl)piperidin-4-yl)carbamate (5)

To a solution of 3-(4-(piperazin-1-yl)phenyl)piperidine-2,6-dione (0.35 g, 1.13 mmol, HCl salt) and tert-butyl (1-(2-chloroethyl)piperidin-4-yl)carbamate (742.21 mg, 2.82 mmol) in ACN (10 mL) and DMF (2 mL) were added NaI (169.35 mg, 1.13 mmol) and DIPEA (876.11 mg, 6.78 mmol, 1.18 mL) at 20 °C, and the resulting mixture was stirred at 60 °C for 12 h. LCMS confirmed complete consumption of the starting material and the peak of the target mass (58%). The reaction mixture was diluted with H ₂ O (40 mL) and extracted with EtOAc (30 mL x 3). The organic layer was washed with brine (30 mL x 3), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure, and the residue was purified by flash silica gel chromatography (40 g SepaFlash® silica flash column, eluent of 30–100% EtOAc/Petroleum ether to 10–10% Methanol/DCM gradient @ 200 mL/min) to give the title compound (230 mg, 460.33 μmol, 40.74% yield) as a yellow solid. MS(M+H) ⁺ = 500.3

Step 4. Synthesis of 3-(4-(4-(2-(4-aminopiperidin-1-yl)ethyl)piperazin-1-yl)phenyl)piperidine-2,6-dione (6)

To a solution of tert-butyl (1-(2-(4-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperazin-1-yl)ethyl)piperidin-4-yl)carbamate (230 mg, 460.33 μmol) in DCM (4 mL) was added HCl/dioxane (2 M, 20 mL) at 20 °C, and the resulting mixture was stirred at 20 °C for 0.5 h. LCMS confirmed complete consumption of the starting material and the peak of the target mass (84%). The reaction mixture was concentrated under reduced pressure to obtain the title compound (201 mg, crude, HCl salt) as a yellow solid. MS(M+H) ⁺ = 400.3

Step 5. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(1-(2-(4-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperazin-1-yl)ethyl)piperidin-4-yl)-3-methoxybenzamide (Compound 60)

The title compound (68.7 mg, 84.90 μmol, 27.95% yield, 98% purity) was obtained as a white solid by a similar method to step 3 of Example 59. MS(M+H) ⁺ = 793.6

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.77 (s, 1H), 8.42 (d, J = 8.9 Hz, 1H), 8.07 (br d, J = 7.6 Hz, 1H), 7.90 (s, 1H), 7.63 (s, 1H), 7.53 - 7.43 (m, 2H), 7.04 (d, J = 8.5 Hz, 2H), 6.88 (br d, J = 8.5 Hz, 2H), 4.49 - 4.38 (m, 1H), 4.32 (q, J = 6.5 Hz, 1H), 3.94 (s, 3H), 3.82 - 3.68 (m, 2H), 3.23 (s, 3H), 3.14 - 3.05 (m, 4H), 2.92 (br d, J = 11.3 Hz, 2H), 2.68 - 2.61 (m, 1H), 2.55 (br d, J = 5.1 Hz, 4H), 2.47 - 2.43 (m, 4H), 2.19 - 2.07 (m, 1H), 2.01 (br t, J = 9.9 Hz, 4H), 1.95 - 1.88 (m, 1H), 1.84 - 1.76 (m, 5H), 1.64 - 1.52 (m, 4H), 1.23 (d, J = 6.6 Hz, 3H), 1.19 - 1.14 (m, 1H), 0.88 - 0.76 (m, 1H)

Example 61. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(2-(4-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperazin-1-yl)ethyl)piperidin-1-yl)-3-(2-hydroxyethoxy)benzamide (Compound 61)

To a solution of (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-(2-hydroxyethoxy)benzoic acid (450 mg, 1.02 mmol) and HATU (229.52 mg, 603.64 μmol) in DMF (6 mL) was added DIPEA (742.00 mg, 5.74 mmol, 1 mL), and the mixture was stirred at 15 °C for 15 min. Afterwards, a solution of 3-(4-(4-(2-(1-aminopiperidin-4-yl)ethyl)piperazin-1-yl)phenyl)piperidine-2,6-dione (310 mg, 603.64 μmol, TFA) in DMF (6 mL) was added at 0 °C, and the mixture was stirred at 15 °C for an additional 1 h. The peak of the target mass was identified by LCMS. The mixture was diluted with EtOAc (10 mL) and saturated NaHCO ₃ (10 mL), and extracted with DCM (10 mL x 3). The combined organic layer was washed with saturated NaHCO ₃ (20 mL), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure. The product was purified by prep-HPLC (column: Waters Xbridge C18 150*50 mm* 10 μm; mobile phase: [water (NH ₄ HCO ₃ ) -ACN]; gradient: 23%-53% B over 10 min), and the eluate was lyophilized. The product was diluted with MeOH (6 mL), MeCN (15 mL), and deionized water (90 mL), and the suspension was lyophilized to obtain the title compound (124.91 mg, 142.67 μmol, 23.63% yield, 94% purity) as a white solid. MS(M+H) ⁺ =823.7

^1H NMR (400 MHz, DMSO _- d6 ) δ = 10.77 (s, 1H), 9.20 (s, 1H), 8.43 (d, J = 8.8 Hz, 1H), 8.06 (s, 1H), 7.90 (s, 1H), 7.45 - 7.36 (m, 2H), 7.05 (d, J = 8.6 Hz, 2H), 6.89 (br d, J = 8.4 Hz, 2H), 5.17 (t, J = 5.8 Hz, 1H), 4.48 - 4.38 (m, 1H), 4.33 (q, J = 6.7 Hz, 1H), 4.12 (br t, J = 4.5 Hz, 2H), 3.82 - 3.69 (m, 3H), 3.24 (s, 3H), 3.16 - 3.07 (m, 4H), 3.03 - 2.96 (m, 2H), 2.81 - 2.71 (m, 2H), 2.65 - 2.58 (m, 1H), 2.48 - 2.42 (m, 3H), 2.39 - 2.31 (m, 2H), 2.19 - 2.08 (m, 1H), 2.07 - 1.88 (m, 4H), 1.85 - 1.55 (m, 9H), 1.49 - 1.40 (m, 2H), 1.36 - 1.19 (m, 6H).

Example 62. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(2-(4-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperazin-1-yl)ethyl)piperidin-1-yl)-3-(2-hydroxyethoxy)benzamide (Compound 62)

Step 1. Synthesis of (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-(2-hydroxyethoxy)benzoic acid (2)

The title compound (2.8 g, crude) was obtained as a yellow solid by a similar method to step 3 of Example 13. MS(M+H) ⁺ = 456.2.

Step 2. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(2-(4-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperazin-1-yl)ethyl)piperidin-1-yl)-3-(2-hydroxyethoxy)benzamide (Compound 62)

The title compound (325.35 mg, 365.38 μmol, 52.12% yield, 94% purity) was obtained as a white solid by a similar method to step 4 of Example 13. MS(M+H) ⁺ =837.5.

SFC Method details: "Column: Chiralpak AS-3 50Х4.6mm ID, 3um Mobile phase: Phase A for CO ₂ , and Phase B for EtOH+ACN (0.05% DEA) ; Gradient elution: 40% EtOH+ACN (0.05% DEA) in CO ₂ Flow rate: 3mL/min;Detector: PDA Column Temp: 35C;Back Pressure: 100Bar"

^1H NMR (400 MHz, DMSO _- d6 ) δ = 10.77 (s, 1H), 9.20 (s, 1H), 8.42 (d, J = 8.9 Hz, 1H), 8.01 (s, 1H), 7.84 (s, 1H), 7.43 - 7.36 (m, 2H), 7.05 (d, J = 8.6 Hz, 2H), 6.88 (br d, J = 8.7 Hz, 2H), 5.15 (t, J = 5.8 Hz, 1H), 4.41 - 4.30 (m, 1H), 4.24 (dd, J = 3.6, 7.5 Hz, 1H), 4.11 (br t, J = 4.5 Hz, 2H), 3.83 - 3.69 (m, 3H), 3.25 (s, 3H), 3.14 - 3.07 (m, 4H), 3.03 - 2.94 (m, 2H), 2.80 - 2.70 (m, 2H), 2.68 - 2.56 (m, 1H), 2.47 - 2.41 (m, 3H), 2.35 (br t, J = 7.5 Hz, 2H), 2.18 - 2.07 (m, 1H), 2.06 - 1.53 (m, 15H), 1.49 - 1.38 (m, 2H), 1.36 - 1.22 (m, 3H), 0.76 (t, J = 7.5 Hz, 3H).

Example 63. Synthesis of N-(4-(2-(4-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperazin-1-yl)ethyl)piperidin-1-yl)-4-(((R)-8-ethyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzamide (Compound 63)

The title compound (15.7 mg, 20.44 μmol, 17.49% yield, 98% purity) was obtained as a white solid by a similar method to step 3 of Example 59. MS(M+H) ⁺ = 753.4

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.87 - 10.68 (m, 1H), 9.20 (s, 1H), 8.46 (d, J = 8.4 Hz, 1H), 7.84 (s, 1H), 7.60 (s, 1H), 7.48 - 7.38 (m, 2H), 7.05 (d, J = 8.6 Hz, 2H), 6.89 (d, J = 8.8 Hz, 2H), 4.34 (q, J = 6.8 Hz, 1H), 3.99 - 3.86 (m, 4H), 3.73 (dd, J = 4.8, 10.8 Hz, 1H), 3.30 - 3.26 (m, 1H), 3.24 (s, 3H), 3.06 - 3.01 (m, 2H), 2.78 - 2.70 (m, 2H), 2.69 - 2.59 (m, 1H), 2.49 - 2.43 (m, 2H), 2.39 - 2.32 (m, 3H), 2.20 - 2.08 (m, 1H), 2.05 - 1.95 (m, 1H), 1.77 - 1.67 (m, 2H), 1.47 - 1.40 (m, 2H), 1.39 - 1.31 (m, 6H), 1.27 - 1.12 (m, 7H), 0.88 - 0.73 (m, 2H).

Example 64. Synthesis of N-(4-(2-(4-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperazin-1-yl)ethyl)piperidin-1-yl)-4-(((R)-7-ethyl-8-isopropyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzamide (Compound 64)

Step 1. Synthesis of tert-butyl (4-(2-(4-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperazin-1-yl)ethyl)piperidin-1-yl)carbamate (2)

To a solution of 3-(4-(piperazin-1-yl)phenyl)piperidine-2,6-dione (3.00 g, 9.68 mmol, HCl) and tert-butyl (4-(2-oxoethyl)piperidin-1-yl)carbamate (3.52 g, 14.53 mmol) in DCM (50 mL) were added TEA (4.90 g, 48.42 mmol) and MgSO ₄ (3.50 g, 29.05 mmol). The mixture was stirred at 20 °C for 1 h, after which NaBH(OAc) ₃ (5.13 g, 24.21 mmol) was added, and the mixture was stirred at 20 °C for 16 h. The desired mass peak (~67%) was confirmed by LCMS. The reaction mixture was diluted with water (30 mL), adjusted to pH= ₉ with saturated NaHCO3, extracted with DCM (100 mL x 3), and the combined organic layer was washed with brine (30 mL x 3), dried _{over Na2SO4} , filtered, and concentrated under reduced pressure. The residue was triturated with EtOAc (30 mL) at 20 °C for 10 min to obtain the title compound (2.70 g, 5.19 mmol, 53.57% yield, 96% purity) as a pale yellow solid. MS(M+H) ⁺ =500.4.

Step 2. Synthesis of 3-(4-(4-(2-(1-aminopiperidin-4-yl)ethyl)piperazin-1-yl)phenyl)piperidine-2,6-dione (3)

The title compound (296 mg, 576.38 μmol, 99.99% yield, TFA) was obtained as a brown oil by a similar method to step 2 of Example 32. MS(M+H) ⁺ = 400.2.

Step 3. Synthesis of N-(4-(2-(4-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperazin-1-yl)ethyl)piperidin-1-yl)-4-(((R)-7-ethyl-8-isopropyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzamide (Compound 64)

The title compound (131.4 mg, 164.55 μmol, 28.55% yield, 97.8% purity, 3TFA) was obtained as a white or yellow solid by a similar method as step 3 of Example 59. MS(M+H) ⁺ = 781.4

¹ H NMR (400 MHz, DMSO- d ₆ ) δ = 10.80 (s, 1H), 9.70 - 9.54 (m, 2H), 8.14 - 8.02 (m, 1H), 7.81 (s, 1H), 7.55 - 7.43 (m, 2H), 7.12 (d, J = 8.8 Hz, 2H), 6.98 (d, J = 8.8 Hz, 2H), 4.51 - 4.40 (m, 2H), 3.93 (s, 3H), 3.88 - 3.80 (m, 2H), 3.79 - 3.73 (m, 1H), 3.67 - 3.55 (m, 2H), 3.24 - 3.22 (m, 3H), 3.22 - 3.17 (m, 2H), 3.17 - 3.05 (m, 4H), 3.02 - 2.90 (m, 2H), 2.86 - 2.73 (m, 2H), 2.73 - 2.55 (m, 1H), 2.22 - 2.10 (m, 1H), 2.09 - 1.96 (m, 1H), 1.96 - 1.87 (m, 1H), 1.83 - 1.72 (m, 3H), 1.69 - 1.62 (m, 2H), 1.42 - 1.27 (m, 10H), 0.76 (t, J = 7.2 Hz, 3H).

Example 65. Synthesis of 4-(((R)-7,8-diethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(2-(4-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperazin-1-yl)ethyl)piperidin-1-yl)-3-methoxybenzamide (Compound 65)

The title compound (481.1 mg, 540.65 μmol, 46.31% yield, 99% purity, TFA salt) was obtained as a white solid by a similar method to step 9 of Example 12. MS(M+H) ⁺ = 767.5

^1H NMR (400 MHz, DMSO-d ₆ ) δ = 10.79 (s, 1H), 9.89 (m, 1H), 9.43 (br s, 1H), 8.12 (br d, J = 8.8 Hz, 1H), 7.83 (s, 1H), 7.60 - 7.44 (m, 2H), 7.13 (d, J = 8.6 Hz, 2H), 6.99 (d, J = 8.8 Hz, 2H), 4.57 (t, J = 4.4 Hz, 1H), 4.03 - 3.88 (m, 4H), 3.87 - 3.72 (m, 3H), 3.68 - 3.61 (m, 2H), 3.49 - 3.41 (m, 1H), 3.29 - 3.21 (m, 5H), 3.18 - 3.09 (m, 4H), 3.05 - 2.93 (m, 2H), 2.91 - 2.81 (m, 2H), 2.72 - 2.59 (m, 1H), 2.50 - 2.44 (m, 1H), 2.25 - 2.09 (m, 1H), 2.07 - 1.89 (m, 3H), 1.79 - 1.72 (m, 2H), 1.70 - 1.66 (m, 2H), 1.42 - 1.37 (m, 3H), 1.25 (t, J = 7.1 Hz, 3H), 0.76 (t, J = 7.4 Hz, 3H).

Example 66. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(2-(4-(4-((2,6-dioxopiperidin-3-yl)oxy)phenyl)piperazin-1-yl)ethyl)piperidin-1-yl)-3-methoxybenzamide (Compound 66)

Step 1. Synthesis of tert-butyl 4-(4-hydroxyphenyl)piperazine-1-carboxylate (2)

To a solution of 4-piperazin-1-ylphenol (3 g, 16.83 mmol) in MeOH (50 mL) was added Boc ₂ O (4.41 g, 20.20 mmol, 4.64 mL), and the mixture was stirred at 20 °C for 1 h. The peak of the target mass (98%) was confirmed by LCMS. The mixture was concentrated under reduced pressure to obtain the title compound (4.5 g, 16.17 mmol, 96.05% yield) as a brown solid. MS (M+H) ⁺ = 279.1

Step 2. Synthesis of tert-butyl 4-(4-((2,6-dioxopiperidin-3-yl)oxy)phenyl)piperazine-1-carboxylate (4)

The title compound (1.6 g, 4.11 mmol, 76.24% yield) was obtained as a yellow solid by a similar method to step 1 of Example 24. MS(M+H) ⁺ = 390.1

Step 3. Synthesis of 3-(4-(piperazin-1-yl)phenoxy)piperidine-2,6-dione (5)

A solution of tert-butyl 4-(4-((2,6-dioxopiperidin-3-yl)oxy)phenyl)piperazine-1-carboxylate (0.3 g, 770.33 μmol) in HCl/dioxane (2 M, 5 mL) was stirred at 20 °C for 1 h. The main peak of the desired mass was identified by LCMS. The mixture was concentrated under reduced pressure to obtain the title compound (250 mg, 767.37 μmol, 99.62% yield, HCl) as a yellow solid. MS(M+H) ⁺ = 290.2

Step 4. Synthesis of tert-butyl (4-(2-(4-(4-((2,6-dioxopiperidin-3-yl)oxy)phenyl)piperazin-1-yl)ethyl)piperidin-1-yl)carbamate (7)

The title compound (350 mg, 678.76 μmol, 88.45% yield) was obtained as a yellow solid by a similar method to step 1 of Example 59. MS (M+H) ⁺ = 516.3

Step 5. Synthesis of 3-(4-(4-(2-(1-aminopiperidin-4-yl)ethyl)piperazin-1-yl)phenoxy)piperidine-2,6-dione (8)

Synthesized in a similar manner to step 2 of Example 64 to afford the title compound as a yellow oil (61 mg, 115.19 μmol, 99.00% yield, TFA). MS(M+H) ⁺ = 416.2

Step 6. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(2-(4-(4-((2,6-dioxopiperidin-3-yl)oxy)phenyl)piperazin-1-yl)ethyl)piperidin-1-yl)-3-methoxybenzamide (Compound 66)

The title compound (13.6 mg, 16.48 μmol, 14.54% yield, 98% purity) was obtained as a white solid by a similar method to step 3 of Example 59. MS(M+H) ⁺ =809.5

^1H NMR (400 MHz, DMSO _- d6 ) δ = 10.89 (s, 1H), 9.23 (s, 1H), 8.42 (d, J = 8.9 Hz, 1H), 7.90 (s, 1H), 7.63 (s, 1H), 7.48 - 7.37 (m, 2H), 6.95 - 6.84 (m, 4H), 5.02 (dd, J = 4.9, 10.4 Hz, 1H), 4.47 - 4.39 (m, 1H), 4.33 (q, J = 6.6 Hz, 1H), 3.94 (s, 3H), 3.24 (s, 3H), 3.07 - 2.97 (m, 6H), 2.81 - 2.71 (m, 2H), 2.71 - 2.64 (m, 1H), 2.63 - 2.57 (m, 1H), 2.43 - 2.31 (m, 3H), 2.22 - 2.15 (m, 1H), 2.15 - 2.07 (m, 1H), 2.06 - 1.99 (m, 1H), 1.97 - 1.88 (m, 1H), 1.85 - 1.76 (m, 4H), 1.75 - 1.71 (m, 2H), 1.66 - 1.62 (m, 2H), 1.49 - 1.40 (m, 2H), 1.37 - 1.31 (m, 3H), 1.24 (d, J = 6.6 Hz, 4H), 1.22 - 1.16 (m, 1H), 0.89 - 0.76 (m, 1H).

Example 67. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(2-(4-(4-((2,6-dioxopiperidin-3-yl)amino)phenyl)piperazin-1-yl)ethyl)piperidin-1-yl)-3-methoxybenzamide (Compound 67)

The title compound (20.4 mg, 25.00 μmol, 15.82% yield, 99% purity) was obtained as a white solid by a similar method to step 3 of Example 59. MS(M+H) ⁺ =808.5

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.92 (br s, 1H), 9.31 - 9.17 (m, 1H), 8.43 (d, J = 9.2 Hz, 1H), 7.91 (s, 1H), 7.64 (s, 1H), 7.45 - 7.36 (m, 2H), 6.82 - 6.70 (m, 2H), 6.64 - 6.54 (m, 2H), 5.39 (d, J = 6.8 Hz, 1H), 4.48 - 4.39 (m, 1H), 4.36 - 4.29 (m, 1H), 4.22 - 4.09 (m, 1H), 3.94 (s, 3H), 3.24 (s, 3H), 3.02 - 2.89 (m, 6H), 2.79 - 2.67 (m, 3H), 2.63 - 2.53 (m, 2H), 2.49 - 2.45 (m, 2H), 2.39 - 2.30 (m, 2H), 2.14 - 1.92 (m, 3H), 1.87 - 1.54 (m, 10H), 1.47 - 1.38 (m, 2H), 1.34 - 1.26 (m, 3H), 1.23 (d, J = 6.6 Hz, 3H)

Example 68. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(2-(4-(4-((2,6-dioxopiperidin-3-yl)amino)phenyl)piperazin-1-yl)ethyl)piperidin-1-yl)-3-(2-hydroxyethoxy)benzamide (Compound 68)

Step 1. Synthesis of tert-butyl (4-(2-(4-(4-((2,6-dioxopiperidin-3-yl)amino)phenyl)piperazin-1-yl)ethyl)piperidin-1-yl)carbamate (3)

To a solution of 3-((4-(piperazin-1-yl)phenyl)amino)piperidine-2,6-dione (300 mg, 923.63 μmol, HCl) in DCM (10 mL) and DMF (2 mL) were added tert-butyl (4-(2-oxoethyl)piperidin-1-yl)carbamate (202 mg, 834.04 μmol) and TEA (436.20 mg, 4.31 mmol, 600 μL), and the mixture was stirred at 20 °C for 1 h. Then, NaBH(OAc) ₃ (600 mg, 2.83 mmol) was added to the mixture at 0 °C, and the mixture was stirred at 20 °C for 15 h. The peak of the target mass (73%) was confirmed by LCMS. To the reaction mixture were added H ₂ O (15 mL) and DCM (20 mL), and then NaHCO ₃ (sat. aq, 15 mL) was added to adjust the pH to 9. The mixture was extracted with DCM (30 mL × 2), and the combined organic layer was washed with brine (30 mL × 2), dried over Na ₂ SO ₄ , filtered, and the filtrate was concentrated under reduced pressure. The residue was purified by prep-HPLC (column: Phenomenex Luna C18 150 x 25 mm x10 μm; mobile phase: [H ₂ O (0.1% TFA) -ACN]; gradient: 0% - 25% B over 15.0 min; column Temp: 30 °C), and the eluate was lyophilized to obtain the title compound (260 mg, 505.19 μmol, 54.70% yield) as a pale yellow solid. MS(M+H) ⁺ =515.4

Step 2. Synthesis of 3-((4-(4-(2-(1-aminopiperidin-4-yl)ethyl)piperazin-1-yl)phenyl)amino)piperidine-2,6-dione (4)

The title compound (160 mg, crude, TFA) was obtained as a pale yellow oil by a similar method to step 2 of Example 32. MS(M+H) ⁺ = 415.3

Step 3. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(2-(4-(4-((2,6-dioxopiperidin-3-yl)amino)phenyl)piperazin-1-yl)ethyl)piperidin-1-yl)-3-(2-hydroxyethoxy)benzamide (Compound 68)

The title compound (22.4 mg, 26.46 μmol, 16.69% yield, 99% purity) was obtained as a white solid by a similar method to step 3 of Example 59. MS(M+H) ⁺ = 838.5

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.93 - 10.62 (m, 1H), 9.23 (s, 1H), 8.43 (d, J = 8.8 Hz, 1H), 8.08 (s, 1H), 7.91 (s, 1H), 7.46 - 7.37 (m, 2H), 6.75 (d, J = 8.9 Hz, 2H), 6.61 (d, J = 8.9 Hz, 2H), 5.39 (d, J = 7.1 Hz, 1H), 4.49 - 4.38 (m, 1H), 4.36 - 4.28 (m, 1H), 4.19 - 4.08 (m, 3H), 3.79 (t, J = 4.5 Hz, 2H), 3.39 - 3.36 (m, 1H), 3.25 (s, 3H), 3.02 - 2.88 (m, 6H), 2.79 - 2.64 (m, 3H), 2.60 - 2.52 (m, 2H), 2.48 - 2.42 (m, 2H), 2.36 - 2.31 (m, 2H), 2.14 - 1.92 (m, 3H), 1.86 - 1.51 (m, 10H), 1.46 - 1.38 (m, 2H), 1.34 - 1.26 (m, 3H), 1.24 (d, J = 6.7) Hz, 3H)

Examples 69 & 70. N-(4-(2-(4-(4-((2,6-dioxopiperidin-3-yl)amino)-2-fluorophenyl)piperazin-1-yl)ethyl)piperidin-1-yl)-4-(((R)-7-ethyl-8-isopropyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzamide (Compound 69) and Synthesis of 4-(((R)-7,8-diethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(2-(4-(4-((2,6-dioxopiperidin-3-yl)amino)-2-fluorophenyl)piperazin-1-yl)ethyl)piperidin-1-yl)-3-methoxybenzamide (Compound 70)

Step 1. Synthesis of tert-butyl 4-(4-((2,6-dioxopiperidin-3-yl)amino)-2-fluorophenyl)piperazine-1-carboxylate (3)

A solution of tert-butyl 4-(4-amino-2-fluorophenyl)piperazine-1-carboxylate (3 g, 10.16 mmol), 3-bromopiperidine-2,6-dione (4.88 g, 25.39 mmol), TBAI (375.18 mg, 1.02 mmol), and NaHCO ₃ (3.41 g, 40.63 mmol, 1.58 mL) in ACN (10 mL) was stirred at 80 °C for 60 h. The desired mass peak was confirmed by LCMS. The mixture was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (40 g SepaFlash® silica flash column, eluent of 50–80% EtOAc/Petroleum ether gradient @ 100 mL/min) to give the title compound (3.47 g, 8.54 mmol, 84.05% yield) as a blue solid. MS(M+H) ⁺ = 407.1

Step 2. Synthesis of 3-((3-fluoro-4-(piperazin-1-yl)phenyl)amino)piperidine-2,6-dione (4)

The title compound (1.7 g, crude, HCl salt) was obtained as a blue solid by a similar method to step 3 of Example 21. MS(M+H) ⁺ = 307.2

Step 3. Synthesis of tert-butyl (4-(2-(4-(4-((2,6-dioxopiperidin-3-yl)amino)-2-fluorophenyl)piperazin-1-yl)ethyl)piperidin-1-yl)carbamate (6)

The title compound as a blue solid (890 mg, 1.52 mmol, 30.66% yield, 91% purity) and another batch of the title compound as a blue solid (670 mg, 1.17 mmol, 23.59% yield, 93% purity) were obtained by a similar method as step 1 of Example 64. MS(M+H) ⁺ = 533.4

Step 4. Synthesis of 3-((4-(4-(2-(1-aminopiperidin-4-yl)ethyl)piperazin-1-yl)-3-fluorophenyl)amino)piperidine-2,6-dione (7)

The title compound (620 mg, crude, TFA salt) as a blue oil was obtained by a similar method to step 2 of Example 32. MS(M+H) ⁺ = 433.2

Step 5. Synthesis of N-(4-(2-(4-(4-((2,6-dioxopiperidin-3-yl)amino)-2-fluorophenyl)piperazin-1-yl)ethyl)piperidin-1-yl)-4-(((R)-7-ethyl-8-isopropyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzamide (Compound 69)

The title compound (204.21 mg, 169.58 μmol, 29.90% yield, 96% purity, 3TFA salt) was obtained as a gray solid by a similar method to step 3 of Example 64. MS(M+H) ⁺ = 814.5

SFC Method details: "Column: (S, S) Whelk-O ₁ 50Х4.6mm ID, 3.5um mobile phase: Phase A for CO ₂ , and Phase B for EtOH+ACN (0.05%DEA); Gradient elution: 60% EtOH+ACN (0.05% DEA) in CO ₂ Flow rate: 3mL/min; Detector: PDA Column Temp: 35C;Back Pressure: 100Bar"

¹ H NMR (400 MHz, DMSO- d ₆ ) δ = 10.80 (s, 1H), 9.75 - 9.44 (m, 2H), 9.38 - 9.06 (m, 1H), 8.12 - 8.00 (m, 1H), 7.81 (s, 1H), 7.56 - 7.43 (m, 2H), 6.89 (br t, J = 9.4 Hz, 1H), 6.55 (br dd, J = 2.3, 15.0 Hz, 1H), 6.46 (br d, J = 8.7 Hz, 1H), 4.52 - 4.41 (m, 2H), 4.29 (br dd, J = 4.5, 11.3 Hz, 1H), 3.93 (s, 3H), 3.57 (br d, J = 10.6 Hz, 2H), 3.33 - 3.05 (m, 11H), 3.00 - 2.91 (m, 2H), 2.86 - 2.68 (m, 2H), 2.62 - 2.53 (m, 1H), 2.47 - 2.39 (m, 1H), 2.12 - 2.02 (m, 1H), 1.96 - 1.71 (m, 5H), 1.64 (br d, J = 3.1 Hz, 2H), 1.36 (br t, J = 6.6 Hz, 9H), 0.76 (t, J = 7.5 Hz, 3H).

Step 6. Synthesis of 4-(((R)-7,8-diethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(2-(4-(4-((2,6-dioxopiperidin-3-yl)amino)-2-fluorophenyl)piperazin-1-yl)ethyl)piperidin-1-yl)-3-methoxybenzamide (Compound 70)

The title compound (208.14 mg, 178.61 μmol, 32.78% yield, 98% purity, 3TFA salt) was obtained as a yellow solid by a similar method to step 3 of Example 64. MS(M+H) ⁺ = 800.5

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.79 (s, 1H), 9.80 - 9.13 (m, 3H), 8.13 (br d, J = 8.8 Hz, 1H), 7.80 (s, 1H), 7.57 - 7.43 (m, 2H), 6.89 (t, J = 9.4 Hz, 1H), 6.65 - 6.42 (m, 2H), 4.56 (br t, J = 4.2 Hz, 1H), 4.34 - 4.24 (m, 1H), 4.00 - 3.84 (m, 4H), 3.57 (br d, J = 10.8 Hz, 2H), 3.49 - 3.38 (m, 1H), 3.32 - 3.05 (m, 11H), 3.01 - 2.91 (m, 2H), 2.85 - 2.69 (m, 2H), 2.62 - 2.52 (m, 2H), 2.13 - 2.03 (m, 1H), 1.99 - 1.81 (m, 3H), 1.79 - 1.70 (m, 2H), 1.69 - 1.59 (m, 2H), 1.36 (br s, 3H), 1.24 (br t, J = 7.0 Hz, 3H), 0.75 (t, J = 7.5 Hz, 3H).

Examples 71 & 72. 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(2-(4-(4-((2,6-dioxopiperidin-3-yl)amino)-2-fluoro-5-methoxyphenyl)piperazin-1-yl)ethyl)piperidin-1-yl)-2-fluoro-5-methoxybenzamide (Compound 71) and Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(2-(4-(4-((2,6-dioxopiperidin-3-yl)amino)-2-fluoro-5-methoxyphenyl)piperazin-1-yl)ethyl)piperidin-1-yl)-3-methoxybenzamide (Compound 72)

1. Synthesis of methyl (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-2-fluoro-5-methoxybenzoate (3)

To a solution of (R) _-2 -chloro-8-cyclopentyl-7-ethyl-5-methyl-7,8-dihydropteridin-6(5H)-one (2.7 g, 9.16 mmol) and methyl 4-amino-2-fluoro-5-methoxybenzoate (2.37 g, 11.91 mmol) in H 2 O (40 mL) and EtOH (10 mL) was added HCl (12 M, 1.53 mL), and the mixture was stirred at 100 °C for 16 h. The peak of the target mass (37%) was identified by LCMS. The mixture was cooled and filtered, and the filter cake was collected to give the title compound (1.3 g, 2.84 mmol, 31.02% yield) as a white solid. MS(M+H) ⁺ = 458.2.

Step 2. Synthesis of (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-2-fluoro-5-methoxybenzoic acid (4)

To a solution of methyl (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-2-fluoro-5-methoxybenzoate (1.3 g, 2.84 mmol) in THF (10 mL) and MeOH (10 mL) was added NaOH (2 M, 7.10 mL), and the mixture was stirred at 25 °C for 2 h. The peak of the desired mass (96%) was confirmed by LCMS. The mixture was concentrated under reduced pressure to remove the solvent. To the residue, H ₂ O (50 mL) and HCl solution (12 M) were added until pH<3, and the resulting mixture was filtered and the filter cake was washed with H ₂ O (50 mL). The filter cake was collected to obtain the title compound as a white solid (1.2 g, 2.52 mmol, 88.56% yield, 93% purity). MS(M+H) ⁺ = 444.1.

Step 3. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(2-(4-(4-((2,6-dioxopiperidin-3-yl)amino)-2-fluoro-5-methoxyphenyl)piperazin-1-yl)ethyl)piperidin-1-yl)-2-fluoro-5-methoxybenzamide (Compound 71)

The title compound (518.9 mg, 578.49 μmol, 21.38% yield, 99% purity) was obtained as a brown solid by a similar method to step 3 of Example 64. MS(M+H) ⁺ =888.4.

^1H NMR (400 MHz, DMSO-d ₆ ) δ = 10.85 (s, 1H), 8.95 (s, 1H), 8.37 (d, J = 13.3 Hz, 1H), 7.89 (s, 1H), 7.68 (s, 1H), 7.13 (d, J = 6.5 Hz, 1H), 6.67 - 6.52 (m, 2H), 5.22 - 4.97 (m, 1H), 4.45 - 4.33 (m, 1H), 4.31 - 4.23 (m, 2H), 3.94 - 3.88 (m, 3H), 3.80 (s, 3H), 3.26 (s, 3H), 3.09 - 2.98 (m, 2H), 2.98 - 2.89 (m, 3H), 2.87 - 2.73 (m, 2H), 2.71 - 2.62 (m, 2H), 2.63 - 2.56 (m, 3H), 2.47 - 2.23 (m, 3H), 2.15 - 2.02 (m, 2H), 1.98 - 1.50 (m, 14H), 1.48 - 1.28 (m, 4H), 0.77 (t, J = 7.4 Hz, 3H).

Step 4. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(2-(4-(4-((2,6-dioxopiperidin-3-yl)amino)-2-fluoro-5-methoxyphenyl)piperazin-1-yl)ethyl)piperidin-1-yl)-3-methoxybenzamide (Compound 72)

The title compound (417.7 mg, 470.50 μmol, 25.58% yield, 98% purity) was obtained as a brown solid by a similar method to step 3 of Example 64. MS(M+H) ⁺ =870.4.

^1H NMR (400 MHz, DMSO-d ₆ ) δ = 10.85 (s, 1H), 9.24 (s, 1H), 8.42 (d, J = 8.8 Hz, 1H), 7.85 (s, 1H), 7.60 (s, 1H), 7.47 - 7.37 (m, 2H), 6.67 - 6.50 (m, 2H), 5.10 (d, J = 6.1 Hz, 1H), 4.36 (d, J = 8.1 Hz, 1H), 4.30 - 4.19 (m, 2H), 3.94 (s, 3H), 3.80 (s, 3H), 3.25 (s, 3H), 3.05 - 2.88 (m, 6H), 2.86 - 2.73 (m, 3H), 2.61 - 2.51 (m, 5H), 2.45 - 2.29 (m, 2H), 2.20 - 2.10 (m, 1H), 2.08 - 1.99 (m, 1H), 1.97 - 1.85 (m, 3H), 1.84 - 1.70 (m, 6H), 1.69 - 1.59 (m, 3H), 1.51 - 1.39 (m, 2H), 1.38 - 1.30 (m, 3H), 0.77 (t, J = 7.4 Hz, 3H).

Example 73. Synthesis of 4-(((R)-7,8-diethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(2-(4-(4-((2,6-dioxopiperidin-3-yl)amino)-2-fluoro-5-methoxyphenyl)piperazin-1-yl)ethyl)piperidin-1-yl)-2-fluoro-5-methoxybenzamide (Compound 73)

Step 1. Synthesis of (R)-4-((7,8-diethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-2-fluoro-5-methoxybenzoic acid (3)

To a solution of (R)-2-chloro-7,8-diethyl-5-methyl-7,8-dihydropteridin-6(5H)-one (1.1 g, 4.32 mmol), 4-amino-2-fluoro-5-methoxybenzoic acid (1.21 g, 6.54 mmol) and _K2CO3 ( _1.80 g, 13.05 mmol) in t-BuOH (20 mL) were added _Pd2 (dba) ₃ (79.09 mg, 86.37 μmol) and XPhos (61.76 mg, 129.56 μmol) under _N2 , and the mixture was stirred at 100 °C under _CN2 for 14 h _. LCMS confirmed the remaining starting material and the peak of the target mass (30%). Additionally, t-BuOH (30 mL), Pd ₂ (dba) ₃ (79.09 mg, 86.37 μmol), and XPhos (61.76 mg, 129.56 μmol) were added under N ₂ , and the mixture was stirred at 100 °C under CN ₂ for 14 h. The peak of the target mass (72%) was confirmed by LCMS. The mixture was concentrated under reduced pressure, and the product was diluted with water (50 mL), and 1 N HCl (60 mL) was slowly poured. The suspension was then filtered. The filter cake was washed with water (30 mL) and dried under reduced pressure. The product was diluted with EtOAc (80 mL), and the suspension was stirred at 15 °C for 1 h. The suspension was filtered, and the filter cake was washed with EtOAc (10 mL). The filter cake was collected and dried to give the title compound as a gray solid (1.77 g, 4.30 mmol, 99.57% yield, 98% purity). MS(M+H) ⁺ = 404.2.

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 9.62 - 9.36 (m, 1H), 8.19 (d, J = 13.2 Hz, 1H), 7.93 (s, 1H), 7.43 (d, J = 6.5 Hz, 1H), 4.58 (t, J = 4.2 Hz, 1H), 3.93 (s, 3H), 3.92 - 3.84 (m, 1H), 3.54 - 3.48 (m, 2H), 3.22 (s, 3H), 2.00 - 1.90 (m, 2H), 1.28 (t, J = 7.0 Hz, 3H), 0.75 (t, J = 7.4 Hz, 3H)

Step 2. Synthesis of 4-(((R)-7,8-diethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(2-(4-(4-((2,6-dioxopiperidin-3-yl)amino)-2-fluoro-5-methoxyphenyl)piperazin-1-yl)ethyl)piperidin-1-yl)-2-fluoro-5-methoxybenzamide (Compound 73)

The title compound (1424.6 mg, 1.16 mmol, 46.84% yield, 97% purity, 3TFA salt) was obtained as a gray solid by a similar method to step 3 of Example 64. MS(M+H) ⁺ =848.5

¹ H NMR (400 MHz, DMSO- d ₆ ) δ = 10.58 (s, 1H), 9.49 - 9.06 (m, 1H), 8.82 - 8.68 (m, 1H), 8.36 - 8.18 (m, 1H), 8.07 - 7.94 (m, 1H), 7.81 (s, 1H), 7.26 - 7.08 (m, 1H), 6.69 - 6.49 (m, 2H), 4.39 - 4.35 (m, 1H), 4.26 (dd, J = 5.0, 12.0 Hz, 1H), 4.00 - 3.94 (m, 1H), 3.93 (s, 3H), 3.82 (s, 3H), 3.64 - 3.44 (m, 2H), 3.43 - 2.95 (m, 15H), 2.85 - 2.66 (m, 3H), 2.62 - 2.54 (m, 1H), 2.22 - 2.13 (m, 1H), 1.99 - 1.80 (m, 3H), 1.78 - 1.62 (m, 4H), 1.43 - 1.33 (m, 2H), 1.27 (t, J = 7.1 Hz, 3H), 0.79 (t, J = 7.4 Hz, 3H).

Example 74. Synthesis of 5-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(2-(4-(4-((2,6-dioxopiperidin-3-yl)amino)-2-fluoro-5-methoxyphenyl)piperazin-1-yl)ethyl)piperidin-1-yl)-4-methoxypicolinamide (Compound 74)

Step 1. Synthesis of (R)-2-amino-8-cyclopentyl-7-ethyl-5-methyl-7,8-dihydropteridin-6(5H)-one (2)

A mixture of (R)-2-chloro-8-cyclopentyl-7-ethyl-5-methyl-7,8-dihydropteridin-6(5H)-one (2.30 g, 7.80 mmol), tert-butyl carbamate (1.83 g, 15.60 mmol), XPhos (744 mg, 1.56 mmol), Pd ₂ (dba) ₃ (714.5 mg, 780.25 μmol), and Cs ₂ CO ₃ (5.08 g, 15.60 mmol) in dioxane (40 mL) was degassed and purged three times with N ₂ , and the mixture was stirred at 100 °C under CN ₂ for 16 h. The peak of the target mass (39%) was identified by LCMS. The reaction mixture was concentrated under reduced pressure, and the residue was purified by flash silica gel chromatography (ISCO®; 40 g SepaFlash® silica flash column, Eluent of 80–90% EtOAc/Petroleum ether gradient @ 60 mL/min) to give the title compound (1.00 g, 3.56 mmol, 45.62% yield, 98% purity) as a white-yellow solid. MS(M+H) ⁺ = 276.2.

Step 2. Synthesis of methyl (R)-5-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-4-methoxypicolinate (4)

The title compound (1.40 g, 3.18 mmol, 87.51% yield) was obtained as a yellow solid by a similar method to step 1 of Example 18. MS(M+H) ⁺ = 441.2.

Step 3. Synthesis of (R)-5-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-4-methoxypicolinic acid (5)

To a solution of methyl (R)-5-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-4-methoxypicolinate (1.40 g, 3.18 mmol) in MeOH (10 mL) and THF (10 mL) was added NaOH (2 M, 3.2 mL). The mixture was stirred at 25 °C for 2 h. The peak of the target mass (84%) was identified by LCMS. The mixture was concentrated under reduced pressure to remove the solvent, and the pH was adjusted to 7 with HCl (1 M). The suspension was filtered, and the filter cake was collected and dried under reduced pressure to obtain the title compound (1.40 g, 2.82 mmol, 88.83% yield, 86% purity) as a pale yellow solid. MS(M+H) ⁺ = 427.2.

Step 4. Synthesis of 5-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(2-(4-(4-((2,6-dioxopiperidin-3-yl)amino)-2-fluoro-5-methoxyphenyl)piperazin-1-yl)ethyl)piperidin-1-yl)-4-methoxypicolinamide (Compound 74)

To a solution of (R)-5-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-4-methoxypicolinic acid (1.30 g, 2.62 mmol) in DMF (20 mL) were added HATU (1.06 g, 2.80 mmol) and DIPEA (1.45 g, 11.19 mmol), and the mixture was stirred at 25 °C for 1 h. Then, 3-((4-(4-(2-(1-aminopiperidin-4-yl)ethyl)piperazin-1-yl)-5-fluoro-2-methoxyphenyl)amino)piperidine-2,6-dione (2.15 g, 3.73 mmol, TFA salt) was added, and the mixture was stirred at 25 °C for 14 h. The target mass peak (70%) was confirmed by LCMS. The reaction mixture was diluted with water (50 mL) and extracted with EtOAc (100 mL x 3). The mixed organic layer was washed with a saturated NaHCO ₃ solution (50 mL x 3) and brine (50 mL x 2), dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure to obtain the residue. The residue was purified by flash silica gel chromatography (ISCO®; 40 g SepaFlash® silica flash column, Eluent of 0–10% MeOH/DCM @ 100 mL/min) followed by prep-HPLC (neutral condition, column: Waters Xbridge C18 150 x 50 mm x 10 um; mobile phase: [water (NH ₄ HCO ₃ ) - ACN]; gradient: 38% - 68% B over 10 min), and the eluate was lyophilized to give the title compound (1.00 g, 1.13 mmol, 30.33% yield, 98.1% purity) as a white solid. MS(M+H) ⁺ =871.6.

¹ H NMR (400 MHz, DMSO- d ₆ ) δ = 10.84 (s, 1H), 9.26 (s, 1H), 9.23 (s, 1H), 7.81 (s, 1H), 7.78 (s, 1H), 7.60 (s, 1H), 6.61 (d, J = 8.0 Hz, 1H), 6.54 (d, J = 14.0 Hz, 1H), 5.08 (d, J = 6.0 Hz, 1H), 4.32 - 4.19 (m,3H), 3.98 (s, 3H), 3.79 (s, 3H), 3.24 (m,3H), 3.00 - 2.94 (m, 2H), 2.94 - 2.87 (m, 4H), 2.85 - 2.75 (m, 1H), 2.73 - 2.64 (m, 2H), 2.58 - 2.51 (m, 4H), 2.38 - 2.32 (m, 2H), 2.17 - 2.08 (m, 1H), 2.00 - 1.88 (m, 2H), 1.88 - 1.81 (m, 2H), 1.81 - 1.47 (m, 10H), 1.46 - 1.38 (m, 2H), 1.38 - 1.27 (m, 3H) 0.76 (t, J = 7.6 Hz, 3H).

Example 75. Synthesis of 5-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(2-(4-(4-((2,6-dioxopiperidin-3-yl)amino)-3-fluoro-2-methoxyphenyl)piperazin-1-yl)ethyl)piperidin-1-yl)-4-methoxypicolinamide (Compound 75)

The title compound (676.1 mg, 768.46 μmol, 27.31% yield, 99% purity) was obtained as a white solid by a similar method to step 4 of Example 74. MS(M+H) ⁺ =871.4.

^1H NMR (400 MHz, DMSO-d ₆ ) δ = 10.83 (s, 1H), 9.47 - 9.27 (m, 1H), 9.24 (s, 1H), 7.81 (d, J = 6.5 Hz, 2H), 7.60 (s, 1H), 6.69 - 6.54 (m, 1H), 6.52 - 6.43 (m, 1H), 5.43 - 5.16 (m, 1H), 4.36 - 4.14 (m, 3H), 3.99 (s, 3H), 3.84 (s, 3H), 3.34 (s, 3H), 3.08 - 2.81 (m, 6H), 2.77 - 2.64 (m, 3H), 2.62 - 2.55 (m, 6H), 2.40 - 2.31 (m, 1H), 2.14 - 1.92 (m, 3H), 1.89 - 1.81 (m, 2H), 1.80 - 1.61 (m, 7H), 1.59 - 1.40 (m, 4H), 1.38 - 1.24 (m, 3H), 0.76 (br t, J = 7.4 Hz, 3H).

Example 76. Synthesis of N-(4-(2-(4-(4-((2,6-dioxopiperidin-3-yl)amino)-2-fluoro-5-methoxyphenyl)piperazin-1-yl)ethyl)piperidin-1-yl)-5-(((R)-7-ethyl-8-isopropyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-4-methoxypicolinamide (Compound 76)

Step 1. Synthesis of methyl (R)-2-(isopropylamino)butanoate (2)

To a solution of methyl (R)-2-aminobutanoate hydrochloride (50 g, 325.51 mmol, HCl) and acetone (24.58 g, 423.16 mmol, 31.11 mL) in DCM (500 mL) were added NaOAc (26.70 g, 325.51 mmol) and NaBH(OAc) ₃ (103.48 g, 488.26 mmol) at 0 °C, and the mixture was stirred at 25 °C for 16 h. TLC (EtOAc:Petroleum ether=1:2) confirmed the formation of two new spots. The reaction mixture was quenched with saturated NaHCO ₃ (800 mL) and extracted with DCM (500 mL x 3). The organic layer was dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure to obtain the title compound (32.44 g, 203.74 mmol, 62.59% yield) as a yellow oil. MS(M+H) ⁺ = 160.1

Step 2. Synthesis of methyl (R)-2-((2-chloro-5-nitropyrimidin-4-yl)(isopropyl)amino)butanoate (4)

To a solution of methyl (R)-2-(isopropylamino)butanoate (32.44 g, 203.74 mmol) and 2,4-dichloro-5-nitropyrimidine (47.42 g, 244.48 mmol) in acetone (400 mL) was added K ₂ CO ₃ (42.24 g, 305.60 mmol) dropwise at 0 °C. The mixture was stirred at 20 °C for 16 h. The target mass peak (51%) was confirmed by LCMS. The reaction mixture was filtered and concentrated under reduced pressure to obtain a residue. The residue was purified by flash silica gel chromatography (330 g SepaFlash® silica flash column, eluent of 0–30% EtOAc/Petroleum ether gradient @ 200 mL/min) to give the title compound (18 g, 56.83 mmol, 27.89% yield) as a yellow solid. MS(M+H) ⁺ = 317.1

Step 3. Synthesis of (R)-2-chloro-7-ethyl-8-isopropyl-7,8-dihydropteridin-6(5H)-one (5)

To a solution of methyl (R)-2-((2-chloro-5-nitropyrimidin-4-yl)(isopropyl)amino)butanoate (17 g, 53.67 mmol) in AcOH (170 mL) was added Fe (11.99 g, 214.69 mmol). The mixture was stirred at 60 °C for 1 h. The peak of the target mass (93%) was identified by LCMS. The reaction mixture was filtered and concentrated under reduced pressure. The residue was diluted with H ₂ O (200 mL) and extracted with EtOAc (200 mL x 3). The organic layer was dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure to give the title compound (13 g, crude) as a brown solid. MS(M+H) ⁺ = 255.1

Step 4. Synthesis of (R)-2-chloro-7-ethyl-8-isopropyl-5-methyl-7,8-dihydropteridin-6(5H)-one (6)

To a solution of (R)-2-chloro-7-ethyl-8-isopropyl-7,8-dihydropteridin-6(5H)-one (6 g, 23.56 mmol) in DMF (60 mL) were added K ₂ CO ₃ (9.77 g, 70.67 mmol) and MeI (4.56 g, 32.13 mmol, 2 mL). The mixture was stirred at 20 °C for 12 h. TLC (EtOAc:Petroleum ether=1:1) confirmed the formation of two new spots. LCMS confirmed the peak of the target mass (67%). The reaction mixture was diluted with H ₂ O (200 mL) and extracted with EtOAc (250 mL x 2). The mixed organic layer was washed with brine (250 mL x 2), dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure to obtain a residue. The residue was purified by flash silica gel chromatography (40 g SepaFlash® silica flash column, eluent of 0–50% EtOAc/Petroleum ether gradient @ 100 mL/min) to obtain the title compound (5 g, 18.23 mmol, 77.40% yield, 98% purity) as a white solid. MS(M+H) ⁺ = 269.3

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 7.87 (s, 1H), 4.48 - 4.15 (m, 2H), 3.24 (s, 3H), 1.90 - 1.75 (m, 1H), 1.71 - 1.58 (m, 1H), 1.32 (d, J = 6.8 Hz, 6H), 0.73 (t, J = 7.5 Hz, 3H)

Step 5. Synthesis of (R)-2-amino-7-ethyl-8-isopropyl-5-methyl-7,8-dihydropteridin-6(5H)-one (7)

The title compound (2.2 g, 7.85 mmol, 70.35% yield, 89% purity) and the title compound (150 mg, 324.89 μmol, 2.91% yield, 54% purity) as a yellow oil were synthesized in a similar manner to step 1 of Example 74. MS(M+H) ⁺ = 250.1

Step 6. Synthesis of methyl (R)-5-((7-ethyl-8-isopropyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-4-methoxypicolinate (9)

The title compound as a yellow solid (1.8 g, 4.00 mmol, 45.28% yield, 92% purity) and the title compound as a yellow solid (480 mg, 1.03 mmol, 11.68% yield, 89% purity) were obtained by a similar method as step 1 of Example 18. MS(M+H) ⁺ = 415.1

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 9.52 (s, 1H), 7.86 (s, 1H), 7.79 (s, 1H), 7.66 (s, 1H), 4.62 - 4.52 (m, 1H), 4.30 (dd, J = 3.4, 7.5 Hz, 1H), 4.01 (s, 3H), 3.86 (s, 3H), 3.25 (s, 3H), 1.88 - 1.75 (m, 1H), 1.72 - 1.59 (m, 1H), 1.34 (dd, J = 6.8, 13.8 Hz, 6H), 0.76 (t, J = 7.5 Hz, 3H).

Step 7. Synthesis of (R)-5-((7-ethyl-8-isopropyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-4-methoxypicolinic acid (10)

The title compound (2 g, crude) was obtained as a yellow solid by a similar method to step 2 of Example 18. MS(M+H) ⁺ = 401.2

Step 8. Synthesis of 1,2-difluoro-4-methoxy-5-nitrobenzene (14)

The title compound (22.8 g, 120.56 mmol, 84.44% yield) was obtained as a yellow solid by a similar method to step 2 of Example 8. MS(M+H) ⁺ = 190.0

Step 9. Synthesis of tert-butyl 4-(2-fluoro-5-methoxy-4-nitrophenyl)piperazine-1-carboxylate (15)

To a solution of 1,2-difluoro-4-methoxy-5-nitrobenzene (22.8 g, 120.56 mmol) and tert-butyl piperazine-1-carboxylate (26.95 g, 144.67 mmol) in ACN (250 mL) was added K ₂ CO ₃ (49.99 g, 361.68 mmol), and the mixture was stirred at 20 °C for 16 h. TLC (Petroleum ether:EtOAc=3:1) confirmed the formation of a new spot. LCMS confirmed the peak of the target mass (78%). The reaction mixture was filtered, and the filtrate was concentrated under reduced pressure. The residue was triturated with EtOAc (150 mL) at 20 °C for 60 min and the filtrate was purified by flash silica gel chromatography (80 g SepaFlash® silica flash column, Eluent of 0–15% EtOAc/Petroleum ether gradient @ 200 mL/min) to give the title compound (31.8 g, 89.49 mmol, 74.23% yield) as a yellow solid. MS(M+H-100) ⁺ = 256.1

Step 10. Synthesis of tert-butyl 4-(4-amino-2-fluoro-5-methoxyphenyl)piperazine-1-carboxylate (16)

A mixture of tert-butyl 4-(2-fluoro-5-methoxy-4-nitrophenyl)piperazine-1-carboxylate (31.8 g, 89.49 mmol) in THF (320 mL) and MeOH (320 mL) was stirred at 20 °C until a clear solution became available. The H ₂ pressure regulator was adjusted to 1.0 MPa, the H ₂ flow rate was 80 mL/min, and the fixed bed (Pt/C, 12 g, 571.12 μmol, 1% purity) was heated to 45 °C. The solution was then pumped into the reactor (flow rate 1.2 mL/min). The target mass peak (99%) was confirmed by LCMS. After the reaction was completed, the mixture was washed with THF (100 mL). The mixture was concentrated under reduced pressure to obtain the title compound as a brown solid (28.5 g, 86.71 mmol, 96.90% yield, 99% purity). MS(M+H) ⁺ = 326.2

Step 11. Synthesis of tert-butyl 4-(4-((2,6-dioxopiperidin-3-yl)amino)-2-fluoro-5-methoxyphenyl)piperazine-1-carboxylate (17)

To a solution of tert-butyl 4-(4-amino-2-fluoro-5-methoxyphenyl)piperazine-1-carboxylate (10 g, 30.73 mmol) and 3-bromopiperidine-2,6-dione (8.85 g, 46.10 mmol) in ACN (20 mL) was added NaHCO ₃ (7.75 g, 92.20 mmol, 3.59 mL). The mixture was stirred at 80 °C for 38.5 h. The peak of the target mass (57%) was identified by LCMS. The reaction mixture was filtered, and the filter cake was dried under reduced pressure to obtain the title compound (13.1 g, 27.91 mmol, 90.82% yield, 93% purity) as a green solid. MS(M+H) ⁺ = 437.2

Step 12. Synthesis of 3-((5-fluoro-2-methoxy-4-(piperazin-1-yl)phenyl)amino)piperidine-2,6-dione (18)

To a solution of tert-butyl 4-(4-((2,6-dioxopiperidin-3-yl)amino)-2-fluoro-5-methoxyphenyl)piperazine-1-carboxylate (13.1 g, 30.01 mmol) in DCM (20 mL) was added HCl/dioxane (2 M, 200 mL). The mixture was stirred at 25 °C for 34 h. The peak of the target mass (93%) was confirmed by LCMS. The reaction mixture was concentrated under reduced pressure to obtain the title compound (16.8 g, crude, 6HCl) as a blue solid. MS(M+H) ⁺ = 337.0

Step 13. Synthesis of tert-butyl (4-(2-(4-(4-((2,6-dioxopiperidin-3-yl)amino)-2-fluoro-5-methoxyphenyl)piperazin-1-yl)ethyl)piperidin-1-yl)carbamate (20)

To a solution of tert-butyl (4-(2-oxoethyl)piperidin-1-yl)carbamate (2 g, 8.25 mmol) and 3-((5-fluoro-2-methoxy-4-(piperazin-1-yl)phenyl)amino)piperidine-2,6-dione (3.82 g, 6.88 mmol, 6HCl) in DCM (10 mL) were added NaBH(OAc) ₃ (2.19 g, 10.32 mmol), 4A MS (500 mg, 6.88 mmol), and TEA (2.09 g, 20.63 mmol, 2.87 mL). The mixture was stirred at 20 °C for 16 h. The peak of the target mass (89%) was identified by LCMS. The reaction mixture was filtered, the filtrate was diluted with H ₂ O (80 mL), and the mixture was extracted with EtOAc (100 mL x 2). The combined organic layer was washed with brine (150 mL), dried over Na ₂ SO ₄ , filtered, and the filtrate was concentrated under reduced pressure to obtain a residue. The residue was triturated with EtOAc at 20 °C for 60 min to obtain the title compound (2.3 g, 4.01 mmol, 58.24% yield, 98% purity) as a green solid. MS(M+H) ⁺ = 563.3

Step 14. Synthesis of 3-((4-(4-(2-(1-aminopiperidin-4-yl)ethyl)piperazin-1-yl)-5-fluoro-2-methoxyphenyl)amino)piperidine-2,6-dione (12)

The title compound (2 g, crude, TFA) as a blue oil was obtained by a similar method to step 2 of Example 32. MS(M+H) ⁺ = 463.2

Step 15. Synthesis of N-(4-(2-(4-(4-((2,6-dioxopiperidin-3-yl)amino)-2-fluoro-5-methoxyphenyl)piperazin-1-yl)ethyl)piperidin-1-yl)-5-(((R)-7-ethyl-8-isopropyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-4-methoxypicolinamide (Compound 76)

The title compound (670.3 mg, 785.35 μmol, 26.21% yield, 99% purity) was obtained as a white solid by a similar method to step 4 of Example 74. MS (M+H) ⁺ = 845.4

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.84 (br s, 1H), 9.39 - 9.25 (m, 2H), 7.82 (s, 1H), 7.73 (s, 1H), 7.60 (s, 1H), 6.68 - 6.49 (m, 2H), 5.08 (d, J = 6.8 Hz, 1H), 4.60 - 4.47 (m, 1H), 4.33 - 4.21 (m, 2H), 4.00 (s, 3H), 3.79 (s, 3H), 3.24 (s, 3H), 3.02 - 2.86 (m, 6H), 2.85 - 2.75 (m, 1H), 2.73 - 2.64 (m, 2H), 2.54 - 2.50 (m, 5H), 2.35 (t, J = 7.1 Hz, 2H), 2.19 - 2.07 (m, 1H), 2.00 - 1.86 (m, 1H), 1.84 - 1.57 (m, 4H), 1.48 - 1.38 (m, 2H), 1.32 (dd, J = 6.8, 14.6 Hz, 9H), 0.76 (t, J = 7.5 Hz, 3H).

Example 77. Synthesis of N-(4-(2-(4-(4-((2,6-dioxopiperidin-3-yl)amino)-3-fluoro-2-methoxyphenyl)piperazin-1-yl)ethyl)piperidin-1-yl)-5-(((R)-7-ethyl-8-isopropyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-4-methoxypicolinamide (Compound 77)

The title compound (1564.92 mg, 1.81 mmol, 58.80% yield, 97.7% purity) was obtained as a white solid by a similar method to step 4 of Example 74. MS(M+H) ⁺ =845.4

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.81 (s, 1H), 9.40 - 9.27 (m, 2H), 7.82 (s, 1H), 7.73 (s, 1H), 7.60 (s, 1H), 6.61 - 6.56 (m, 1H), 6.52 - 6.44 (m, 1H), 5.32 - 5.22 (m, 1H), 4.53 (td, J = 6.6, 13.4 Hz, 1H), 4.34 - 4.23 (m, 2H), 4.00 (s, 3H), 3.82 (s, 3H), 3.31 - 3.28 (m, 1H), 3.24 (s, 3H), 3.01 - 2.85 (m, 6H), 2.81 - 2.63 (m, 4H), 2.59 - 2.52 (m, 3H), 2.39 - 2.29 (m, 2H), 2.13 - 1.91 (m, 2H), 1.84 - 1.60 (m, 4H), 1.48 - 1.23 (m, 11H), 0.76 (t, J = 7.5 Hz, 3H)

Example 78. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(2-(4-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperazin-1-yl)ethyl)cyclohexyl)-3-methoxybenzamide (Compound 78)

Step 1. Synthesis of tert-butyl ((1r,4r)-4-(2-(4-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperazin-1-yl)ethyl)cyclohexyl)carbamate (2)

To a solution of 3-(4-piperazin-1-ylphenyl)piperidine-2,6-dione (0.4 g, 1.29 mmol, HCl salt) and tert-butyl ((1r,4r)-4-(2-oxoethyl)cyclohexyl)carbamate (311.60 mg, 1.29 mmol) in DCM (12 mL) and DMF (2 mL) were added TEA (783.93 mg, 7.75 mmol, 1.08 mL) and MgSO ₄ (233.13 mg, 1.94 mmol) at 20 °C. The mixture was stirred for 1 h. Then, NaBH(OAc) ₃ (820.97 mg, 3.87 mmol) was added at 20 °C, and the resulting mixture was stirred at 20 °C for 12 h. LCMS confirmed that the starting material was completely consumed and the peak of the target mass (62%) was observed. The reaction mixture was diluted with H ₂ O (30 mL) and extracted with DCM (30 mL x 4). The organic layer was washed with saturated NaHCO ₃ (30 mL x 3), dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure. The product was triturated with MTBE (15 mL) at 20 °C for 0.5 h and filtered. The filter cake was dried under reduced pressure to obtain the title compound (457 mg, 916.46 μmol, 70.98% yield) as a yellow solid. MS(M+H) ⁺ = 499.3

Step 2. Synthesis of 3-(4-(4-(2-((1r,4r)-4-aminocyclohexyl)ethyl)piperazin-1-yl)phenyl)piperidine-2,6-dione (3)

The title compound (0.4 g, crude, HCl salt) was obtained as a yellow solid by a similar method to step 4 of Example 60. MS(M+H) ⁺ = 399.4

Step 3. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(2-(4-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperazin-1-yl)ethyl)cyclohexyl)-3-methoxybenzamide (Compound 78)

The title compound (13.7 mg, 17.13 μmol, 8.81% yield, 99% purity) was obtained as a white solid by a similar method to step 3 of Example 59. MS(M+H) ⁺ = 792.4

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.78 (br s, 1H), 8.42 (d, J = 8.9 Hz, 1H), 8.03 (br d, J = 7.8 Hz, 1H), 7.90 (s, 1H), 7.62 (s, 1H), 7.52 - 7.41 (m, 2H), 7.04 (br d, J = 8.5 Hz, 2H), 6.88 (br d, J = 8.6 Hz, 2H), 4.42 (quin, J = 7.8 Hz, 1H), 4.35 - 4.27 (m, 1H), 3.94 (s, 3H), 3.72 (br dd, J = 4.8, 10.9 Hz, 2H), 3.23 (s, 3H), 3.10 (br s, 4H), 2.63 (ddd, J = 5.0, 11.3, 16.8 Hz, 1H), 2.44 (br d, J = 4.4 Hz, 1H), 2.35 (br t, J = 7.3 Hz, 2H), 2.19 - 2.07 (m, 1H), 2.05 - 1.97 (m, 2H), 1.92 (br d, J = 7.4 Hz, 1H), 1.88 - 1.76 (m, 7H), 1.68 - 1.58 (m, 2H), 1.43 - 1.29 (m, 5H), 1.22 (br d, J = 6.6 Hz, 3H), 1.17 (br s, 2H), 1.09 - 0.97 (m, 3H), 0.89 - 0.80 (m, 1H), 0.78 - 0.70 (m, 1H)

Example 79. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(1-(3-(4-(6-(2,6-dioxopiperidin-3-yl)pyridin-3-yl)piperazin-1-yl)propanoyl)piperidin-4-yl)-3-methoxybenzamide (Compound 79)

Step 1. Synthesis of tert-butyl 4-(2',6'-bis(benzyloxy)-[2,3'-bipyridin]-5-yl)piperazine-1-carboxylate (3)

The title compound (2 g, 3.37 mmol, 38.39% yield, 93% purity) was obtained as a white solid by a similar method to step 1 of Example 21. MS(M+H) ⁺ = 553.6

Step 2. Synthesis of tert-butyl 4-(6-(2,6-dioxopiperidin-3-yl)pyridin-3-yl)piperazine-1-carboxylate (4)

A mixture of Pd/C (462.14 mg, 10% purity) and Pd(OH) ₂ (1 g, 20% purity) in THF (15 mL) was slowly added to a solution of tert-butyl 4-(2',6'-bis(benzyloxy)-[2,3'-bipyridin]-5-yl)piperazine-1-carboxylate (2.4 g, 4.34 mmol) in THF (140 mL) under N ₂ , and the mixture was stirred at 25 °C under CH ₂ (50 Psi) for 48 h. LCMS showed that 47% of the reactant remained. A solution of Pd/C (1 g, 10% purity) and Pd(OH) ₂ (1 g, 20% purity) in THF (20 mL) was added to the reaction mixture under N ₂ , and the mixture was stirred at 25 °C under CH ₂ (50 Psi) for 14 h. LCMS confirmed the consumption of the starting material and the appearance of a peak of the desired mass. The mixture was filtered, the filter cake was washed with THF (200 mL), and the filtrate was concentrated under reduced pressure. The residue was triturated with MTBE (30 ml) at 25 °C for 60 min and repurified by flash silica gel chromatography (20 g SepaFlash® silica flash column, Eluent of 0–100% EtOAc/Petroleum ether gradient @ 40 mL/min) to give the title compound (0.9 g, 2.38 mmol, 54.80% yield, 99% purity) as a white solid. MS(M+H) ⁺ = 375.2.

Step 3. Synthesis of 3-(5-(piperazin-1-yl)pyridin-2-yl)piperidine-2,6-dione (5)

To a solution of tert-butyl 4-(6-(2,6-dioxopiperidin-3-yl)pyridin-3-yl)piperazine-1-carboxylate (0.9 g, 2.40 mmol) in DCM (10 mL) was added HCl/dioxane (2 M, 280 mL). The mixture was stirred at 25 °C for 38 h. LCMS confirmed the remaining tert-butyl 4-(6-(2,6-dioxopiperidin-3-yl)pyridin-3-yl)piperazine-1-carboxylate. The reaction mixture was concentrated under reduced pressure to obtain the title compound (900 mg, 1.94 mmol, 80.72% yield, 67% purity, HCl) as a white solid. MS(M+H) ⁺ = 275.2.

Step 4. Synthesis of tert-butyl (1-(3-(4-(6-(2,6-dioxopiperidin-3-yl)pyridin-3-yl)piperazin-1-yl)propanoyl)piperidin-4-yl)carbamate (7)

To a solution of 3-(5-(piperazin-1-yl)pyridin-2-yl)piperidine-2,6-dione (0.85 g, 3.10 mmol) and tert-butyl (1-(3-chloropropanoyl)piperidin-4-yl)carbamate (1.44 g, 4.96 mmol) in DMF (6 mL) were added DIPEA (1.20 g, 9.30 mmol, 1.62 mL) and KI (51.44 mg, 309.86 μmol). The mixture was stirred at 80 °C for 3 h. The desired mass peak was confirmed at 27% by LCMS. The residue was diluted with water (50 mL) and extracted with EtOAc (40 mL x 3). The combined organic layers were washed with brine (100 mL), dried over anhydrous Na ₂ SO ₄ , filtered, and concentrated under reduced pressure. The aqueous phase was DCM (40 mL x 3). The combined organic layers were dried over anhydrous Na ₂ SO ₄ , filtered, and concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (20 g SepaFlash® silica flash column, Eluent of 0–65% EtOAc/Petroleum ether gradient @ 85 mL/min) to afford the title compound as a brown solid (260 mg, 462.32 μmol, 14.92% yield, 94% purity) and the title compound as a brown solid (100 mg, 174.03 μmol, 5.62% yield, 92% purity). MS(M+H) ⁺ = 529.2.

Step 5. Synthesis of 3-(5-(4-(3-(4-aminopiperidin-1-yl)-3-oxopropyl)piperazin-1-yl)pyridin-2-yl)piperidine-2,6-dione (8)

The title compound (400 mg, crude, HCl) was obtained as a yellow solid by a similar method to step 3 of Example 29. MS(M+H) ⁺ = 429.3

Step 6. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(1-(3-(4-(6-(2,6-dioxopiperidin-3-yl)pyridin-3-yl)piperazin-1-yl)propanoyl)piperidin-4-yl)-3-methoxybenzamide (Compound 79)

The title compound (44 mg, 44.32 μmol, 5.89% yield, 95.7% purity, TFA) was obtained as a yellow solid by a similar method to step 3 of Example 59. MS(M+H) ⁺ =836.2.

¹ H NMR (400 MHz, DMSO- d ₆ ) δ = 10.85 (s, 1H), 9.85 - 9.66 (m, 1H), 8.37 - 8.23 (m, 2H), 8.02 - 7.85 (m, 1H), 7.77 (s, 1H), 7.59 - 7.47 (m, 3H), 7.32 (d, J = 8.7 Hz, 1H), 4.46 - 4.36 (m, 2H), 4.23 - 4.18 (m, 1H), 4.02 - 3.97 (m, 1H), 3.94 - 3.90 (m, 4H), 3.67 - 3.63 (m, 3H), 3.41 (d, J = 6.8 Hz, 3H), 3.27 - 3.05 (m, 9H), 2.93 (t, J = 7.0 Hz, 2H), 2.78 (t, J = 11.1 Hz, 1H), 2.69 - 2.53 (m, 2H), 2.23 - 2.03 (m, 2H), 1.98 - 1.73 (m, 8H), 1.62 - 1.41 (m, 6H), 0.76 (t, J = 7.4 Hz, 3H).

Example 80. Synthesis of N- [1-[3-[4-[3-(2,4-dioxohexahydropyrimidin-1-yl)-1-methyl-indazol-6-yl]piperazin-1-yl]propanoyl]-4-piperidyl]-3-methoxy-4-[[rac-(7R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-7H-pteridin-2-yl]amino]benzamide (Compound 80)

Step 1. Synthesis of 3-[(6-bromo-1-methyl-indazol-3-yl)amino]propanoic acid (2)

Acrylic acid (1.05 g, 14.60 mmol) was added to a solution of 6-bromo-1-methyl-indazol-3-amine (3.00 g, 13.27 mmol) in AcOH (1.8 mL) and H ₂ O (3 mL). The mixture was stirred at 100 °C for 16 h. LCMS showed ~50% The target compound was identified. The mixture was adjusted to pH=10 with NaOH (2 N), washed with EtOAc (30 mL x 3), and the organic phase was removed. The aqueous phase was adjusted to pH=5 with HCl (2 M), and extracted with EtOAc (50 mL x 3). The combined organic layers were washed with brine (30 mL x 2), dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure to obtain the title compound (2.1 g, 6.90 mmol, 52.02% yield, 98% purity) as a pale red solid. MS(M+H) ⁺ =298.1.

¹ H NMR (400 MHz, DMSO- d ₆ ) δ = 12.36 - 11.93 (m, 1H), 7.65 - 7.60 (m, 2H), 7.01 (dd, J = 8.4, 1.6 Hz, 1H), 6.33 - 6.16 (m, 1H), 3.74 (s, 3H), 3.47 - 3.41 (m, 2H), 2.59 (t, J = 6.8 Hz, 2H).

Step 2. Synthesis of 1-(6-bromo-1-methyl-indazol-3-yl)hexahydropyrimidine-2,4-dione (3)

To a solution of 3-[(6-bromo-1-methyl-indazol-3-yl)amino]propanoic acid (2.10 g, 6.90 mmol) in AcOH (21 mL) was added NaOCN (673 mg, 10.35 mmol). The mixture was stirred at 100 °C for 16 h. Then, HCl (2 M, 21 mL) was added, and the mixture was stirred at 60 °C for 3 h. By LCMS ~60% of The target compound was identified. After cooling the mixture to room temperature, it was filtered, and the filter cake was vacuum-dried to obtain the title compound (710 mg, 2.20 mmol, 31.83% yield) as a pale yellow solid. MS(M+H) ⁺ = 323.0.

¹ H NMR (400 MHz, DMSO- d ₆ ) δ = 10.60 (s, 1H), 8.04 -7.90 (m, 1H), 7.62 (d, J = 8.8 Hz, 1H), 7.24 (dd, J = 8.8, 1.6 Hz, 1H), 3.98 (s, 3H), 3.93 (t, J = 6.8 Hz, 2H), 2.76 (t, J = 6.8 Hz, 2H).

Step 3. Synthesis of tert-butyl 4-[3-(2,4-dioxohexahydropyrimidin-1-yl)-1-methyl-indazol-6-yl]piperazine-1-carboxylate (5)

To a solution of 1-(6-bromo-1-methyl-indazol-3-yl)hexahydropyrimidine-2,4-dione (660 mg, 2.04 mmol) and tert-butyl piperazine-1-carboxylate (1.14 g, 6.13 mmol) in dioxane (50 mL) were added Pd-PEPPSI-IHeptCl (198.7 mg, 204.24 μmol) and Cs ₂ CO ₃ (1.33 g, 4.08 mmol). The mixture was stirred at 100 °C under CN ₂ for 16 h. The target compound was confirmed to be ~78% by LCMS. The mixture was cooled to room temperature, diluted with THF (150 mL), and filtered. The filtrate was concentrated under reduced pressure. The residue was triturated with MTBE (20 mL) at 25 °C for 10 min to give the title compound as a brown solid (420 mg, 921.39 μmol, 45.11% yield, 94% purity). MS(M+H) ⁺ =429.3.

Step 4. Synthesis of 1-(1-methyl-6-piperazin-1-yl-indazol-3-yl)hexahydropyrimidine-2,4-dione (6)

The title compound (407 mg, 920.00 μmol, 99.85% yield, TFA) was obtained as a brown oil by a similar method to step 2 of Example 32. MS(M+H) ⁺ = 329.1.

Step 5. Synthesis of tert-butyl N-[1-[3-[4-[3-(2,4-dioxohexahydropyrimidin-1-yl)-1-methyl-indazol-6-yl]piperazin-1-yl]propanoyl]-4-piperidyl]carbamate (8)

The title compound (160 mg, 252.62 μmol, 27.46% yield, 92% purity) was obtained as a pale yellow solid by a similar method to step 4 of Example 79. MS(M+H) ⁺ =583.4.

Step 6. Synthesis of 1-[6-[4-[3-(4-amino-1-piperidyl)-3-oxo-propyl]piperazin-1-yl]-1-methyl-indazol-3-yl]hexahydropyrimidine-2,4-dione (9)

The title compound (141 mg, 236.67 μmol, 99.93% yield, TFA) was obtained as a brown oil by a similar method to step 2 of Example 32. MS(M+H) ⁺ = 483.3.

Step 7. Synthesis of N -[1-[3-[4-[3-(2,4-dioxohexahydropyrimidin-1-yl)-1-methyl-indazol-6-yl]piperazin-1-yl]propanoyl]-4-piperidyl]-3-methoxy-4-[[rac-(7R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-7H-pteridin-2-yl]amino]benzamide (Compound 80)

The title compound (82.9 mg, 91.84 μmol, 38.80% yield, 98.6% purity) was obtained as a white-yellow solid by a similar method to step 6 of Example 79. MS(M+H) ⁺ =890.5.

¹ H NMR (400 MHz, DMSO- d ₆ ) δ = 10.50 (s, 1H), 8.42 (d, J = 9.2 Hz, 1H), 8.11 (d, J = 8.0 Hz, 1H), 7.85 (s, 1H), 7.60 (s, 1H), 7.52 - 7.43 (m, 3H), 6.95 - 6.89 (m, 1H), 6.85 - 6.78 (m, 1H), 4.45 - 4.30 (m, 2H), 4.27 - 4.21 (m, 1H), 4.13 - 3.95 (m, 2H), 3.94 (s, 3H), 3.91 - 3.86 (m, 5H), 3.26 - 3.21 (m, 7H), 3.18 - 3.11 (m, 1H), 2.73 (t, J = 6.8 Hz, 2H), 2.64 - 2.54 (m, 8H), 2.49 - 2.40 (m, 1H), 2.05 - 1.96 (m, 1H), 1.95 - 1.85 (m, 3H), 1.88 - 1.73 (m, 5H), 1.69 - 1.57 (m, 3H), 1.54 - 1.35 (m, 2H), 0.76 (t, J = 7.2 Hz, 3H).

Example 81. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(1-(2-(1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)ethyl)piperidin-4-yl)-3-methoxybenzamide (Compound 81)

Step 1. Synthesis of tert-butyl (R)-4-(4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzamido)piperidine-1-carboxylate (3)

To a solution of (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoic acid (0.5 g, 1.22 mmol) in DMF (8 mL) was added HATU (508.26 mg, 1.34 mmol) and DIPEA (471.17 mg, 3.65 mmol, 635.00 μL) at 20 °C. The mixture was stirred for 10 min. Then, tert-butyl 4-aminopiperidine-1-carboxylate (267.72 mg, 1.34 mmol) was added at 20 °C, and the resulting mixture was stirred at 20 °C for 1 h. LCMS confirmed complete consumption of the starting material and the peak of the target mass (76%). The reaction mixture was diluted with H ₂ O (30 mL) and extracted with EtOAc (20 mL x 3). The organic layer was washed with brine (20 mL x 3), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (10 g SepaFlash® silica flash column, eluent of 30–100% EtOAc/Petroleum ether to 10–10% MeOH/DCM gradient @ 200 mL/min) to obtain the title compound (670 mg, 1.13 mmol, 92.86% yield) as a yellow solid. MS(M+H) ⁺ = 594.4

Step 2. Synthesis of (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxy-N-(piperidin-4-yl)benzamide (4)

To a solution of tert-butyl (R)-4-(4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzamido)piperidine-1-carboxylate (670 mg, 1.13 mmol) in DCM (8 mL) was added HCl/dioxane (2 M, 16 mL) at 20 °C, and the resulting mixture was stirred at 20 °C for 12 h. The peak of the target mass (95%) was confirmed by LCMS. The reaction mixture was concentrated under reduced pressure to obtain the title compound (0.6 g, crude, HCl salt) as a white solid. MS(M+H) ⁺ = 494.4

Step 3. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(1-(2-(1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)ethyl)piperidin-4-yl)-3-methoxybenzamide (Compound 81)

The title compound (154.4 mg, 169.61 μmol, 26.66% yield, 87% purity) was obtained as a white solid by a similar method to step 1 of Example 59. MS(M+H) ⁺ = 792.6

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.76 (s, 1H), 8.42 (d, J = 8.9 Hz, 1H), 8.06 (br d, J = 7.4 Hz, 1H), 7.89 (s, 1H), 7.62 (s, 1H), 7.53 - 7.43 (m, 2H), 7.03 (d, J = 8.6 Hz, 2H), 6.88 (d, J = 8.6 Hz, 2H), 4.48 - 4.37 (m, 1H), 4.36 - 4.27 (m, 1H), 3.94 (s, 3H), 3.83 - 3.75 (m, 1H), 3.71 (br dd, J = 4.9, 10.8 Hz, 1H), 3.68 - 3.57 (m, 2H), 3.23 (s, 3H), 3.00 - 2.79 (m, 2H), 2.67 - 2.59 (m, 2H), 2.48 - 2.42 (m, 1H), 2.33 (br d, J = 1.5 Hz, 1H), 2.18 - 2.06 (m, 1H), 2.05 - 1.98 (m, 2H), 1.97 - 1.91 (m, 2H), 1.85 - 1.71 (m, 8H), 1.65 - 1.52 (m, 4H), 1.41 (br s, 3H), 1.31 - 1.12 (m, 7H), 0.88 - 0.69 (m, 1H)

Example 82. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(2-(1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)ethyl)piperazin-1-yl)-3-methoxybenzamide (Compound 82)

Step 1. Synthesis of 2-(1-(4-bromophenyl)piperidin-4-yl)ethan-1-ol (3)

To a solution of 1-bromo-4-iodobenzene (12 g, 42.42 mmol) and 2-(piperidin-4-yl)ethan-1-ol (5.48 g, 42.42 mmol) in DMSO (200 mL) were added CuI (1.62 g, 8.51 mmol), K ₂ CO ₃ (11.72 g, 84.83 mmol) and L-proline (1.96 g, 16.99 mmol) at 20 °C under CN ₂ , and the resulting mixture was stirred at 100 °C for 12 h. LCMS confirmed complete consumption of the starting material and the peak of the target mass (37%). The reaction mixture was diluted with H ₂ O (600 mL) and extracted with EtOAc (300 mL x 3). The organic layer was washed with brine (300 mL x 3), dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (100 g SepaFlash® silica flash column, Eluent of 12–60% EtOAc/Petroleum ether gradient @ 200 mL/min) to give the title compound (6.8 g, 23.93 mmol, 56.41% yield) as a white solid. MS(M+H) ⁺ = 284.1 & 286.1

Step 2. Synthesis of 2-(1-(4-(2,6-bis(benzyloxy)pyridin-3-yl)phenyl)piperidin-4-yl)ethan-1-ol (5)

To a solution of _2- (1-(4-bromophenyl)piperidin-4-yl)ethan-1-ol (6.8 g, 23.93 mmol) and (2,6-bis(benzyloxy)pyridin-3-yl)boronic acid (10.98 g, 26.32 mmol) in dioxane (100 mL) and H 2 O (20 mL) were added Pd(dppf)Cl ₂ (1.75 g, 2.39 mmol) and K ₂ CO ₃ (9.92 g, 71.78 mmol) under 20 °C CN ₂ , and the resulting mixture was stirred at 90 °C for 12 h. LCMS confirmed complete consumption of the starting material and the peak of the target mass (44%). The reaction mixture was diluted with H ₂ O (300 mL) and extracted with EtOAc (200 mL x 3). The organic layer was dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (100 g SepaFlash® silica flash column, eluent of 12–60% EtOAc/Petroleum ether gradient @ 200 mL/min) to give the title compound (7.8 g, 15.77 mmol, 65.91% yield) as a white solid. MS (M+H) ⁺ = 495.2

Step 3. Synthesis of 3-(4-(4-(2-hydroxyethyl)piperidin-1-yl)phenyl)piperidine-2,6-dione (6)

To a suspension of Pd/C (3 g, 10% purity) in EtOH (40 mL), EtOAc (40 mL), and DCM (8 mL) was added 2-(1-(4-(2,6-bis(benzyloxy)pyridin-3-yl)phenyl)piperidin-4-yl)ethan-1-ol (7.8 g, 15.77 mmol) under N ₂ . The suspension was degassed and purged three times with H ₂ . The mixture was stirred at 20 °C under CH ₂ (45 Psi) for 16 h. LCMS confirmed complete consumption of the starting material and a peak of the target mass (87%). The reaction mixture was filtered, the filter cake was washed with MeOH (500 mL), and the filtrate was concentrated under reduced pressure to give the title compound (3.2 g, 10.11 mmol, 64.14% yield) as a white solid. MS(M+H) ⁺ =317.3

Step 4. Synthesis of 2-(1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)acetaldehyde (7)

The title compound (0.5 g, crude) as a yellow oil was obtained by synthesis in a similar manner to step 2 of Example 56.

Step 5. Synthesis of tert-butyl (4-(2-(1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)ethyl)piperazin-1-yl)carbamate (8)

To a solution of 2-(1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)acetaldehyde (0.3 g, 954.27 μmol) and tert-butyl piperazin-1-ylcarbamate (288.09 mg, 1.43 mmol) in DCM (8 mL) were added AcOH (114.61 mg, 1.91 mmol, 109.26 μL) and MgSO ₄ (172.29 mg, 1.43 mmol) at 20 °C. The mixture was stirred for 12 h. Then, NaBH(OAc) ₃ (606.74 mg, 2.86 mmol) was added at 20 °C, and the resulting mixture was stirred at 20 °C for 12 h. LCMS confirmed complete consumption of the starting material and the peak of the target mass (51%). The reaction mixture was diluted with H ₂ O (30 mL) and extracted with DCM (30 mL x 3). The organic layer was washed with saturated NaHCO ₃ (30 mL x 3), dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (10 g SepaFlash® silica flash column, Eluent of 33–100% EtOAc/Petroleum ether to gradient @ 200 mL/min) to give the title compound (87 mg, 174.12 μmol, 18.25% yield) as a yellow solid. MS(M+H) ⁺ = 500.5

Step 6. Synthesis of 3-(4-(4-(2-(4-aminopiperazin-1-yl)ethyl)piperidin-1-yl)phenyl)piperidine-2,6-dione (9)

To a solution of tert-butyl (4-(2-(1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)ethyl)piperazin-1-yl)carbamate (87 mg, 174.12 μmol) in DCM (6 mL) was added TFA (155.21 μL) at 20 °C, and the resulting mixture was stirred at 20 °C for 12 h. LCMS confirmed complete consumption of the starting material and the peak of the target mass (58%). The reaction mixture was concentrated under reduced pressure to obtain the title compound (90 mg, crude, TFA salt) as a yellow oil. MS(M+H) ⁺ = 400.3

Step 7. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(2-(1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)ethyl)piperazin-1-yl)-3-methoxybenzamide (Compound 82)

To a solution of (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoic acid (72.11 mg, 175.25 μmol) in DMF (3 mL) were added HATU (79.96 mg, 210.30 μmol) and DIPEA (226.50 mg, 1.75 mmol, 305.25 μL) at 20 °C. The mixture was stirred for 10 min. Afterwards, 3-(4-(4-(2-(4-aminopiperazin-1-yl)ethyl)piperidin-1-yl)phenyl)piperidine-2,6-dione (90 mg, 175.25 μmol, TFA salt) was added at 20 °C, and the resulting mixture was stirred at 20 °C for 13 h. Complete consumption of the starting material and the peak of the target mass (32%) were confirmed by LCMS. The reaction mixture was diluted with H ₂ O (15 mL), and then extracted with EtOAc (10 mL x 3). The organic layer was dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure. The residue was purified by prep-HPLC (column: Phenomenex Luna C18 150*25 mm*10um; mobile phase: [H ₂ O (0.1% TFA) - ACN]; gradient: 0% - 25% B over 15.0 min). The eluate was adjusted to pH=8 with saturated NaHCO ₃ and extracted with DCM (20 mL x 2). The organic layer was dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure. The product was dissolved in a mixed solution (20 mL, ACN: H ₂ O = 1:1) and lyophilized to obtain the title compound (24.9 mg, 28.89 μmol, 16.48% yield, 92% purity) as a white solid. MS(M+H) ⁺ = 793.6

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.74 (br s, 1H), 9.31 - 9.21 (m, 1H), 8.46 - 8.36 (m, 1H), 7.89 (s, 1H), 7.62 (s, 1H), 7.46 - 7.36 (m, 2H), 7.03 (br d, J = 8.6 Hz, 2H), 6.88 (br d, J = 8.8 Hz, 2H), 4.48 - 4.36 (m, 1H), 4.35 - 4.28 (m, 1H), 3.93 (s, 3H), 3.71 (dd, J = 5.0, 10.9 Hz, 1H), 3.68 - 3.58 (m, 2H), 3.23 (s, 3H), 2.92 (br s, 4H), 2.60 (br dd, J = 8.3, 10.6 Hz, 2H), 2.44 - 2.39 (m, 1H), 2.37 - 2.33 (m, 2H), 2.15 - 2.08 (m, 1H), 2.04 - 1.97 (m, 2H), 1.92 (br d, J = 7.5 Hz, 1H), 1.85 - 1.74 (m, 6H), 1.63 - 1.57 (m, 2H), 1.41 - 1.37 (m, 2H), 1.24 (br s, 3H), 1.22 - 1.17 (m, 6H), 0.86 - 0.83 (m, 1H), 0.78 - 0.75 (m, 1H).

Example 83. Synthesis of 4-(((R)-7,8-diethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(7-(2-(1-(4-((2,6-dioxopiperidin-3-yl)amino)-2-fluorophenyl)piperidin-4-yl)ethyl)-7-azaspiro[3.5]nonan-2-yl)-3-methoxybenzamide (Compound 83)

Step 1. Synthesis of 2-(1-(2-fluoro-4-nitrophenyl)piperidin-4-yl)ethan-1-ol (3)

To a solution of 1,2-difluoro-4-nitrobenzene (3 g, 18.86 mmol, 2.09 mL) and 2-(piperidin-4-yl)ethan-1-ol (2.44 g, 18.86 mmol) in DMF (50 mL) was added K ₂ CO ₃ (5.21 g, 37.71 mmol), and the mixture was stirred at 15 °C for 14 h. The desired mass peak (94%) was identified by LCMS. The mixture was diluted with EtOAc (50 mL) and brine (100 mL), and extracted with EtOAc (30 mL x 2). The combined organic layer was washed with brine (30 mL x 2), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (12 g SepaFlash® silica flash column, Eluent of 60–100% EtOAc/Petroleum ether gradient @ 100 mL/min) to give the title compound (5.1 g, 16.54 mmol, 87.70% yield, 87% purity) as a yellow solid. MS(M+H) ⁺ = 269.2.

Step 2. Synthesis of 2-(1-(2-fluoro-4-nitrophenyl)piperidin-4-yl)ethyl 4-methylbenzenesulfonate (4)

To a solution of 2-(1-(2-fluoro-4-nitrophenyl)piperidin-4-yl)ethan-1-ol (2.5 g, 8.11 mmol) in DCM (50 mL) were added TEA (2.46 g, 24.32 mmol, 3.39 mL), DMAP (99.04 mg, 810.71 μmol), and TosCl (2.32 g, 12.16 mmol), and the mixture was stirred at 15 °C for 14 h. The desired mass peak (85%) was identified by LCMS. The mixture was diluted with water (30 mL) and extracted with EtOAc (20 mL). The combined organic layer was washed with water (30 mL), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (20 g SepaFlash® silica flash column, eluent of 60–100% EtOAc/Petroleum ether gradient @ 100 mL/min) to give the title compound (3.1 g, 7.34 mmol, 90.51% yield) as a yellow solid. MS(M+H) ⁺ = 423.2

Step 3. Synthesis of benzyl (7-(2-(1-(2-fluoro-4-nitrophenyl)piperidin-4-yl)ethyl)-7-azaspiro[3.5]nonan-2-yl)carbamate (6)

To a solution of benzyl (7-azaspiro[3.5]nonan-2-yl)carbamate (0.8 g, 2.06 mmol, TFA salt) in DMF (10 mL) were added K ₂ CO ₃ (1.42 g, 10.30 mmol), NaI (155 mg, 1.03 mmol), and 2-(1-(2-fluoro-4-nitrophenyl)piperidin-4-yl)ethyl 4-methylbenzenesulfonate (1.2 g, 2.84 mmol), and the mixture was stirred at 60 °C for 14 h. The desired mass peak was identified by LCMS. The mixture was diluted with water (50 mL) and extracted with EtOAc (10 mL). The organic layer was washed with water (30 mL), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (12 g SepaFlash® silica flash column, Eluent of 0–10% MeOH/EtOAc gradient @ 100 mL/min) to give the title compound (0.9 g, 1.72 mmol, 83.28% yield, 100% purity) as a yellow oil. MS(M+H) ⁺ = 525.2.

Step 4. Synthesis of benzyl (7-(2-(1-(4-amino-2-fluorophenyl)piperidin-4-yl)ethyl)-7-azaspiro[3.5]nonan-2-yl)carbamate (7)

To a solution of benzyl (7-(2-(1-(2-fluoro-4-nitrophenyl)piperidin-4-yl)ethyl)-7-azaspiro[3.5]nonan-2-yl)carbamate ( _0.9 g, 1.72 mmol) and NH ₄ Cl (275.29 mg, 5.15 mmol) in EtOH (15 mL) and H 2 O (5 mL) was added Fe (287.41 mg, 5.15 mmol), and the mixture was stirred at 80 °C for 3.5 h. The desired mass peak (100%) was confirmed by LCMS. The mixture (80 °C) was filtered, and the filter cake was washed with MeOH (50 mL) and EtOAc (50 mL). The filtrate was concentrated under reduced pressure. The product was diluted with EtOAc (20 mL) and water (20 mL), adjusted to pH= ₈ with saturated _Na2CO3 , and extracted with EtOAc (10 mL). The organic layer was washed with water (20 mL), dried _{over Na2SO4} , and filtered. The filtrate was concentrated under reduced pressure to obtain the title compound (860 mg, crude) as a yellow oil. MS(M+H) ⁺ =495.4.

Step 5. Synthesis of benzyl (7-(2-(1-(4-((2,6-dioxopiperidin-3-yl)amino)-2-fluorophenyl)piperidin-4-yl)ethyl)-7-azaspiro[3.5]nonan-2-yl)carbamate (9)

A solution of benzyl (7-(2-(1-(4-amino-2-fluorophenyl)piperidin-4-yl)ethyl)-7-azaspiro[3.5]nonan-2-yl)carbamate (860 mg, 1.74 mmol), 3-bromopiperidine-2,6-dione (834 mg, 4.34 mmol), NaHCO ₃ (585 mg, 6.96 mmol, 270.96 μL), and TBAI (129 mg, 349.25 μmol) in ACN (5 mL) was stirred at 80 °C for 60 h. LCMS confirmed that the starting material remained. The reaction mixture was then stirred at 85 °C for an additional 14 h. LCMS confirmed that the starting material remained and a peak of the desired mass was present. The mixture was diluted with EtOAc (50 mL) and water (30 mL), and the suspension was stirred at 15 °C for 1 h. The suspension was filtered, and the filter cake was washed with EtOAc (30 mL). The filter cake was collected to give product A. The filtrate was extracted with EtOAc (10 mL x 3), and the combined organic layers were dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure to give product B, which was combined with product A, and purified by flash silica gel chromatography (12 g SepaFlash® silica flash column, Eluent of 0–10% MeOH/EtOAc gradient @ 100 mL/min) to give two batches of product. Batch 1: Benzyl (7-(2-(1-(4-((2,6-dioxopiperidin-3-yl)amino)-2-fluorophenyl)piperidin-4-yl)ethyl)-7-azaspiro[3.5]nonan-2-yl)carbamate (280 mg, 462.24 μmol, 26.59% yield) as a blue oil and Batch 1: Benzyl (7-(2-(1-(4-((2,6-dioxopiperidin-3-yl)amino)-2-fluorophenyl)piperidin-4-yl)ethyl)-7-azaspiro[3.5]nonan-2-yl)carbamate (170 mg, 280.65 μmol, 16.14% yield) as a gray oil. MS(M+H) ⁺ = 606.6

Step 6. Synthesis of 3-((4-(4-(2-(2-amino-7-azaspiro[3.5]nonan-7-yl)ethyl)piperidin-1-yl)-3-fluorophenyl)amino)piperidine-2,6-dione (10)

A solution of benzyl (7-(2-(1-(4-((2,6-dioxopiperidin-3-yl)amino)-2-fluorophenyl)piperidin-4-yl)ethyl)-7-azaspiro[3.5]nonan-2-yl)carbamate (280 mg, 462.24 μmol) in TFA (15.35 g, 134.62 mmol, 10 mL) was stirred at 40 °C for 3 h. The desired mass peak (47%) was identified by LCMS. The mixture was concentrated under reduced pressure. After combining the product with another batch (170 mg scale), the product was purified by prep-HPLC (column: Phenomenex luna C18 150*40 mm* 15um; mobile phase: [water (TFA) -ACN]; gradient: 0%-15% B over 12 min), and the eluate was lyophilized to obtain the title compound (0.2 g, 334.68 μmol, 72.40% yield, 98% purity, TFA salt) as a yellow solid. MS(M+H) ⁺ =472.3.

Step 7. Synthesis of 4-(((R)-7,8-diethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(7-(2-(1-(4-((2,6-dioxopiperidin-3-yl)amino)-2-fluorophenyl)piperidin-4-yl)ethyl)-7-azaspiro[3.5]nonan-2-yl)-3-methoxybenzamide (Compound 83)

To a solution of (R)-4-((7,8-diethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoic acid (0.13 g, 337.30 μmol) and HATU (153.90 mg, 404.76 μmol) in DMF (1 mL) was added DIPEA (148.40 mg, 1.15 mmol, 0.2 mL), and the mixture was stirred at 15 °C for 30 min. A solution of 3-((4-(4-(2-(2-amino-7-azaspiro[3.5]nonan-7-yl)ethyl)piperidin-1-yl)-3-fluorophenyl)amino)piperidine-2,6-dione (0.2 g, 341.51 μmol, TFA salt) in DMF (1 mL) was added, and the mixture was stirred at 15 °C for an additional 1 h. The desired mass peak (52%) was identified by LCMS. The mixture was diluted with EtOAc (10 mL) and saturated NaHCO ₃ (10 mL), and extracted with EtOAc (10 mL x 3). The combined organic layer was washed with brine (10 mL) and saturated NaHCO ₃ (10 mL), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure. The product was purified by prep-HPLC (column: Phenomenex luna C18 150*40 mm* 15um; mobile phase: [water (TFA) -ACN]; gradient: 9%-39% B over 12 min) and the eluate was lyophilized to give the title compound as a gray solid. (162.32 mg, 133.31 μmol, 39.52% yield, 97% purity, 3TFA salt) was obtained. MS(M+H) ⁺ =839.2.

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.81 (s, 1H), 9.44 - 9.12 (m, 2H), 8.62 (br d, J = 4.5 Hz, 1H), 8.13 (br d, J = 8.2 Hz, 1H), 7.81 (s, 1H), 7.60 - 7.50 (m, 2H), 7.14 - 6.90 (m, 1H), 6.62 - 6.42 (m, 2H), 4.55 (br t, J = 4.2 Hz, 1H), 4.43 (br dd, J = 7.9, 16.0 Hz, 1H), 4.33 - 4.27 (m, 1H), 3.94 (s, 3H), 3.92 - 3.84 (m, 1H), 3.48 - 3.35 (m, 3H), 3.30 - 3.19 (m, 5H), 3.14 - 3.05 (m, 2H), 2.99 - 2.86 (m, 3H), 2.77 - 2.65 (m, 1H), 2.61 - 2.53 (m, 1H), 2.40 - 2.33 (m, 1H), 2.20 - 2.11 (m, 1H), 2.09 - 2.03 (m, 1H), 2.02 - 1.83 (m, 6H), 1.82 - 1.59 (m, 8H), 1.51 - 1.34 (m, 3H), 1.24 (t, J = 7.1 Hz, 3H), 0.74 (t, J = 7.4 Hz, 3H).

Examples 84 & 85. 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(((1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)methyl)amino)piperidin-1-yl)-3-methoxybenzamide (Compound 84) and Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(((1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)methyl)(methyl)amino)piperidin-1-yl)-3-methoxybenzamide (Compound 85)

Step 1. Synthesis of 3-(4-(4-(((2,4-dimethoxybenzyl)amino)methyl)piperidin-1-yl)phenyl)piperidine-2,6-dione (2)

To a solution of 1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidine-4-carbaldehyde (400 mg, 1.33 mmol) and (2, 4-dimethoxyphenyl)methanamine (445.36 mg, 2.66 mmol, 400.14 μL) in MeOH (10 mL) was added AcOH (239.93 mg, 4.00 mmol, 228.72 μL), and the mixture was stirred at 20 °C for 1 h. NaBH ₃ CN (167.38 mg, 2.66 mmol) was added, and the mixture was stirred at 20 °C for 16 h. The peak of the target mass (35%) was confirmed by LCMS. The mixture was filtered, and the filtrate was purified by prep-HPLC (column: Phenomenex Luna C18 150*25 mm*10 um; mobile phase: [H ₂ O (0.1% TFA)-ACN]; gradient: 3%-33% B over 13.0 min), and the eluate was lyophilized to obtain the title compound (340 mg, 752.95 μmol, 56.54% yield) as a yellow oil. MS(M+H) ⁺ =452.3

Step 2. Synthesis of 3-(4-(4-(aminomethyl)piperidin-1-yl)phenyl)piperidine-2,6-dione (3)

A mixture of 3-(4-(4-(((2,4-dimethoxybenzyl)amino)methyl)piperidin-1-yl)phenyl)piperidine-2,6-dione (340 mg, 752.95 μmol) in TFA (5 mL) was stirred at 80 °C for 16 h. The peak of the target mass (30%) was identified by LCMS. The mixture was concentrated under reduced pressure, and the residue was purified by prep-HPLC (column: Phenomenex Luna C18 150*25 mm*10 μm; mobile phase: [H ₂ O (0.1% TFA) -ACN]; gradient: 3%-33% B over 13.0 min) to give the title compound (0.12 g, 398.17 μmol, 52.88% yield) as a yellow oil. MS(M+H) ⁺ =302.3

Step 3. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(((1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)methyl)amino)piperidin-1-yl)-3-methoxybenzamide (Compound 84)

The title compound (81 mg, 91.93 μmol, 38.19% yield, 90% purity) was obtained as a white solid by a similar method to step 5 of Example 30. MS(M+H) ⁺ = 793.6

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.77 (s, 1H), 9.25 (s, 1H), 8.46 - 8.37 (m, 1H), 7.90 (s, 1H), 7.63 (s, 1H), 7.47 - 7.38 (m, 2H), 7.03 (d, J = 8.8 Hz, 2H), 6.89 (d, J = 8.8 Hz, 2H), 4.48 - 4.38 (m, 1H), 4.32 (q, J = 6.7 Hz, 1H), 3.94 (s, 3H), 3.76 - 3.63 (m, 3H), 3.24 (s, 3H), 3.00 (d, J = 10.6 Hz, 2H), 2.79 (t, J = 9.7 Hz, 2H), 2.69 - 2.59 (m, 3H), 2.48 - 2.43 (m, 3H), 2.20 - 2.09 (m, 1H), 2.06 - 1.97 (m, 2H), 1.95 - 1.91 (m, 1H), 1.89 - 1.75 (m, 8H), 1.67 - 1.59 (m, 2H), 1.52 - 1.37 (m, 3H), 1.31 - 1.16 (m, 7H).

Step 4. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(((1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)methyl)(methyl)amino)piperidin-1-yl)-3-methoxybenzamide (Compound 85)

To a solution of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(((1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)methyl)amino)piperidin-1-yl)-3-methoxybenzamide (60 mg, 75.67 μmol) and HCHO (18.42 mg, 227.00 μmol, 16.90 μL) in DCM (4 mL) and DMF (1 mL) was added AcOH (6.82 mg, 113.50 μmol, 6.50 μL) at 20 °C. After stirring for 1 h, NaBH(OAc) ₃ (48.11 mg, 227.00 μmol) was added at 20 °C, and the resulting mixture was stirred at 20 °C for 12 h. LCMS confirmed complete consumption of the starting material and the peak of the target mass (87%). The reaction mixture was diluted with H ₂ O (20 mL) and extracted with DCM (20 mL x 3). The organic layer was washed with saturated NaHCO ₃ (20 mL x 3), dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure. The residue was purified by prep-HPLC (column: Phenomenex Luna C18 150*25 mm*10 μm; mobile phase: [H ₂ O (0.1% TFA) -ACN]; gradient: 0%-25% B over 15.0 min) to obtain the eluate. The pH was adjusted to 8 by adding saturated NaHCO ₃ and extracted with DCM (20 mL x 2). The organic layer was dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure to obtain the product. The product was dissolved in a mixed solvent (20 mL, ACN: H ₂ O = 1:1) and lyophilized to obtain the title compound (21.6 mg, 25.43 μmol, 33.61% yield, 95% purity) as a white solid. MS(M+H) ⁺ = 807.4

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.86 - 10.60 (m, 1H), 9.31 - 9.14 (m, 1H), 8.42 (d, J = 8.7 Hz, 1H), 7.89 (s, 1H), 7.62 (s, 1H), 7.45 - 7.34 (m, 2H), 7.03 (d, J = 8.2 Hz, 2H), 6.88 (d, J = 8.4 Hz, 2H), 4.47 - 4.36 (m, 1H), 4.32 (q, J = 6.6 Hz, 1H), 3.93 (s, 3H), 3.75 - 3.60 (m, 3H), 3.23 (s, 3H), 3.03 (d, J = 9.0 Hz, 2H), 2.78 (t, J = 10.9 Hz, 2H), 2.62 (t, J = 11.4 Hz, 3H), 2.44 (d, J = 4.8 Hz, 1H), 2.37 - 2.28 (m, 1H), 2.27 - 2.23 (m, 2H), 2.20 (s, 3H), 2.15 - 2.06 (m, 1H), 2.05 - 1.97 (m, 2H), 1.95 - 1.87 (m, 1H), 1.80 - 1.73 (m, 4H), 1.73 - 1.68 (m, 2H), 1.61 - 1.52 (m, 4H), 1.25 - 1.20 (m, 3H), 1.18 (d, J = 9.3 Hz, 3H), 0.88 - 0.72 (m, 2H)

Example 86. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(((1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)amino)methyl)piperidin-1-yl)-3-methoxybenzamide (Compound 86)

Step 1. Synthesis of tert-butyl (4-formylpiperidin-1-yl)carbamate (2)

To a solution of tert-butyl (4-(hydroxymethyl)piperidin-1-yl)carbamate (2 g, 8.68 mmol) in DCM (20 mL) and DMSO (10 mL) were added TEA (3.64 g, 35.92 mmol, 5 mL) and SO ₃ . Py (2.8 g, 17.59 mmol). The mixture was stirred at 20 °C for 2 h. The peak of the target mass was identified by LCMS, and a new spot (Rf = 0.28) was confirmed by TLC (Petroleum ether:EtOAc = 1:2). H ₂ O (15 mL) was added to the reaction mixture, diluted with DCM (20 mL), and NaHCO ₃ (sat. aq, 10 mL) was added to adjust the pH to 9. The mixture was extracted with DCM (20 mL × 2), the mixed organic layer was washed with brine (30 mL × 3), dried over Na ₂ SO ₄ , filtered, and the filtrate was concentrated under reduced pressure to obtain the title compound (1.8 g, crude) as a yellow oil. MS (M + H - 56) ⁺ = 173.1.

Step 2. Synthesis of tert-butyl (4-(((1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)amino)methyl)piperidin-1-yl)carbamate (4)

To a solution of 3-(4-(4-aminopiperidin-1-yl)phenyl)piperidine-2,6-dione (200 mg, 617.63 μmol HCl) in DCM (6 mL) and DMF (2 mL) were added tert-Butyl (4-formylpiperidin-1-yl)carbamate (200 mg, 876.09 μmol) and TEA (374.99 mg, 3.71 mmol, 515.80 μL). The mixture was stirred at 20 °C for 1 h. Then, NaBH(OAc) ₃ (800 mg, 3.77 mmol) was added to the mixture at 0 °C, and the mixture was stirred at 20 °C for 15 h. The peak of the target mass (52%) was confirmed by LCMS. H ₂ O (15 mL) was added to the reaction mixture, diluted with DCM (30 mL), and adjusted to pH = 9 by adding NaHCO ₃ (sat. aq, 40 mL). The mixture was extracted with DCM (50 mL × 2), and the combined organic layer was washed with brine (50 mL × 2), dried over Na ₂ SO ₄ , filtered, and the filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (12 g SepaFlash® silica flash column, eluent of 5–20% EtOH:DCM 120 mL/min) to give the title compound (130 mg, 260.19 μmol, 42.13% yield) as a yellow solid. MS (M+H) ⁺ = 500.4

Step 3. Synthesis of 3-(4-(4-(((1-aminopiperidin-4-yl)methyl)amino)piperidin-1-yl)phenyl)piperidine-2,6-dione (5)

To a solution of tert-butyl (4-(((1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)amino)methyl)piperidin-1-yl)carbamate (100 mg, 200.14 μmol) in DCM (3 mL) was added TFA (4.61 g, 40.39 mmol, 3 mL) at 0 °C. The mixture was stirred at 20 °C under CN ₂ for 2 h. The major peak of the desired mass was identified by LCMS. The reaction mixture was concentrated under reduced pressure to obtain the title compound (92 mg, crude, TFA) as a yellow oil. MS(M+H) ⁺ = 400.3

Step 4. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(((1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)amino)methyl)piperidin-1-yl)-3-methoxybenzamide (Compound 86)

The title compound (1.9 mg, 2.11 μmol, 1.16% yield, 88% purity) was obtained as a white solid by a similar method to step 3 of Example 59. MS (M+H) ⁺ = 793.5

¹ H NMR (400 MHz, DMSO- d ₆ ) δ = 10.78 (s, 1H), 9.28 - 9.20 (m, 1H), 8.45 - 8.40 (m, 1H), 7.94 - 7.88 (m, 1H), 7.65 - 7.62 (m, 1H), 7.46 - 7.38 (m, 2H), 7.03 (d, J = 8.6 Hz, 2H), 6.92 - 6.85 (m, 2H), 4.47 - 4.38 (m, 1H), 4.36 - 4.28 (m, 1H), 3.94 (s, 3H), 3.75 - 3.69 (m, 1H), 3.64 - 3.56 (m, 2H), 3.33 - 3.30 (m, 1H), 3.24 (s, 3H), 3.06 - 2.96 (m, 2H), 2.77 - 2.59 (m, 5H), 2.50 - 2.36 (m, 5H), 2.18 - 2.09 (m, 1H), 2.05 - 1.96 (m, 2H), 1.95 - 1.85 (m, 3H), 1.83 - 1.72 (m, 6H), 1.65 - 1.58 (m, 2H), 1.39 - 1.26 (m, 4H), 1.23 (d, J = 6.7 Hz, 3H)

Example 87. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(((1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)methyl)amino)cyclohexyl)-3-methoxybenzamide (Compound 87)

1. Synthesis of 1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidine-4-carbaldehyde (2)

The title compound (280 mg, crude) was obtained as a pale yellow oil by a similar method to step 2 of Example 56. MS(M+H ₂ O+ H) ⁺ = 319.2

Step 2. Synthesis of tert-butyl (4-(((1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)methyl)amino)cyclohexyl)carbamate (4)

To a solution of 1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidine-4-carbaldehyde (280 mg, 932.24 μmol) in DMF (2 mL) and DCE (8 mL) were added tert-Butyl (4-aminocyclohexyl)carbamate (300 mg, 1.40 mmol) and HOAc (104.90 mg, 1.75 mmol, 100 μL). The mixture was stirred at 20 °C for 1 h. Then, NaBH(OAc) ₃ (840.00 mg, 3.96 mmol) was added at 0 °C, and the mixture was stirred at 20 °C for 15 h. The target mass peak (76%) was confirmed by LCMS. H ₂ O (20 mL) was added to the reaction mixture, diluted with DCM (30 mL), and adjusted to pH = 9 by adding NaHCO ₃ (sat. aq, 40 mL). The mixture was extracted with DCM (40 mL × 2), and the combined organic layer was washed with brine (40 mL × 2), dried over Na ₂ SO ₄ , filtered, and the filtrate was concentrated under reduced pressure to obtain a residue. The residue was purified by prep-HPLC (column: Phenomenex Luna C18 150 x 25 mm x10 μm; mobile phase: [H ₂ O (0.1% TFA) -ACN]; gradient: 0% - 22% B over 15.0 min, column Temp: 30 °C). After lyophilizing the eluate, the compound was diluted with DCM (20 mL) and adjusted to pH = 7~8 with NaHCO ₃ (1 M, 15 mL). The mixture was extracted with DCM (25 mL × 2), concentrated under reduced pressure, and lyophilized to obtain the title compound (260 mg, 521.40 μmol, 55.93% yield) as a pale yellow solid. MS (M+H) ⁺ = 499.4

Step 3. Synthesis of 3-(4-(4-(((4-aminocyclohexyl)amino)methyl)piperidin-1-yl)phenyl)piperidine-2,6-dione (5)

The title compound (120 mg, crude, HCl) was obtained as a pale yellow solid by a similar method to step 4 of Example 42. MS (M+H) ⁺ = 399.3

Step 4. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(((1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)methyl)amino)cyclohexyl)-3-methoxybenzamide (Compound 87)

The title compound (26.9 mg, 33.63 μmol, 15.37% yield, 99% purity) was obtained as a white solid by a similar method to step 3 of Example 59. MS(M+H) ⁺ = 792.5

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.81 - 10.73 (m, 1H), 8.42 (d, J = 8.8 Hz, 1H), 8.06 - 7.96 (m, 1H), 7.90 (s, 1H), 7.62 (s, 1H), 7.55 - 7.48 (m, 2H), 7.04 (d, J = 8.4 Hz, 2H), 6.89 (d, J = 8.6 Hz, 2H), 4.50 - 4.38 (m, 1H), 4.36 - 4.28 (m, 1H), 3.95 (s, 3H), 3.89 - 3.77 (m, 1H), 3.75 - 3.63 (m, 3H), 3.24 (s, 3H), 2.70 - 2.58 (m, 4H), 2.50 - 2.47 (m, 2H), 2.45 - 2.41 (m, 2H), 2.17 - 2.07 (m, 1H), 2.05 - 1.90 (m, 3H), 1.87 - 1.68 (m, 10H), 1.66 - 1.59 (m, 2H), 1.57 - 1.44 (m, 5H), 1.33 - 1.25 (m, 2H), 1.24 (d, J = 6.6 Hz, 3H)

Example 88. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(((1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)methyl)(methyl)amino)cyclohexyl)-3-methoxybenzamide (Compound 88)

The title compound (23.6 mg, 28.69 μmol, 29.63% yield, 98% purity) was obtained as a white solid by a similar method to step 3 of Example 59. MS(M+H) ⁺ =806.5

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.78 (s, 1H), 8.42 (d, J = 8.8 Hz, 1H), 8.04 (d, J = 7.9 Hz, 1H), 7.90 (s, 1H), 7.63 (s, 1H), 7.54 - 7.42 (m, 2H), 7.03 (d, J = 8.6 Hz, 2H), 6.88 (d, J = 8.6 Hz, 2H), 4.51 - 4.39 (m, 1H), 4.32 (q, J = 6.8 Hz, 1H), 3.94 (s, 3H), 3.78 - 3.61 (m, 4H), 3.24 (s, 3H), 2.67 - 2.58 (m, 3H), 2.48 - 2.42 (m, 1H), 2.36 - 2.24 (m, 3H), 2.21 (s, 3H), 2.16 - 2.09 (m, 1H), 2.05 - 1.97 (m, 2H), 1.98 - 1.92 (m, 3H), 1.85 - 1.75 (m, 8H), 1.67 - 1.51 (m, 3H), 1.44 - 1.29 (m, 4H), 1.23 (d, J = 6.6 Hz, 3H), 1.21 - 1.11 (m, 2H).

Example 89. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(((1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)methyl)(methyl)amino)cyclohexyl)-3-(2-hydroxyethoxy)benzamide (Compound 89)

Step 1. Synthesis of (1-(4-bromophenyl)piperidin-4-yl)methanol (3)

The title compound (7.5 g, 27.76 mmol, 78.54% yield) was obtained as a yellow oil by a similar method to step 1 of Example 82. MS(M+H) ⁺ = 270.0, 272.0

Step 2. Synthesis of (1-(4-(2,6-bis(benzyloxy)pyridin-3-yl)phenyl)piperidin-4-yl)methanol (5)

To a solution of (1-( ₄ -bromophenyl)piperidin-4-yl)methanol (6.3 g, 23.32 mmol) and 2,6-dibenzyloxy-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)pyridine (9 g, 21.57 mmol) in dioxane (100 mL) and H 2 O (10 mL) were added Cs ₂ CO ₃ (22.79 g, 69.96 mmol) and Pd(dppf)Cl ₂ (1.71 g, 2.33 mmol), and the resulting mixture was stirred at 100 °C under CN ₂ for 14 h. The target mass peak (42%) was confirmed by LCMS. The mixture was filtered, and the filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (40 g SepaFlash® silica flash column, eluent of 0–50% EtOAc/Commercial hexanes gradient @ 200 mL/min) to give the title compound (7.5 g, 15.61 mmol, 66.92% yield) as a yellow solid. MS(M+H) ⁺ = 481.1

Step 3. Synthesis of 3-(4-(4-(hydroxymethyl)piperidin-1-yl)phenyl)piperidine-2,6-dione (6)

To a solution of (1-(4-(2,6-bis(benzyloxy)pyridin-3-yl)phenyl)piperidin-4-yl)methanol (4 g, 8.32 mmol) in MeOH (20 mL) and THF (20 mL) was added Pd(OH) ₂ /C (0.4 g, 10% purity), and the resulting mixture was stirred at 20 °C under CH ₂ (45 psi) for 14 h. The peak of the target mass (80%) was identified by LCMS, and the mixture was filtered and washed with THF (200 mL). The filtrate was concentrated under reduced pressure to obtain the title compound (2.6 g, crude) as a yellow oil. MS(M+H) ⁺ = 303.2

Step 4. Synthesis of 1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidine-4-carbaldehyde (7)

To a solution of 3-(4-(4-(hydroxymethyl)piperidin-1-yl)phenyl)piperidine-2,6-dione (0.5 g, 1.65 mmol) in DCM (10 mL) was added DMP (1.05 g, 2.48 mmol, 768.48 μL), and the mixture was stirred at 20 °C for 2 h. TLC (Petroleum ether/EtOAc=1/1) confirmed the complete consumption of 3-(4-(4-(hydroxymethyl)piperidin-1-yl)phenyl)piperidine-2,6-dione and the formation of a new spot. The mixture was filtered, and the filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (10 g SepaFlash® silica flash column, Eluent of 0–50% EtOAc/Commercial hexanes gradient @ 100 mL/min) to give the title compound (0.21 g, 671.21 μmol, 40.59% yield, 96% purity) as a yellow oil. MS(M+ _H2O +H) ⁺ = 319.2

Step 5. Synthesis of tert-butyl ((1r,4r)-4-(((1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)methyl)(methyl)amino)cyclohexyl)carbamate (8)

To a solution of 1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidine-4-carbaldehyde (0.1 g, 332.94 μmol) and tert-butyl ((1r,4r)-4-(methylamino)cyclohexyl)carbamate (76.02 mg, 332.94 μmol) in DCM (2 mL) and DMF (2 mL) were added TEA (67.38 mg, 665.89 μmol, 92.68 μL) and MgSO ₄ (80.15 mg, 665.89 μmol), and the mixture was stirred at 20 °C for 1 h. NaBH(OAc) ₃ (211.69 mg, 998.83 μmol) was added, and the mixture was stirred at 20 °C for 14 h. The target mass peak (52%) was identified by LCMS. The mixture was diluted with water (20 mL) and extracted with DCM (20 mL x 3). The combined organic layer was washed with brine (50 mL), dried over Na ₂ SO ₄ , filtered, and the filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (10 g SepaFlash® silica flash column, eluent of 0–10% MeOH/DCM gradient @ 80 mL/min) to give the title compound (50 mg, 97.53 μmol, 29.29% yield) as a yellow oil. MS(M+H) ⁺ = 513.5

Step 6. Synthesis of 3-(4-(4-(((1r,4r)-4-aminocyclohexyl)(methyl)amino)methyl)piperidin-1-yl)phenyl)piperidine-2,6-dione (9)

The title compound (50 mg, crude, HCl) was obtained as a yellow oil by a similar method to step 2 of Example 28. MS(M+H) ⁺ = 413.4

Step 7. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(((1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)methyl)(methyl)amino)cyclohexyl)-3-(2-hydroxyethoxy)benzamide (Compound 89)

The title compound (8.9 mg, 9.26 μmol, 8.32% yield, 87% purity) was obtained as a white solid by a similar method to step 4 of Example 87. MS(M+H) ⁺ = 836.6

^1H NMR (400 MHz, DMSO _- d6 ) δ = 10.78 (s, 1H), 8.43 (d, J = 9.0 Hz, 1H), 8.06 (s, 1H), 8.04 - 7.99 (m, 1H), 7.91 (s, 1H), 7.51 - 7.43 (m, 2H), 7.03 (d, J = 8.6 Hz, 2H), 6.89 (d, J = 8.8 Hz, 2H), 5.19 (t, J = 5.8 Hz, 1H), 4.48 - 4.40 (m, 1H), 4.36 - 4.29 (m, 1H), 4.12 (t, J) = 4.6 Hz, 2H), 3.82 - 3.76 (m, 2H), 3.75 - 3.64 (m, 4H), 3.24 (s, 3H), 2.70 - 2.60 (m, 4H), 2.29 - 2.19 (m, 5H), 2.15 - 2.08 (m, 1H), 2.03 - 1.97 (m, 2H), 1.97 - 1.92 (m, 3H), 1.86 - 1.72 (m, 10H), 1.64 - 1.57 (m, 2H), 1.45 - 1.31 (m, 5H), 1.24 (d, J = 6.6 Hz, 3H), 1.21 - 1.16 (m, 2H).

Example 90. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(((1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)methyl)(methyl)amino)cyclohexyl)-3-methoxybenzamide (Compound 90)

Step 1. Synthesis of tert-butyl ((1r,4r)-4-(((1-(4-(2,6-bis(benzyloxy)pyridin-3-yl)phenyl)piperidin-4-yl)methyl)(methyl)amino)cyclohexyl)carbamate (3)

To a solution of 2,6-bis(benzyloxy)-3-(4-bromophenyl)pyridine (3 g, 6.72 mmol) and tert-butyl ((1r,4r)-4-(methyl(piperidin-4-ylmethyl)amino)cyclohexyl)carbamate (3.28 g, 10.08 mmol) in dioxane (100 mL) were added Pd-PEPPSI-IHeptCl (653.84 mg, 672.14 μmol) and Cs ₂ CO ₃ (6.57 g, 20.16 mmol), and the resulting mixture was stirred at 100 °C under CN ₂ for 28 h. The target mass peak (14%) was identified by LCMS. The mixture was filtered, and the filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (40 g SepaFlash® silica flash column, eluent of 0–100% EtOAc/Petroleum ether gradient @ 100 mL/min) to give the title compound (0.6 g, 868.42 μmol, 12.92% yield) as a yellow solid. MS(M+H) ⁺ = 691.5

Step 2. Synthesis of tert-butyl ((1r,4r)-4-(((1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)methyl)(methyl)amino)cyclohexyl)carbamate (4)

To a solution of _{tert -} butyl ((1r,4r)-4-(((1-(4-(2,6-bis(benzyloxy)pyridin-3-yl)phenyl)piperidin-4-yl)methyl)(methyl)amino)cyclohexyl)carbamate (0.6 g, 868.42 μmol) in CF 3 CH 2 OH (30 mL) were added Pd/C (200 mg, 187.93 μmol, 10% purity) and TFA (153.50 mg, 1.35 mmol, 100 μL) under N ₂ . The resulting mixture was stirred at 20 °C under CH ₂ (45 Psi) for 14 h. The major peak of the desired mass was identified by LCMS. The suspension was filtered through a pad of Celite. The filter cake was washed with CF ₃ CH ₂ OH (100 mL) and the combined filtrates were concentrated under reduced pressure to obtain the title compound (0.9 g, crude, TFA salt) as a yellow oil. MS(M+H) ⁺ = 513.3

Step 3. Synthesis of 3-(4-(4-(((1r,4r)-4-aminocyclohexyl)(methyl)amino)methyl)piperidin-1-yl)phenyl)piperidine-2,6-dione (5)

The title compound (0.5 g, 949.51 μmol, 66.12% yield, TFA salt) was obtained as a yellow oil by a similar method to step 2 of Example 32. MS(M+H) ⁺ = 413.3.

Step 4. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(((1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)methyl)(methyl)amino)cyclohexyl)-3-methoxybenzamide (Compound 90)

The title compound (230.2 mg, 275.11 μmol, 29.26% yield, 98% purity) was obtained as a white solid by a similar method to step 6 of Example 79. MS(M+H) ⁺ =820.5.

^1H NMR (400 MHz, DMSO-d ₆ ) δ = 10.77 (s, 1H), 8.51 - 8.34 (m, 1H), 8.07 - 7.98 (m, 1H), 7.85 (s, 1H), 7.59 (s, 1H), 7.52 - 7.43 (m, 2H), 7.03 (d, J = 8.6 Hz, 2H), 6.89 (d, J = 8.8 Hz, 2H), 4.43 - 4.30 (m, 1H), 4.24 (dd, J = 3.6, 7.6 Hz, 1H), 3.94 (s, 3H), 3.80 - 3.61 (m, 4H), 3.25 (s, 3H), 2.69 - 2.60 (m, 3H), 2.49 - 2.42 (m, 1H), 2.35 - 2.30 (m, 1H), 2.29 - 2.22 (m, 2H), 2.21 (s, 3H), 2.18 - 2.10 (m, 1H), 2.06 - 1.98 (m, 2H), 1.89 - 1.85 (m, 4H), 1.83 - 1.71 (m, 8H), 1.69 - 1.52 (m, 4H), 1.45 - 1.30 (m, 4H), 1.26 - 1.09 (m, 2H), 0.77 (t, J = 7.4 Hz, 3H).

Example 91. 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(((1-(4-((2,6-dioxopiperidin-3-yl)amino)phenyl)piperidin-4-yl)methyl)(methyl)amino)cyclohexyl)-3-methoxybenzamide (Compound 91)

Step 1. Synthesis of tert-butyl ((1r,4r)-4-(methyl((1-(4-nitrophenyl)piperidin-4-yl)methyl)amino)cyclohexyl)carbamate (3)

To a solution of tert-butyl ((1r,4r)-4-(methyl(piperidin-4-ylmethyl)amino)cyclohexyl)carbamate (1 g, 3.07 mmol) and 1-fluoro-4-nitro-benzene (433.50 mg, 3.07 mmol, 325.94 μL) in DMF (20 mL) was added DIPEA (794.15 mg, 6.14 mmol, 1.07 mL), and the resulting mixture was stirred at 20 °C for 14 h. The major peak of the desired mass was identified by LCMS. The mixture was diluted with water (100 mL) and extracted with EtOAc (50 mL x 3). The combined organic layer was washed with brine (100 mL), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure. The residue was triturated with MTBE (30 mL), filtered, and the filter cake was collected to obtain the title compound (0.4 g, 895.69 μmol, 29.15% yield, 100% purity) as a yellow solid. MS(M+H) ⁺ = 447.3

Step 2. Synthesis of tert-butyl ((1r,4r)-4-(((1-(4-aminophenyl)piperidin-4-yl)methyl)(methyl)amino)cyclohexyl)carbamate (4)

The title compound (0.32 g, 768.13 μmol, 85.76% yield) was obtained as a yellow solid by a similar method to step 4 of Example 83. MS(M+H) ⁺ = 417.4

Step 3. Synthesis of tert-butyl ((1r,4r)-4-(((1-(4-((2,6-dioxopiperidin-3-yl)amino)phenyl)piperidin-4-yl)methyl)(methyl)amino)cyclohexyl)carbamate (6)

To a solution of tert-butyl ((1r,4r)-4-(((1-(4-aminophenyl)piperidin-4-yl)methyl)(methyl)amino)cyclohexyl)carbamate (320 mg, 768.13 μmol) and 3-bromopiperidine-2,6-dione (368.72 mg, 1.92 mmol) in ACN (5 mL) were added NaHCO ₃ (322.64 mg, 3.84 mmol, 149.44 μL) and TBAI (50 mg, 135.37 μmol), and the resulting mixture was stirred at 85 °C for 14 h. The major peak of the target mass was identified by LCMS. The mixture was diluted with H ₂ O (30 mL) and MTBE (20 mL) and stirred at 20 °C for 1 h. The mixture was filtered and the filter cake was dried to obtain the title compound as a yellow solid (0.3 g, 568.51 μmol, 74.01% yield). MS(M+H) ⁺ =528.4

Step 4. Synthesis of 3-((4-(4-(((1r,4r)-4-aminocyclohexyl)(methyl)amino)methyl)piperidin-1-yl)phenyl)amino)piperidine-2,6-dione (7)

To a solution of tert-butyl ((1r,4r)-4-(((1-(4-((2,6-dioxopiperidin-3-yl)amino)phenyl)piperidin-4-yl)methyl)(methyl)amino)cyclohexyl)carbamate (150 mg, 284.25 μmol) in DCM (1 mL) was added TFA (1.54 g, 13.46 mmol, 1 mL), and the resulting mixture was stirred at 20 °C for 1 h. The main peak of the desired mass was confirmed by LCMS. The mixture was concentrated under reduced pressure to obtain the title compound (150 mg, 276.95 μmol, 97.43% yield, TFA salt) as a yellow solid. MS(M+H) ⁺ = 428.2

Step 5. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(((1-(4-((2,6-dioxopiperidin-3-yl)amino)phenyl)piperidin-4-yl)methyl)(methyl)amino)cyclohexyl)-3-methoxybenzamide (Compound 91)

To a solution of (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoic acid (60.78 mg, 147.71 μmol) in DMF (3 mL) were added HATU (67.40 mg, 177.25 μmol) and DIPEA (57.27 mg, 443.13 μmol, 77.18 μL), and the mixture was stirred at 20 °C for 0.5 h. 3-((4-(4-(((1r,4r)-4-aminocyclohexyl)(methyl)amino)methyl)piperidin-1-yl)phenyl)amino)piperidine-2,6-dione (80 mg, 147.71 μmol, TFA salt) was added and the mixture was stirred at 20°C for 1 h. The major peak of the desired mass was identified by LCMS. The mixture was diluted with H ₂ O (20 mL) and extracted with EtOAc (10 mL x 3). The combined organic layer was washed with brine (20 mL), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by prep-HPLC (column: Phenomenex Luna C18 150*25 mm*10 um; mobile phase: [H ₂ O (0.1% TFA)-ACN]; gradient: 0%-22% B over 15.0 min), and the eluate was lyophilized. The target product was dissolved in H ₂ O (10 mL) and adjusted to pH=8~9 with NaHCO _3. The resulting suspension was extracted with EtOAc (10 mL x 3), and the combined organic layer was dried over Na ₂ SO ₄ and filtered. The filtrate was concentrated under reduced pressure, and the residue was lyophilized to obtain the title compound (32.9 mg, 36.47 μmol, 24.69% yield, 91% purity) as a white solid. MS(M+H) ⁺ =821.4

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.86 - 10.63 (m, 1H), 8.42 (d, J = 8.9 Hz, 1H), 8.03 (d, J = 7.6 Hz, 1H), 7.90 (s, 1H), 7.62 (s, 1H), 7.51 - 7.43 (m, 2H), 6.75 (d, J = 8.9 Hz, 2H), 6.60 (d, J = 9.0 Hz, 2H), 5.35 (d, J = 7.1 Hz, 1H), 4.48 - 4.38 (m, 1H), 4.32 (q, J = 6.8) Hz, 1H), 4.23 - 4.14 (m, 1H), 3.94 (s, 3H), 3.80 - 3.67 (m, 1H), 3.40 - 3.36 (m, 2H), 3.24 (s, 3H), 2.77 - 2.68 (m, 1H), 2.63 - 2.56 (m, 1H), 2.48 - 2.41 (m, 1H), 2.35 - 2.31 (m, 1H), 2.29 - 2.25 (m, 2H), 2.20 (s, 3H), 2.18 - 2.10 (m, 1H), 2.05 - 1.98 (m, 1H), 1.95 - 1.88 (m, 3H), 1.83 - 1.76 (m, 7H), 1.66 - 1.61 (m, 3H), 1.47 - 1.42 (m, 1H), 1.40 - 1.32 (m, 4H), 1.27 - 1.17 (m, 7H).

Example 92. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(((1-(3-(2,4-dioxotetrahydropyrimidin-1(2H)-yl)-1-methyl-1H-indazol-6-yl)piperidin-4-yl)methyl)(methyl)amino)cyclohexyl)-3-methoxybenzamide (Compound 92)

Step 1. Synthesis of 1-(6-(4-(1,3-dioxolan-2-yl)piperidin-1-yl)-1-methyl-1H-indazol-3-yl)dihydropyrimidine-2,4(1H,3H)-dione (3)

A mixture of 1-(6-bromo-1-methyl-indazol-3-yl)hexahydropyrimidine-2,4-dione (500 mg, 1.55 mmol), 4-(1,3-dioxolan-2-yl)piperidine (292 mg, 1.86 mmol), SPhos Pd G3 (120.7 mg, 154.73 μmol), and t-BuONa (1 M, 4.6 mL) in dioxane (22 mL) was degassed and purged three times under N ₂ , and the mixture was stirred at 90 °C under CN ₂ for 16 h. The desired mass peak (~70%) was identified by LCMS. The mixture was concentrated under reduced pressure, and the residue was purified by flash silica gel chromatography (12 g SepaFlash® silica flash column, Eluent of 0–10% MeOH/EtOAc @ 40 mL/min) to give the title compound as a brown solid (400 mg, 961.34 μmol, 62% yield, 96% purity). MS(M+H) ⁺ = 400.2.

Step 2. Synthesis of 1-(3-(2,4-dioxotetrahydropyrimidin-1(2H)-yl)-1-methyl-1H-indazol-6-yl)piperidine-4-carbaldehyde (4)

A mixture of _1- (6-(4-(1,3-dioxolan-2-yl)piperidin-1-yl)-1-methyl-1H-indazol-3-yl)dihydropyrimidine-2,4(1H,3H)-dione (400 mg, 1.00 mmol) in H 2 O (1 mL), dioxane (1 mL) and HCOOH (6 mL) was stirred at 20 °C under CN ₂ for 48 h. The desired mass peak (~82%) was identified by LCMS. The mixture was adjusted to pH=10 with NaOH (2 N) at 0 °C, extracted with EtOAc (30 mL Х 5), and the combined organic layer was washed with brine (20 mL Х 2), dried over Na ₂ SO ₄ , filtered and concentrated under reduced pressure to give the title compound (270 mg, crude) as a brown solid. MS(M+H) ⁺ =356.2.

Step 3. t Synthesis of tert-butyl ((1r,4r)-4-(((1-(3-(2,4-dioxotetrahydropyrimidin-1(2H)-yl)-1-methyl-1H-indazol-6-yl)piperidin-4-yl)methyl)(methyl)amino)cyclohexyl)carbamate (6)

To a solution of 1-(3-(2,4-dioxotetrahydropyrimidin-1(2H)-yl)-1-methyl-1H-indazol-6-yl)piperidine-4-carbaldehyde (240 mg, 675.31 μmol) and tert-butyl ((1r,4r)-4-(methylamino)cyclohexyl)carbamate (154 mg, 675.31 μmol) in DCM (6 mL) was added AcOH (41 mg, 675.31 μmol), and the mixture was stirred at 20 °C for 1 h, followed by the addition of NaBH(OAc) ₃ (358 mg, 1.69 mmol), and the mixture was stirred at 20 °C for 14 h. The desired mass peak (~84%) was identified by LCMS. The reaction mixture was diluted with water (20 mL), adjusted to pH=9 with saturated NaHCO ₃ , extracted with DCM (100 mL X 3), and the combined organic layers were washed with brine (30 mL X 3), dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (12 g SepaFlash® silica flash column, Eluent of 0–10% MeOH/EtOAc @ 40 mL/min) to give the title compound (240 mg, 405.83 μmol, 60.10% yield, 96% purity) as a pale yellow solid. MS(M+H) ⁺ =568.4.

Step 4. Synthesis of 1-(6-(4-(((1r,4r)-4-aminocyclohexyl)(methyl)amino)methyl)piperidin-1-yl)-1-methyl-1H-indazol-3-yl)dihydropyrimidine-2,4(1H,3H)-dione (7)

The title compound (236 mg, crude, TFA) was obtained as a brown oil by a similar method to step 2 of Example 32. The product was used directly without further purification. MS(M+H) ⁺ = 468.3.

Step 5. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(((1-(3-(2,4-dioxotetrahydropyrimidin-1(2H)-yl)-1-methyl-1H-indazol-6-yl)piperidin-4-yl)methyl)(methyl)amino)cyclohexyl)-3-methoxybenzamide (Compound 92)

The title compound (141.2 mg, 153.61 μmol, 37.86% yield, 95.2% purity) was obtained as a pale yellow solid by a similar method to step 6 of Example 79. MS(M+H) ⁺ =875.5.

¹ H NMR (400 MHz, DMSO- d ₆ ) δ = 10.50 (s, 1H), 8.46 - 8.34 (m, 1H), 8.03 (d, J = 8.0 Hz, 1H), 7.84 (s, 1H), 7.59 (s, 1H), 7.53 - 7.34 (m, 3H), 6.96 - 6.85 (m, 1H), 6.84 - 6.74 (m, 1H), 4.43 - 4.30 (m, 1H), 4.28 - 4.19 (m, 1H), 3.93 (s, 3H), 3.91 - 3.84 (m, 5H), 3.84 - 3.65 (m, 4H), 3.24 (s, 3H), 2.82 - 2.67 (m, 4H), 2.36 - 2.30 (m, 1H), 2.28 - 2.26 (m, 1H), 2.21 (s, 3H), 2.05 - 1.98 (m, 1H), 1.92 - 1.86 (m, 3H), 1.83 - 1.73 (m, 7H), 1.67 - 1.55 (m, 4H), 1.48 - 1.31 (m, 4H), 1.31-1.11 (m, 4H), 0.76 (t, J = 7.6 Hz, 3H).

Example 93. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(3-(((1-(6-(2,6-dioxopiperidin-3-yl)pyridin-3-yl)piperidin-4-yl)methyl)(methyl)amino)cyclobutyl)-3-methoxybenzamide (Compound 93)

Step 1. Synthesis of 2',6'-bis(benzyloxy)-5-bromo-2,3'-bipyridine (3)

To a solution of 5-bromo-2-iodopyridine (5 g, 17.61 mmol) and 2,6-bis(benzyloxy)-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)pyridine (6.61 g, 15.85 mmol) in H ₂ O (20 mL) and dioxane (100 mL) were added K ₂ CO ₃ (7.30 g, 52.84 mmol) and Pd(PPh ₃ ) ₄ (2.04 g, 1.76 mmol), and the mixture was stirred at 80 °C under CN ₂ for 14 h. The desired mass peak (60%) was confirmed by LCMS. The reaction mixture was filtered. The filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (40 g SepaFlash® silica flash column, Eluent of 0–5% EtOAc/Petroleum ether gradient @ 100 mL/min) to give the title compound (5.5 g, 12.05 mmol, 68.41% yield, 98% purity) as a white solid. MS(M+H) ⁺ = 447.0.

Step 2. Synthesis of tert-butyl ((1-(2',6'-bis(benzyloxy)-[2,3'-bipyridin]-5-yl)piperidin-4-yl)methyl)(methyl)carbamate (5)

The title compound (3 g, 5.04 mmol, 75.21% yield, 100% purity) was obtained as a yellow solid of yellow oil by a similar method to step 1 of Example 90. MS(M+H) ⁺ = 595.3

Step 3. Synthesis of tert-butyl ((1-(6-(2,6-dioxopiperidin-3-yl)pyridin-3-yl)piperidin-4-yl)methyl)(methyl)carbamate (6)

The title compound (2.6 g, 4.90 mmol, 97.16% yield, TFA salt) was obtained as a yellow solid of yellow oil by a similar method to step 1 of Example 90. MS(M+H) ⁺ = 417.3

Step 4. Synthesis of 3-(5-(4-((methylamino)methyl)piperidin-1-yl)pyridin-2-yl)piperidine-2,6-dione (7)

The title compound (4 g, crude, TFA salt) as a red oil was obtained by a similar method to step 2 of Example 32. MS(M+H) ⁺ = 317.2

Step 5. Synthesis of tert-butyl (3-(((1-(6-(2,6-dioxopiperidin-3-yl)pyridin-3-yl)piperidin-4-yl)methyl)(methyl)amino)cyclobutyl)carbamate (9)

To a solution of 3-(5-(4-((methylamino)methyl)piperidin-1-yl)pyridin-2-yl)piperidine-2,6-dione (1 g, 2.32 mmol, TFA salt) in DCM (20 mL) were added tert-butyl (3-oxocyclobutyl)carbamate (430.32 mg, 2.32 mmol), TEA (1.18 g, 11.62 mmol, 1.62 mL), and MgSO ₄ (838.95 mg, 6.97 mmol) at 20 °C. After stirring for 1 h, NaBH(OAc) ₃ (738.61 mg, 3.48 mmol) was slowly added, and the reaction mixture was stirred at 20 °C for 12 h. The main peak of the desired mass was confirmed by LCMS. Saturated NaHCO ₃ (100 mL) was added to the reaction mixture and extracted with DCM (50 mL x 3). The combined organic layer was washed with brine (100 mL x 2), dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (20 g SepaFlash® silica flash column, Eluent of 0–100% EtOAc/Petroleum ether gradient @ 80 mL/min) to give the title compound (1.1 g, 2.11 mmol, 90.67% yield, 93% purity) as a yellow oil. MS(M+H) ⁺ = 486.4.

Step 6. Synthesis of 3-(5-(4-(((3-aminocyclobutyl)(methyl)amino)methyl)piperidin-1-yl)pyridin-2-yl)piperidine-2,6-dione (10)

The title compound (1.2 g, crude, HCl salt) was obtained as a yellow solid by a similar method to step 3 of Example 21. MS(M+H) ⁺ = 386.3.

Step 7. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(3-(((1-(6-(2,6-dioxopiperidin-3-yl)pyridin-3-yl)piperidin-4-yl)methyl)(methyl)amino)cyclobutyl)-3-methoxybenzamide (Compound 93)

The title compound (143.2 mg, 169.75 μmol, 14.33% yield, 94% purity) was obtained as a white solid by a similar method to step 6 of Example 79. MS(M+H) ⁺ =793.5.

¹ H NMR (400 MHz, DMSO-d ₆ ) δ = 10.77 (s, 1H), 8.49 - 8.37 (m, 2H), 8.23 - 8.17 (m, 1H), 7.85 (s, 1H), 7.61 (s, 1H), 7.54 - 7.47 (m, 2H), 7.36 - 7.27 (m, 1H), 7.16 (d, J = 8.5 Hz, 1H), 4.44 - 4.28 (m, 2H), 4.29 - 4.21 (m, 1H), 3.95 (s, 3H), 3.42 - 3.96 (m, 1H), 3.79 - 3.68 (m, 2H), 3.25 (s, 3H), 3.05 - 2.85 (m, 1H), 2.78 - 2.69 (m, 2H), 2.61 - 2.56 (m, 1H), 2.48 - 2.39 (m, 1H), 2.25 - 2.01 (m, 11H), 1.93 - 1.73 (m, 9H), 1.70 - 1.59 (m, 4H), 1.30 - 1.12 (m, 2H), 0.77 (t, J = 7.4 Hz, 3H).

Example 94. Synthesis of (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(3-(((1-(3-(2,4-dioxotetrahydropyrimidin-1(2H)-yl)-1-methyl-1H-indazol-6-yl)piperidin-4-yl)methyl)(methyl)amino)cyclobutyl)-3-methoxybenzamide (Compound 94)

Step 1. Synthesis of tert-butyl (3-(((1-(3-(2,4-dioxotetrahydropyrimidin-1(2H)-yl)-1-methyl-1H-indazol-6-yl)piperidin-4-yl)methyl)(methyl)amino)cyclobutyl)carbamate (3)

To a solution of 1-(3-(2,4-dioxotetrahydropyrimidin-1(2H)-yl)-1-methyl-1H-indazol-6-yl)piperidine-4-carbaldehyde (700 mg, 1.97 mmol) and tert-butyl (3-(methylamino)cyclobutyl)carbamate (394 mg, 1.97 mmol) in DCM (20 mL) was added AcOH (118 mg, 1.97 mmol), and the mixture was stirred at 20 °C for 1 h, followed by the addition of NaBH(OAc) ₃ (1.04 g, 4.92 mmol). The mixture was stirred at 20 °C for 14 h. The desired mass peak (46%) was identified by LCMS. The reaction mixture was diluted with water (20 mL), adjusted to pH= ₉ with saturated NaHCO3, extracted with DCM (50 mL X 3), and the combined organic layers were washed with brine (30 mL X ₃ ), dried over _Na2SO4 , filtered and concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (40 g SepaFlash® silica flash column, Eluent of 0–10% MeOH/EtOAc@ 40 mL/min) and prep-HPLC (TFA condition, column: Phenomenex luna C18 150 X 40 mmX 15 um; mobile phase: [water(TFA)-ACN]; gradient: 5%-35% B over 10 min). The extract was lyophilized to obtain the title compound as a white solid (500 mg, 741.94 μmol, 37.67% yield, 97% purity, TFA). MS(M+H) ⁺ =540.4.

Step 2. Synthesis of 1-(6-(4-(((3-aminocyclobutyl)(methyl)amino)methyl)piperidin-1-yl)-1-methyl-1H-indazol-3-yl)dihydropyrimidine-2,4(1H,3H)-dione (4)

The title compound (411 mg, crude, TFA) was obtained as a pale yellow oil by a similar method to step 2 of Example 32. The product was used directly without further purification. MS(M+H) ⁺ = 440.4.

Step 3. Synthesis of (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(3-(((1-(3-(2,4-dioxotetrahydropyrimidin-1(2H)-yl)-1-methyl-1H-indazol-6-yl)piperidin-4-yl)methyl)(methyl)amino)cyclobutyl)-3-methoxybenzamide (Compound 94)

The title compound (160.0 mg, 188.52 μmol, 25.41% yield, 99.8% purity) was obtained as a pale yellow solid by a similar method to step 6 of Example 79. MS(M+H) ⁺ =847.5.

¹ H NMR (400 MHz, DMSO- d ₆ ) δ = 10.49 (s, 1H), 8.51 - 8.36 (m, 2H), 7.85 (s, 1H), 7.60 (s, 1H), 7.53 - 7.50 (m, 1H), 7.49 (s, 1H), 7.45-7.40 (m, 1H), 6.97 - 6.85 (m, 1H), 6.84 - 6.75 (m, 1H), 4.40 - 4.10 (m, 3H), 3.97 - 3.92 (m, 3H), 3.92 - 3.85 (m, 5H), 3.85 - 3.76 (m, 2H), 3.25 (s, 3H), 2.99 - 2.65 (m, 5H), 2.45 - 2.38 (m, 1H), 2.23 - 2.05 (m, 7H), 2.04 - 1.99 (m, 1H), 1.95 - 1.73 (m, 9H), 1.69 - 1.55 (m, 4H), 1.31 - 1.18 (m, 2H), 0.76 (t, J = 7.6 Hz, 3H).

Example 95. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(((1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)amino)methyl)cyclohexyl)-3-methoxybenzamide (Compound 95)

Step 1. Synthesis of tert-butyl (1-(4-(2,6-bis(benzyloxy)pyridin-3-yl)phenyl)piperidin-4-yl)carbamate (3)

A mixture of 2,6-bis(benzyloxy)-3-(4-bromophenyl)pyridine (2.2 g, 4.93 mmol), tert-butyl piperidin-4-ylcarbamate (1.5 g, 7.49 mmol), RuPhos Pd G ₄ (420 mg, 493.89 μmol), and Cs ₂ CO ₃ (4.2 g, 12.89 mmol) in dioxane (80 mL) was degassed and purged three times with N ₂ , and the mixture was stirred at 100 °C under CN ₂ for 16 h. The target mass peak (59%) was identified by LCMS. The reaction mixture was filtered, washed with EtOAc (100 mL), and the filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (20 g SepaFlash® silica flash column, eluent of 15–30% EtOAc: petroleum ether gradient, 120 mL/min) to give the title compound (2 g, 3.54 mmol, 71.73% yield) as a white solid. MS(M+H) ⁺ = 566.4

Step 2. Synthesis of tert-butyl (1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)carbamate (4)

A solution of Pd/C (3.00 g, 2.82 mmol, 10% purity) in CF ₃ CH ₂ OH (30 mL) was slowly added to a solution of tert-butyl (1-(4-(2,6-bis(benzyloxy)pyridin-3-yl)phenyl)piperidin-4-yl)carbamate (1.2 g, 2.12 mmol) and HOAc (251.76 mg, 4.19 mmol, 240 μL) in THF (30 mL) under N ₂ , and the mixture was stirred at 25 °C under CH ₂ (15 Psi) for 16 h. The target mass peak (28%) was identified by LCMS. The mixture was filtered, the filter cake was washed with CF ₃ CH ₂ OH (30 mL), and the filtrate was concentrated under reduced pressure. The residue was purified by prep-HPLC (column: Phenomenex Luna C18 150 x 25 mm x10 μm; mobile phase: [H ₂ O (0.1% TFA) -ACN]; gradient: 0% - 28% B over 15.0 min; column Temp: 30 °C) and the eluate was lyophilized to give the title compound (400 mg, 1.03 mmol, 48.67% yield) as a yellow solid. MS(M+H) ⁺ = 388.2

Step 3. Synthesis of 3-(4-(4-aminopiperidin-1-yl)phenyl)piperidine-2,6-dione (5)

To a solution of tert-butyl (1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)carbamate (300 mg, 774.25 μmol) in dioxane (5 mL) was added HCl/dioxane (2 M, 15.00 mL). The mixture was stirred at 20 °C under CN ₂ for 16 h. The peak of the desired mass was identified by LCMS. The reaction mixture was concentrated under reduced pressure to obtain the title compound (250 mg, crude, HCl) as a yellow solid. MS(M+H) ⁺ = 288.1

Step 4. Synthesis of tert-butyl ((1r,4r)-4-(((1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)amino)methyl)cyclohexyl)carbamate (7)

To a solution of 3-(4-(4-aminopiperidin-1-yl)phenyl)piperidine-2,6-dione (250 mg, 772.04 μmol, HCl) in DCM (10 mL) and DMF (2 mL) were added tert-Butyl ((1r,4r)-4-formylcyclohexyl)carbamate (175 mg, 769.91 μmol) and TEA (436.20 mg, 4.31 mmol, 600 μL), and the mixture was stirred at 20 °C for 1 h. Then, NaBH(OAc) ₃ (700 mg, 3.30 mmol) was added to the mixture at 0 °C, and the mixture was stirred at 20 °C for 15 h. The peak of the target mass (61%) was confirmed by LCMS. H ₂ O (15 mL) was added to the reaction mixture, diluted with DCM (30 mL), and adjusted to pH = 9 with NaHCO ₃ (sat. aq, 15 mL). The mixture was extracted with DCM (30 mL × 2), and the combined organic layer was washed with brine (30 mL × 2), dried over Na ₂ SO ₄ , filtered, and the filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (12 g SepaFlash® silica flash column, eluent of 5–20% ethanol: DCM 120 mL/min) to give the title compound (180 mg, 360.97 μmol, 46.76% yield) as a yellow solid. MS (M+H) ⁺ = 499.4

Step 5. Synthesis of 3-(4-(4-(((1r,4r)-4-aminocyclohexyl)methyl)amino)piperidin-1-yl)phenyl)piperidine-2,6-dione (8)

To a solution of tert-butyl ((1r,4r)-4-(((1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)amino)methyl)cyclohexyl)carbamate (100 mg, 200.54 μmol) in dioxane (3 mL) was added HCl/dioxane (2 M, 15 mL). The mixture was stirred at 20 °C under CN ₂ for 16 h. The peak of the desired mass was identified by LCMS. The reaction mixture was concentrated under reduced pressure to obtain the title compound (87 mg, crude, HCl) as a yellow solid. MS(M+H) ⁺ = 399.3

Step 6. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(((1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)amino)methyl)cyclohexyl)-3-methoxybenzamide (Compound 95)

To a solution of (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoic acid (70 mg, 170.13 μmol) in DMF (2 mL) were added HATU (80 mg, 210.40 μmol) and DIPEA (148.40 mg, 1.15 mmol, 200 μL), and the mixture was stirred at 20 °C for 0.5 h, after which a solution of 3-(4-(4-((((1r,4r)-4-aminocyclohexyl)methyl)amino)piperidin-1-yl)phenyl)piperidine-2,6-dione (87 mg, 218.30 μmol, HCl) in DMF (2 mL) was added to the mixture at 0 °C. The mixture was stirred at 20 °C under CN ₂ for 15.5 h. The peak of the target mass (73%) was identified by LCMS. The reaction mixture was diluted with H ₂ O (15 mL), and the mixture was extracted with EtOAc (30 mL × 2). The combined organic layers were washed with NaHCO ₃ (aq, 30 mL × 2) and brine (30 mL × 2), dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure. The residue was purified by prep-HPLC (column: Phenomenex Luna C18 150 x 25 mm x10 μm; mobile phase: [H ₂ O (0.1% TFA) -ACN]; gradient: 0% - 30% B over 15.0 min, column Temp: 30 °C). The eluate was diluted with DCM (15 mL) and adjusted to pH = 7~8 with NaHCO ₃ (1 M, 15 mL). The mixture was extracted with DCM (15 mL × 2), concentrated under reduced pressure, and lyophilized to obtain the title compound (39 mg, 46.29 μmol, 27.21% yield, 94% purity) as a white solid. MS (M+H) ⁺ = 792.5

¹ H NMR (400 MHz, DMSO- d ₆ ) δ = 10.88 - 10.70 (m, 1H), 8.48 - 8.37 (m, 1H), 8.10 - 8.01 (m, 1H), 7.90 (s, 1H), 7.63 (s, 1H), 7.54 - 7.46 (m, 2H), 7.03 (d, J = 8.7 Hz, 2H), 6.88 (d, J = 8.8 Hz, 2H), 4.48 - 4.38 (m, 1H), 4.32 (q, J = 6.7 Hz, 1H), 3.95 (s, 3H), 3.81 - 3.69 (m, 2H), 3.65 - 3.55 (m, 2H), 3.24 (s, 3H), 2.76 - 2.66 (m, 2H), 2.65 - 2.58 (m, 1H), 2.50 - 2.39 (m, 4H), 2.17 - 2.08 (m, 1H), 2.07 - 1.98 (m, 2H), 1.95 - 1.74 (m, 11H), 1.67 - 1.56 (m, 2H), 1.44 - 1.26 (m, 6H), 1.23 (d, J = 6.7 Hz, 3H), 1.05 - 0.93 (m, 2H)

Example 96. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(((1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)(methyl)amino)methyl)cyclohexyl)-3-methoxybenzamide (Compound 96)

Step 1. Synthesis of tert-butyl (4-(((1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)(methyl)amino)methyl)cyclohexyl)carbamate (2)

To a solution of tert-butyl (4-(((1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)amino)methyl)cyclohexyl)carbamate (80.00 mg, 160.43 μmol) in DCM (5 mL) and MeOH (5 mL) were added aldehyde (130 mg, 1.60 mmol, 119.27 μL) and HOAc (20.00 mg, 333.05 μmol, 19.07 μL), and the mixture was stirred at 20 °C for 1 h. Then, NaBH ₃ CN (60.49 mg, 962.59 μmol) was added to the mixture at 0 °C, and the mixture was stirred at 20 °C for 15 h. The major peak of the target mass was identified by LCMS. After adding H ₂ O (10 mL) to the reaction mixture, the mixture was concentrated under reduced pressure to remove MeOH and DCM. Diluted with DCM (30 mL), adjusted to pH = 9 by adding NaHCO ₃ (sat.aq, 40 mL), and the mixture was extracted with DCM (50 mL × 2). The combined organic layer was then washed with brine (50 mL × 2), dried over Na ₂ SO ₄ , filtered, and the filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (12 g SepaFlash® silica flash column, eluent of 5–20% ethanol: DCM 120 mL/min) to give the title compound (82 mg, 159.94 μmol, 99.70% yield) as a yellow solid. MS (M+ H) ⁺ = 513.4

Step 2. Synthesis of 3-(4-(4-(((4-aminocyclohexyl)methyl)(methyl)amino)piperidin-1-yl)phenyl)piperidine-2,6-dione (3)

To a solution of tert-butyl (4-(((1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)(methyl)amino)methyl)cyclohexyl)carbamate (82 mg, 159.94 μmol) in dioxane (2 mL) was added HCl/dioxane (2 M, 10 mL). The mixture was stirred at 20 °C under CN ₂ for 16 h. The peak of the desired mass was identified by LCMS. The reaction mixture was concentrated under reduced pressure to obtain the title compound (71 mg, crude, HCl) as a pale yellow solid. MS(M+H) ⁺ = 413.4

Step 3. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(((1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)(methyl)amino)methyl)cyclohexyl)-3-methoxybenzamide (Compound 96)

To a solution of (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoic acid (70.00 mg, 170.13 μmol) in DMF (2 mL) were added HATU (80.00 mg, 210.40 μmol) and DIPEA (148.40 mg, 1.15 mmol, 200 μL), and the mixture was stirred at 20 °C for 0.5 h, after which a solution of 3-(4-(4-(((4-aminocyclohexyl)methyl)(methyl)amino)piperidin-1-yl)phenyl)piperidine-2,6-dione (71 mg, 158.12 μmol, HCl) in DMF (2 mL) was added to the mixture at 0 °C. The mixture was stirred at 20 °C under CN ₂ for 15.5 h. The peak of the target mass (74%) was confirmed by LCMS. The reaction mixture was diluted with H ₂ O (15 mL), and the mixture was extracted with EtOAc (30 mL × 2). The combined organic layer was washed with NaHCO ₃ (aq, 30 mL × 2), brine (30 mL × 2), dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure. The residue was purified by prep-HPLC (column: Phenomenex Luna C18 150 x 25 mm x 10 μm; mobile phase: [H 2 O (0.1% TFA) -ACN]; gradient: 0% - 30% B over 15.0 min, column Temp: 30 °C). After lyophilization of the extract, the compound was diluted with DCM (15 mL), and the pH was adjusted to 7–8 by adding NaHCO ₃ (1 M, 10 mL). The mixture was extracted with DCM (15 mL × 2), concentrated under reduced pressure, and lyophilized to obtain the title compound (65.0 mg, 79.84 μmol, 46.93% yield, 99% purity) as a white solid. MS (M+H) ⁺ = 806.6

¹ H NMR (400 MHz, DMSO- d ₆ ) δ = 10.83 - 10.72 (m, 1H), 8.46 - 8.33 (m, 1H), 8.08 - 8.00 (m, 1H), 7.85 (s, 1H), 7.62 (s, 1H), 7.52 - 7.43 (m, 2H), 7.03 (d, J = 8.4 Hz, 2H), 6.88 (d, J = 8.7 Hz, 2H), 4.48 - 4.38 (m, 1H), 4.35 - 4.28 (m, 1H), 3.94 (s, 3H), 3.79 - 3.65 (m, 4H), 3.23 (s, 3H), 2.69 - 2.57 (m, 3H), 2.47 - 2.36 (m, 2H), 2.27 - 2.16 (m, 5H), 2.15 - 2.07 (m, 1H), 2.04 - 1.94 (m, 2H), 1.93 - 1.69 (m, 11H), 1.66 - 1.57 (m, 2H), 1.55 - 1.43 (m, 2H), 1.40 - 1.28 (m, 3H), 1.23 (d, J = 6.7 Hz, 3H), 0.99 - 0.86 (m, 2H).

Example 97. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(7-((1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)methyl)-2,7-diazaspiro[3.5]nonan-2-yl)-3-methoxybenzamide (Compound 97)

Step 1. Synthesis of 7-benzyl 2-(tert-butyl) 2,7-diazaspiro[3.5]nonane-2,7-dicarboxylate (2)

To a solution of tert-butyl 2,7-diazaspiro[3.5]nonane-2-carboxylate (3 g, 11.42 mmol, HCl salt) in DCM (30 mL) was added TEA (3.47 g, 34.25 mmol, 4.77 mL) at 0 °C. Then, a solution of CbzCl (2.92 g, 17.12 mmol, 2.44 mL) in DCM (10 mL) was added at 0 °C, and the resulting mixture was stirred at 20 °C for 12 h. LCMS confirmed complete consumption of the starting material and the peak of the target mass (20%). The reaction mixture was diluted with H ₂ O (60 mL) and extracted with DCM (30 mL x 3). The organic layer was dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (40 g SepaFlash® silica flash column, eluent of 12–20% EtOAc/Petroleum ether gradient @ 200 mL/min) to give the title compound (3 g, 8.32 mmol, 72.90% yield) as a yellow oil. MS(M+H) ⁺ = 361.3

Step 2. Synthesis of benzyl 2,7-diazaspiro[3.5]nonane-7-carboxylate (3)

To a solution of 7-benzyl 2-(tert-butyl) 2,7-diazaspiro[3.5]nonane-2,7-dicarboxylate (3 g, 8.32 mmol) in DCM (20 mL) was added TFA (7.42 mL) at 20 °C, and the resulting mixture was stirred at 20 °C for 1 h. LCMS confirmed complete consumption of the starting material and the peak of the target mass (65%). The reaction mixture was concentrated under reduced pressure to obtain the title compound (3.2 g, crude, TFA salt) as a yellow oil. MS (M-100+H) ⁺ = 261.3

Step 3. Synthesis of benzyl 2-nitroso-2,7-diazaspiro[3.5]nonane-7-carboxylate (4)

To a solution of benzyl 2,7-diazaspiro[3.5]nonane-7-carboxylate (3.2 g, 8.55 mmol, TFA) in _H2O (40 mL) was added _NaNO2 (1.77 g, 25.64 mmol) at 0 °C. AcOH (2.05 g, 34.19 mmol, 1.96 mL) was then added at 0 °C, and the resulting mixture was stirred at 20 °C for 12 h. LCMS confirmed 67% of the starting material and a peak of the target mass (27%). The resulting mixture was stirred at 20 °C for 2 h. LCMS confirmed 40% of the starting material remaining and a peak of the target mass (43%). Additionally, NaNO ₂ (1.77 g, 25.64 mmol) and AcOH (2.05 g, 34.19 mmol, 1.96 mL) were added, and the reaction mixture was stirred at 20 °C for an additional 14 h. LCMS confirmed the remaining starting material and the peak of the target mass (53%). Saturated Na ₂ CO ₃ was added to the reaction mixture, adjusted to about pH 10, and extracted with EtOAc (30 mL x 3). The organic layer was dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure to give the title compound (2 g, 6.91 mmol, 80.87% yield) as a yellow oil.

Step 4. Synthesis of benzyl 2-((tert-butoxycarbonyl)amino)-2,7-diazaspiro[3.5]nonane-7-carboxylate (6)

To a solution of benzyl 2-nitroso-2,7-diazaspiro[3.5]nonane-7-carboxylate (2 g, 6.91 mmol) in THF (20 mL) and H ₂ O (10 mL) was added NH ₄ Cl (2.22 g, 41.48 mmol) at 0 °C. Zn (1.36 g, 20.74 mmol) was then added at 0 °C, and the resulting mixture was stirred at 20 °C for 1 h. LCMS confirmed complete consumption of the starting material and the peak of benzyl 2-amino-2,7-diazaspiro[3.5]nonane-7-carboxylate (53%). Afterwards, NaOH (1.66 g, 41.48 mmol) and (Boc) ₂ O (2.26 g, 10.37 mmol, 2.38 mL) were added at 20 °C, and the resulting mixture was stirred at 20 °C for an additional 12 h. After confirming that the starting material remained and the peak of the target mass by LCMS, the resulting mixture was stirred at 20 °C for 12 h. LCMS confirmed that the starting material remained and the peak of the target mass. The reaction mixture was diluted with H ₂ O (50 mL) and extracted with EtOAc (30 mL x 3). The organic layer was dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (40 g SepaFlash® silica flash column, eluent of 12–40% EtOAc/Petroleum ether gradient @ 200 mL/min) to obtain the title compound (166 mg, 442.12 μmol, 6.40% yield) as a yellow oil. MS(M+H) ⁺ = 376.2

Step 5. Synthesis of benzyl 2-amino-2,7-diazaspiro[3.5]nonane-7-carboxylate (7)

To a solution of benzyl 2-((tert-butoxycarbonyl)amino)-2,7-diazaspiro[3.5]nonane-7-carboxylate (166 mg, 442.12 μmol) in DCM (4 mL) was added TFA (394.10 μL) at 20 °C, and the resulting mixture was stirred at 20 °C for 2 h. LCMS confirmed complete consumption of the starting material and the peak of the target mass (38%). The reaction mixture was concentrated under reduced pressure to obtain the title compound (173 mg, crude, TFA salt) as a yellow oil. MS(M+H) ⁺ = 276.0

Step 6. Synthesis of benzyl (R)-2-(4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzamido)-2,7-diazaspiro[3.5]nonane-7-carboxylate (9)

To a solution of (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoic acid (60 mg, 145.82 μmol) in DMF (2 mL) was added HATU (66.54 mg, 174.99 μmol) and DIPEA (188.47 mg, 1.46 mmol, 254.00 μL) at 20 °C. After stirring for 10 min, benzyl 2-amino-2,7-diazaspiro[3.5]nonane-7-carboxylate (86.43 mg, 221.97 μmol, TFA) was added at 20 °C, and the resulting mixture was stirred at 20 °C for 1 h. The peak of the target mass (49%) was confirmed by LCMS. The reaction mixture was diluted with H ₂ O (30 mL) and extracted with EtOAc (20 mL x 3). The organic layer was washed with brine (20 mL x 3), dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (10 g SepaFlash® silica flash column, eluent of 50–100% EtOAc/Petroleum ether to 10–10% MeOH/DCM gradient @ 200 mL/min) to give the title compound (59 mg, 88.22 μmol, 60.50% yield) as a yellow solid. MS(M+H) ⁺ = 669.3

Step 7. Synthesis of (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxy-N-(2,7-diazaspiro[3.5]nonan-2-yl)benzamide (10)

Benzyl (R)-2-(4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzamido)-2,7-diazaspiro[3.5]nonane-7-carboxylate (59 mg, 88.22 μmol) was dissolved in TFA (4 mL) at 20 °C, and the resulting mixture was stirred at 40 °C for 12 h. LCMS confirmed complete consumption of the starting material and the peak of the target mass (65%). The reaction mixture was concentrated under reduced pressure to obtain the title compound (58 mg, crude, TFA) as a yellow oil. MS(M+H) ⁺ = 535.3

Step 8. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(7-((1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)methyl)-2,7-diazaspiro[3.5]nonan-2-yl)-3-methoxybenzamide (Compound 97)

To a solution of (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxy-N-(2,7-diazaspiro[3.5]nonan-2-yl)benzamide (58 mg, 89.41 μmol, TFA salt) and 1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidine-4-carbaldehyde (40.28 mg, 134.12 μmol) in DCM (4 mL) and DMF (2 mL) were added TEA (90.48 mg, 894.13 μmol, 124.45 μL) and MgSO ₄ (16.14 mg, 134.12 μmol) at 20 °C. After stirring for 1 h, NaBH(OAc) ₃ (56.85 mg, 268.24 μmol) was added at 20 °C, and the resulting mixture was stirred at 20 °C for 12 h. Complete consumption of the starting material and the peak of the target mass (53%) were confirmed by LCMS. The reaction mixture was diluted with H ₂ O (20 mL) and extracted with DCM (20 mL x 3). The organic layer was dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure. The residue was purified by prep-HPLC (column: Phenomenex Luna C18 150*25 mm*10 μm; mobile phase: [H ₂ O (0.1% TFA) - ACN]; gradient: 0% - 25% B over 15.0 min). The eluate was adjusted to about pH 8 by adding saturated NaHCO ₃ and extracted with DCM (20 mL x 2). The organic layer was dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure. The product was dissolved in a mixed solution (20 mL, ACN: H ₂ O = 1:1) and lyophilized to obtain the title compound as a white solid (8.9 mg, 9.67 μmol, 10.82% yield, 89% purity). MS(M+H) ⁺ = 819.7

^1H NMR (400 MHz, DMSO-d ₆ ) δ = 10.76 (s, 1H), 9.47 (s, 1H), 8.47 - 8.37 (m, 1H), 7.89 (s, 1H), 7.65 - 7.59 (m, 1H), 7.45 - 7.36 (m, 2H), 7.02 (d, J = 8.6 Hz, 2H), 6.87 (br d, J = 8.8 Hz, 2H), 4.47 - 4.37 (m, 1H), 4.35 - 4.28 (m, 1H), 3.93 (s, 3H), 3.71 (dd, J = 5.1, 10.9 Hz, 1H), 3.68 - 3.60 (m, 2H), 3.23 (s, 3H), 2.66 - 2.57 (m, 3H), 2.46 - 2.41 (m, 1H), 2.31 - 2.21 (m, 3H), 2.10 (br d, J = 6.0 Hz, 2H), 2.03 - 1.97 (m, 2H), 1.95 - 1.88 (m, 1H), 1.85 - 1.73 (m, 8H), 1.68 - 1.56 (m, 4H), 1.23 (br d, J = 6.6 Hz, 3H), 1.17 (br s, 4H), 0.87 - 0.83 (m, 1H), 0.79 - 0.70 (m, 4H)

Example 98. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(7-((1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)methyl)-2,7-diazaspiro[3.5]nonan-2-yl)-3-(2-hydroxyethoxy)benzamide (Compound 98)

Step 1. Synthesis of tert-butyl 2-nitroso-2,7-diazaspiro[3.5]nonane-7-carboxylate (2)

To a solution of tert-butyl 2,7-diazaspiro[3.5]nonane-7-carboxylate (5 g, 22.09 mmol) in _H2O (50 mL) was added _NaNO2 (4.57 g, 66.28 mmol) at 20 °C. AcOH (5.31 g, 88.37 mmol, 5.06 mL) was then added at 20 °C, and the resulting mixture was stirred at 20 °C for 12 h. The target mass peak (91%) was confirmed by LCMS. The reaction mixture was diluted with _H2O (100 mL), and the pH was adjusted to ₁₀ with saturated _Na2CO3 . The suspension was extracted with EtOAc (100 mL x 3). The organic layer was dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure to obtain the title compound (4.8 g, 18.80 mmol, 85.10% yield) as a white solid. MS (M-56+H) ⁺ = 200.1

Step 2. Synthesis of tert-butyl 2-(((benzyloxy)carbonyl)amino)-2,7-diazaspiro[3.5]nonane-7-carboxylate (4)

To a solution of tert-butyl 2-nitroso-2,7-diazaspiro[3.5]nonane-7-carboxylate (4.8 g, 18.80 mmol) in THF (30 mL) and H ₂ O (10 mL) was added NH ₄ Cl (7.04 g, 131.60 mmol) at 0 °C. Zn (6.15 g, 94.00 mmol) was then added at 0 °C, and the resulting mixture was stirred at 20 °C for 2 h. The reaction mixture was filtered, and the filter cake was washed with THF (30 mL x 3). To the filtrate, NaOH (4.51 g, 112.80 mmol) and CbzCl (4.81 g, 28.20 mmol, 4.03 mL) were added at 0 °C, and the resulting mixture was stirred at 20 °C for 12 h. LCMS confirmed complete consumption of the starting material and the peak of the target mass (32%). The reaction mixture was diluted with H ₂ O (80 mL) and extracted with EtOAc (40 mL x 3). The organic layer was dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (10 g SepaFlash® silica flash column, eluent of 5–15% EtOAc/Petroleum ether gradient @ 200 mL/min) to give the title compound (9.4 g, crude) as a white solid. MS(M+H) ⁺ = 376.2

Step 3. Synthesis of benzyl (2,7-diazaspiro[3.5]nonan-2-yl)carbamate (5)

To a solution of tert-butyl 2-(((benzyloxy)carbonyl)amino)-2,7-diazaspiro[3.5]nonane-7-carboxylate (0.6 g, 1.60 mmol) in DCM (4 mL) was added TFA (1.42 mL) at 20 °C, and the resulting mixture was stirred at 20 °C for 12 h. LCMS confirmed complete consumption of the starting material and the peak of the target mass (44%). The reaction mixture was concentrated under reduced pressure to obtain the title compound (623 mg, crude, TFA salt) as a yellow oil. MS(M+H) ⁺ = 276.1

Step 4. Synthesis of benzyl (7-((1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)methyl)-2,7-diazaspiro[3.5]nonan-2-yl)carbamate (7)

To a solution of 1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidine-4-carbaldehyde (250 mg, 832.36 μmol) and benzyl (2,7-diazaspiro[3.5]nonan-2-yl)carbamate (623 mg, 1.60 mmol, TFA salt) in DCM (12 mL) and DMF (2 mL) was added TEA (842.25 mg, 8.32 mmol, 1.16 mL) at 20 °C. The mixture was stirred for 0.5 h, after which NaBH(OAc) ₃ (529.23 mg, 2.50 mmol) was added at 20 °C, and the resulting mixture was stirred at 20 °C for 12 h. LCMS confirmed complete consumption of the starting material and the peak of the target mass (65%). The reaction mixture was diluted with H ₂ O (20 mL) and extracted with DCM (20 mL x 3). The organic layer was washed with saturated NaHCO ₃ (20 mL x 3), dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (12 g SepaFlash® silica flash column, Eluent of 50–100% EtOAc/Petroleum ether to 10–10% MeOH/DCM gradient @ 200 mL/min) and repurified by prep-HPLC (Column: Phenomenex Luna C18 150*25 mm*10um; Mobile phase: [H ₂ O (0.1% TFA) - ACN]; Gradient: 0% - 22% B over 15.0 min). The eluate was adjusted to pH= ₈ with saturated NaHCO3, and then extracted with DCM (20 mL x 2). The organic layer was dried _{over Na2SO4} , filtered, and concentrated under reduced pressure to obtain the title compound (221 mg, 394.86 μmol, 47.44% yield) as a white solid. MS(M+H) ⁺ =560.4

Step 5. Synthesis of 3-(4-(4-((2-amino-2,7-diazaspiro[3.5]nonan-7-yl)methyl)piperidin-1-yl)phenyl)piperidine-2,6-dione (8)

Benzyl (7-((1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)methyl)-2,7-diazaspiro[3.5]nonan-2-yl)carbamate (221 mg, 394.86 μmol) was dissolved in TFA (6 mL) at 20 °C, and the resulting mixture was stirred at 40 °C for 12 h. LCMS confirmed complete consumption of the starting material and the peak of the target mass (61%). The reaction mixture was concentrated under reduced pressure to obtain the title compound (214 mg, crude, TFA salt) as a yellow oil. MS(M+H) ⁺ = 426.3

Step 6. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(7-((1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)methyl)-2,7-diazaspiro[3.5]nonan-2-yl)-3-(2-hydroxyethoxy)benzamide (Compound 98)

To a solution of (R)-4-((8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-(2-hydroxyethoxy)benzoic acid (100 mg, 226.51 μmol) in DMF (8 mL) was added HATU (103.35 mg, 271.81 μmol) and DIPEA (351.29 mg, 2.72 mmol, 473.44 μL) at 20 °C. The mixture was stirred for 10 min. Afterwards, a solution of 3-(4-(4-((2-amino-2,7-diazaspiro[3.5]nonan-7-yl)methyl)piperidin-1-yl)phenyl)piperidine-2,6-dione (214 mg, 396.60 μmol, TFA salt) was added at 20 °C, and the resulting mixture was stirred at 20 °C for 2 h. Complete consumption of the starting material and a peak of the target mass (54%) were confirmed by LCMS. The reaction mixture was diluted with H ₂ O (30 mL), and extracted with EtOAc (20 mL x 3). The organic layer was dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure. The residue was purified by prep-HPLC (column: Phenomenex Luna C18 150*25 mm*10um; mobile phase: [H ₂ O (0.1% TFA) - ACN]; gradient: 0% - 22% B over 15.0 min) to obtain two batches of eluates. The two batches were adjusted to pH=8 with saturated NaHCO ₃ and extracted with DCM (20 mL x 2). The organic layer was dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure, respectively. The two batches of product were dissolved in a mixed solution (20 mL, ACN:H ₂ O = 1:1) and lyophilized to obtain the title compound as a white solid (28.8 mg, 31.21 μmol, 13.78% yield, 92% purity) and the title compound as a white solid (15.2 mg, 16.83 μmol, 7.43% yield, 94% purity). MS(M+H) ⁺ =849.4

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.75 (m, 1H), 9.53 - 9.38 (m, 1H), 8.89 - 8.43 (m, 1H), 8.07 (s, 1H), 7.90 (s, 1H), 7.43 - 7.35 (m, 2H), 7.02 (br d, J = 8.5 Hz, 2H), 6.87 (br d, J = 8.6 Hz, 2H), 5.29 - 4.99 (m, 1H), 4.42 (quin, J = 8.1 Hz, 1H), 4.32 (q, J = 6.8 Hz, 1H), 4.11 (br t, J = 4.1 Hz, 2H), 3.78 (br t, J = 4.2 Hz, 2H), 3.71 (br dd, J = 4.9, 10.8 Hz, 1H), 3.64 (br d, J = 12.1 Hz, 2H), 3.54 - 3.50 (m, 2H), 3.24 (s, 3H), 2.67 - 2.58 (m, 3H), 2.48 - 2.41 (m, 1H), 2.34 - 2.16 (m, 4H), 2.14 - 2.06 (m, 3H), 2.04 - 1.97 (m, 2H), 1.92 (br d, J = 7.5 Hz, 1H), 1.78 (br d, J = 5.3 Hz, 3H), 1.74 (br s, 4H), 1.67 - 1.56 (m, 4H), 1.23 (br d, J = 6.8 Hz, 3H), 1.20 - 1.11 (m, 4H), 0.89 - 0.82 (m, 1H), 0.80 - 0.72 (m, 1H)

Example 99. Synthesis of 4-(((R)-7,8-diethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(7-((1-(4-(2,6-dioxopiperidin-3-yl)-2-fluorophenyl)piperidin-4-yl)methyl)-2,7-diazaspiro[3.5]nonan-2-yl)-3-methoxybenzamide (Compound 99)

Step 1. Synthesis of tert-butyl (2,7-diazaspiro[3.5]nonan-2-yl)carbamate (2)

To a solution of benzyl 2-((tert-butoxycarbonyl)amino)-2,7-diazaspiro[3.5]nonane-7-carboxylate (1.50 g, 4.00 mmol) in CF ₃ CH ₂ OH (25 mL) and AcOH (2.5 mL) was added Pd/C (400 mg, 375.87 μmol, 10% purity) under N ₂ . The suspension was degassed and purged three times under H ₂ . The mixture was stirred at 25 °C under CH ₂ (15 Psi) for 16 h. The major peak of the desired mass was identified by LCMS. The mixture was diluted with CF ₃ CH ₂ OH (100 ml) and filtered. The filtrate was concentrated under reduced pressure to obtain the title compound (1.20 g, 3.98 mmol, 99.66% yield, HOAc) as a pale yellow oil. MS(M+H) ⁺ =242.2.

Step 2. Synthesis of tert-butyl (7-((1-(4-(2,6-dioxopiperidin-3-yl)-2-fluorophenyl)piperidin-4-yl)methyl)-2,7-diazaspiro[3.5]nonan-2-yl)carbamate (3)

To a solution of 1-(4-(2,6-dioxopiperidin-3-yl)-2-fluorophenyl)piperidine-4-carbaldehyde (300 mg, 942.38 μmol) and tert-butyl (2,7-diazaspiro[3.5]nonan-2-yl)carbamate (426 mg, 1.41 mmol, HOAc) in DCM (10 mL) was added AcOH (57 mg, 942.38 μmol). The mixture was stirred at 20 °C for 1 h. NaBH(OAc) ₃ (399 mg, 1.88 mmol) was added, and the mixture was stirred at 20 °C for 14 h. The desired mass peak (95%) was confirmed by LCMS. The reaction mixture was diluted with water (20 mL), adjusted to pH= ₉ with saturated NaHCO3, and extracted with DCM (30 mL X 3). The combined organic layer was washed with brine (20 mL X 2), dried _{over Na2SO4} , filtered, and concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (12 g SepaFlash® silica flash column, Eluent of 70–80% EtOAc/Petroleum ether gradient @ 60 mL/min) to give the title compound (140 mg, 236.91 μmol, 25.14% yield, 92% purity) as a brown solid. MS(M+H) ⁺ =544.4.

Step 3. Synthesis of 3-(4-(4-((2-amino-2,7-diazaspiro[3.5]nonan-7-yl)methyl)piperidin-1-yl)-3-fluorophenyl)piperidine-2,6-dione (4)

The title compound (132 mg, 236.74 μmol, 99.93% yield, TFA) was obtained as a brown oil by a similar method to step 2 of Example 32. MS(M+H) ⁺ = 444.2.

Step 4. Synthesis of 4-(((R)-7,8-diethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(7-((1-(4-(2,6-dioxopiperidin-3-yl)-2-fluorophenyl)piperidin-4-yl)methyl)-2,7-diazaspiro[3.5]nonan-2-yl)-3-methoxybenzamide (Compound 99)

The title compound (64.81 mg, 78.56 μmol, 33.18% yield, 98.3% purity) was obtained as a white solid by a similar method to step 6 of Example 79. MS(M+H) ⁺ =811.5.

¹ H NMR (400 MHz, DMSO- d ₆ ) δ = 10.81 (s, 1H), 9.44 (s, 1H), 8.46 (d, J = 8.4 Hz, 1H), 7.79 (s, 1H), 7.58 (s, 1H), 7.45 - 7.36 (m, 2H), 7.04 - 6.91 (m, 3H), 4.38 - 4.31 (m, 1H), 4.01 - 3.89 (m, 4H), 3.83 - 3.74 (m, 1H), 3.61 - 3.41 (m, 4H), 3.31 - 3.26 (m, 2H), 3.24 (s, 3H), 2.70 - 2.58 (m, 4H), 2.48 - 2.46 (m, 1H), 2.31 - 2.22 (m, 3H), 2.21 - 2.16 (m, 1H), 2.16 - 2.10 (m, 2H), 2.05 - 1.96 (m, 1H), 1.93 - 1.52 (m, 10H), 1.30 - 1.19 (m, 5H), 0.73 (t, J = 7.2 Hz, 3H).

Example 100. Synthesis of 4-(((R)-7,8-diethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(7-((1-(4-(2,6-dioxopiperidin-3-yl)-2-fluorophenyl)piperidin-4-yl)methyl)-7-azaspiro[3.5]nonan-2-yl)-3-methoxybenzamide (Compound 100)

Step 1. Synthesis of 1-(4-(2,6-dioxopiperidin-3-yl)-2-fluorophenyl)piperidine-4-carbaldehyde (2)

To a solution of 3-(3-fluoro-4-(4-(hydroxymethyl)piperidin-1-yl)phenyl)piperidine-2,6-dione (1 g, 3.12 mmol) in DCM (20 mL) was added DMP (1.99 g, 4.68 mmol, 1.45 mL), and the reaction mixture was stirred at 20 °C for 2 h. TLC (Petroleum ether/EtOAc=1/1) confirmed complete consumption of the starting material and the appearance of a new spot. The mixture was filtered, and the filtrate was concentrated under reduced pressure to obtain the title compound (1 g, crude) as a yellow oil.

Step 2. Synthesis of tert-butyl (7-((1-(4-(2,6-dioxopiperidin-3-yl)-2-fluorophenyl)piperidin-4-yl)methyl)-7-azaspiro[3.5]nonan-2-yl)carbamate (4)

To a solution of 1-(4-(2,6-dioxopiperidin-3-yl)-2-fluorophenyl)piperidine-4-carbaldehyde (1 g, 3.14 mmol) and tert-butyl (7-azaspiro[3.5]nonan-2-yl)carbamate (603.98 mg, 2.51 mmol) in DCM (30 mL) was added MgSO ₄ (1.13 g, 9.42 mmol) at 20 °C. After stirring for 30 min, NaBH(OAc) ₃ (998.65 mg, 4.71 mmol) was slowly added, and the reaction mixture was stirred at 20 °C for 12 h. The desired mass peak (25%) was identified by LCMS. The mixture was filtered. The filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (40 g SepaFlash® silica flash column, Eluent of 0–100% EtOAc/Petroleum ether gradient @ 80 mL/min) to give the title compound (1 g, 1.84 mmol, 58.66% yield) as a yellow solid. MS(M+H) ⁺ = 543.4.

Step 3. Synthesis of 3-(4-(4-((2-amino-7-azaspiro[3.5]nonan-7-yl)methyl)piperidin-1-yl)-3-fluorophenyl)piperidine-2,6-dione (5)

The title compound (1 g, crude, HCl salt) was obtained as a white solid by a similar method to step 3 of Example 21. MS(M+H) ⁺ = 443.3.

Step 4. Synthesis of 4-(((R)-7,8-diethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(7-((1-(4-(2,6-dioxopiperidin-3-yl)-2-fluorophenyl)piperidin-4-yl)methyl)-7-azaspiro[3.5]nonan-2-yl)-3-methoxybenzamide (Compound 100)

The title compound (149.74 mg, 162.69 μmol, 24.12% yield, 88% purity, 2TFA salt) was obtained as a white solid by a similar method to step 6 of Example 79. MS(M+H) ⁺ =810.4.

^1H NMR (400 MHz, DMSO-d ₆ ) δ = 10.83 (s, 1H), 9.29 (br s, 1H), 9.08 (br s, 1H), 8.62 (br d, J = 7.4 Hz, 1H), 8.14 (d, J = 8.8 Hz, 1H), 7.82 (s, 1H), 7.57 - 7.50 (m, 1H), 7.13 - 6.91 (m, 3H), 4.56 (t, J = 4.5 Hz, 1H), 4.45 - 4.11 (m, 1H), 4.01 - 3.87 (m, 4H), 3.81 (dd, J = 4.8, 11.8 Hz, 1H), 3.51 - 3.30 (m, 5H), 3.23 (s, 3H), 3.11 - 2.92 (m, 3H), 2.89 - 2.78 (m, 1H), 2.75 - 2.59 (m, 3H), 2.43 - 2.34 (m, 1H), 2.27 - 2.11 (m, 2H), 2.06 - 1.65 (m, 13H), 1.50 - 1.31 (m, 2H), 1.25 (t, J = 7.1 Hz, 3H), 0.76 (t, J = 7.4 Hz, 3H).

Example 101. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(7-((1-(4-(2,6-dioxopiperidin-3-yl)phenyl)-4-hydroxypiperidin-4-yl)methyl)-7-azaspiro[3.5]nonan-2-yl)-3-methoxybenzamide (Compound 101)

Step 1. Synthesis of benzyl (7-azaspiro[3.5]nonan-2-yl)carbamate (2)

To a solution of tert-butyl 2-(((benzyloxy)carbonyl)amino)-7-azaspiro[3.5]nonane-7-carboxylate (2 g, 5.34 mmol) in dioxane (5 mL) was added HCl/dioxane (2 M, 26.09 mL) at 20 °C, and the mixture was stirred at 20 °C for 2 h. The peak of the desired mass was identified by LCMS. The reaction mixture was concentrated under reduced pressure to obtain the title compound (1.6 g, crude, HCl) as a white solid. MS(M+ H) ⁺ = 275.2

Step 2. Synthesis of tert-butyl 4-((2-(((benzyloxy)carbonyl)amino)-7-azaspiro[3.5]nonan-7-yl)methyl)-4-hydroxypiperidine-1-carboxylate (4)

To a solution of benzyl (7-azaspiro[3.5]nonan-2-yl)carbamate (1.0 g, 3.22 mmol, HCl) in EtOH (20 mL) was added a solution of _tert -butyl 1-oxa-6-azaspiro[2.5]octane-6-carboxylate (1.50 g, 7.03 mmol) and K ₂ CO ₃ (1.40 g, 10.13 mmol) in H 2 O (10 mL) at 20 °C. The mixture was stirred at 100 °C under CN ₂ for 16 h. The target mass peak (71%) was identified by LCMS. The reaction mixture was concentrated under reduced pressure to remove EtOH, diluted with H ₂ O (20 mL), and extracted with EtOAc (50 mL × 2). The mixed organic layer was washed with brine (40 mL × 2), dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure. The residue was purified by prep-HPLC (column: Waters Xbridge C18 150 x 50 mm x10 μm; mobile phase: [H ₂ O (10 mM NH ₄ HCO ₃ ) -ACN]; gradient: 47% -77% B over 11.0 min; column Temp: 30 °C), and the eluate was lyophilized to obtain the title compound (1.5 g, 3.08 mmol, 95.61% yield) as a pale yellow solid. MS (M + H) ⁺ = 488.5

Step 3. Synthesis of benzyl (7-((4-hydroxypiperidin-4-yl)methyl)-7-azaspiro[3.5]nonan-2-yl)carbamate (5)

To a solution of tert-butyl 4-((2-(((benzyloxy)carbonyl)amino)-7-azaspiro[3.5]nonan-7-yl)methyl)-4-hydroxypiperidine-1-carboxylate (1.5 g, 3.08 mmol) in dioxane (20 mL) was added HCl/dioxane (2 M, 60.00 mL) at 20 °C, and the mixture was stirred at 20 °C for 2 h. The main peak of the target mass was confirmed by LCMS. The reaction mixture was concentrated under reduced pressure to obtain the title compound (1.2 g, crude) as a white solid. MS(M+H) ⁺ = 388.3

Step 4. Synthesis of benzyl (7-((1-(4-(2,6-bis(benzyloxy)pyridin-3-yl)phenyl)-4-hydroxypiperidin-4-yl)methyl)-7-azaspiro[3.5]nonan-2-yl)carbamate (7)

The title compound (900 mg, 1.20 mmol, 72.40% yield) was obtained as a yellow solid by a similar method to step 1 of Example 95. MS(M+H) ⁺ = 753.5

Step 5. Synthesis of 3-(4-(4-((2-amino-7-azaspiro[3.5]nonan-7-yl)methyl)-4-hydroxypiperidin-1-yl)phenyl)piperidine-2,6-dione (8)

To a solution of Pd/C (100 mg, 93.97 μmol, 10% purity) in CF ₃ CH ₂ OH (10 mL) was slowly added a solution of benzyl (7-((1-(4-(2,6-bis(benzyloxy)pyridin-3-yl)phenyl)-4-hydroxypiperidin-4-yl)methyl)-7-azaspiro[3.5]nonan-2-yl)carbamate (300 mg, 398.44 μmol) and TFA (153.50 mg, 1.35 mmol, 0.1 mL) in THF (5 mL) under N ₂ , and the mixture was stirred at 25 °C under CH ₂ (15 Psi) for 16 h. The peak of the target mass (33%) was identified by LCMS. The mixture was filtered and the filter cake was washed with CF ₃ CH ₂ OH (30 mL). The filtrate was concentrated under reduced pressure. The residue was purified by prep-HPLC (column: Phenomenex Luna C18 150 x 25 mm x10 μm; mobile phase: [H ₂ O (0.1% TFA) -ACN]; gradient: 0%-10% B over 15.0 min; column Temp: 30 °C), and the eluate was lyophilized to obtain the title compound (190 mg, 342.59 μmol, 85.98% yield, TFA) as a pale yellow solid. MS (M+H) ⁺ = 441.3

Step 6. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(7-((1-(4-(2,6-dioxopiperidin-3-yl)phenyl)-4-hydroxypiperidin-4-yl)methyl)-7-azaspiro[3.5]nonan-2-yl)-3-methoxybenzamide (Compound 101)

The title compound (44.3 mg, 52.05 μmol, 26.77% yield, 98% purity) was obtained as a white solid by a similar method to step 6 of Example 79. MS (M+H) ⁺ = 834.6

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.79 (s, 1H), 8.46 - 8.37 (m, 2H), 7.91 (s, 1H), 7.64 (s, 1H), 7.51 - 7.44 (m, 2H), 7.03 (d, J = 8.7 Hz, 2H), 6.89 (d, J = 8.7 Hz, 2H), 4.48 - 4.28 (m, 3H), 4.12 - 4.03 (m, 1H), 3.95 (s, 3H), 3.76 - 3.67 (m, 1H), 3.34 - 3.28 (m, 3H), 3.24 (s, 3H), 3.08 - 2.98 (m, 2H), 2.69 - 2.57 (m, 1H), 2.49 - 2.34 (m, 4H), 2.26 - 2.20 (m, 1H), 2.28 - 2.19 (m, 1H), 2.20 - 2.08 (m, 3H), 2.04 - 1.98 (m, 2H), 1.96 - 1.88 (m, 1H), 1.86 - 1.71 (m, 6H), 1.68 - 1.46 (m, 10H), 1.23 (d, J = 6.7 Hz, 3H)

Example 102. Synthesis of 4-(((R)-7,8-diethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(7-((1-(4-(2,6-dioxopiperidin-3-yl)-2-fluorophenyl)-4-hydroxypiperidin-4-yl)methyl)-7-azaspiro[3.5]nonan-2-yl)-3-methoxybenzamide (Compound 102)

The title compound (176.05 mg, 179.80 μmol, 52.53% yield, 96% purity, TFA) was obtained as a yellowish-white solid by a similar method to step 6 of Example 79. MS(M+H) ⁺ =826.5.

¹ H NMR (400 MHz, DMSO- d ₆ ) δ = 10.81 (s, 1H), 9.32 - 9.13 (m, 1H), 8.86 - 8.71 (m, 1H), 8.59 (d, J = 7.2 Hz, 1H), 8.14 (d, J = 8.8 Hz, 1H), 7.80 (s, 1H), 7.60 - 7.50 (m, 2H), 7.14 - 7.02 (m, 1H), 6.82 - 6.68 (m, 2H), 5.46 - 5.19 (m, 1H), 4.58 - 4.54 (m, 1H), 4.45 - 4.41 (m, 1H), 3.95 (s, 3H), 3.92 - 3.89 (m, 1H), 3.89 - 3.85 (m, 1H), 3.52 - 3.46 (m, 2H), 3.45 - 3.38 (m, 2H), 3.22 (s, 3H), 3.19 - 3.07 (m, 5H), 3.03 - 2.94 (m, 1H), 2.77 - 2.67 (m, 1H), 2.38 - 2.31 (m, 1H), 2.22 - 2.10 (m, 2H), 1.99 - 1.86 (m, 8H), 1.82 - 1.58 (m, 6H), 1.24 (t, J = 6.8 Hz, 3H), 0.75 (t, J = 7.6 Hz, 3H).

Example 103. Synthesis of N-(7-((1-(4-(2,6-dioxopiperidin-3-yl)-2-fluorophenyl)-4-hydroxypiperidin-4-yl)methyl)-7-azaspiro[3.5]nonan-2-yl)-4-(((R)-7-ethyl-8-isopropyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzamide (Compound 103)

Step 1. Synthesis of tert-butyl 2-(((benzyloxy)carbonyl)amino)-7-azaspiro[3.5]nonane-7-carboxylate (2)

The title compound (30.00 g, 80.11 mmol, 96.27% yield) was obtained as a white solid by a similar method to step 4 of Example 55. MS(M+H) ⁺ = 375.1.

Step 2. Synthesis of benzyl (7-azaspiro[3.5]nonan-2-yl)carbamate (3)

The title compound (10.37 g, crude, TFA) was obtained as a pale yellow oil by a similar method to step 2 of Example 52. MS(M+H) ⁺ = 275.2.

Step 3. Synthesis of tert-butyl 4-((2-(((benzyloxy)carbonyl)amino)-7-azaspiro[3.5]nonan-7-yl)methyl)-4-hydroxypiperidine-1-carboxylate (4)

To a solution of benzyl (7-azaspiro[3.5]nonan-2-yl)carbamate (10.37 g, 26.70 mmol, TFA) in dioxane (100 mL) were added DIPEA (14.84 g, 114.82 mmol) and tert-butyl 1-oxa-6-azaspiro[2.5]octane-6-carboxylate (5.00 g, 23.44 mmol). The mixture was stirred at 100 °C for 16 h. The desired mass peak (21%) was identified by LCMS. The reaction mixture was concentrated under reduced pressure, diluted with water (100 mL), extracted with EtOAc (150 mL Х 3), and the combined organic layer was washed with brine (50 mL Х 3), dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (120 g SepaFlash® silica flash column, eluent of 10–30% MeOH/EtOAc @ 80 mL/min) to give the title compound (3.00 g, 5.91 mmol, 22.12% yield, 96% purity) as a brown solid. MS(M+H) ⁺ = 488.2.

Step 4. Synthesis of benzyl (7-((4-hydroxypiperidin-4-yl)methyl)-7-azaspiro[3.5]nonan-2-yl)carbamate (5)

The title compound (1.00 g, 1.99 mmol, 33.76% yield, TFA) was obtained as a brown solid by a similar method to step 2 of Example 52. MS(M+H) ⁺ = 388.2.

Step 5. Synthesis of benzyl (7-((1-(4-(2,6-bis(benzyloxy)pyridin-3-yl)-2-fluorophenyl)-4-hydroxypiperidin-4-yl)methyl)-7-azaspiro[3.5]nonan-2-yl)carbamate (6)

The title compound (910 mg, 1.04 mmol, 54.84% yield, 88% purity) was obtained as a pale yellow oil by a similar method to step 1 of Example 95. MS(M+H) ⁺ =771.2.

Step 6. Synthesis of 3-(4-(4-((2-amino-7-azaspiro[3.5]nonan-7-yl)methyl)-4-hydroxypiperidin-1-yl)-3-fluorophenyl)piperidine-2,6-dione (7)

The title compound (130 mg, 227.04 μmol, 99.45% yield, TFA) was obtained as a pale yellow oil by a similar method to step 2 of Example 90. MS(M+H) ⁺ = 459.2.

Step 7. Synthesis of N-(7-((1-(4-(2,6-dioxopiperidin-3-yl)-2-fluorophenyl)-4-hydroxypiperidin-4-yl)methyl)-7-azaspiro[3.5]nonan-2-yl)-4-(((R)-7-ethyl-8-isopropyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzamide (Compound 103)

The title compound (101.75 mg, 100.25 μmol, 44.16% yield, 94% purity, TFA) was obtained as a yellowish-white solid by a similar method to step 6 of Example 79. MS(M+H) ⁺ =840.6.

¹ H NMR (400 MHz, DMSO- d ₆ ) δ = 10.81 (s, 1H), 9.25 - 9.11 (m, 1H), 8.84 - 8.73 (m, 1H), 8.60 (d, J = 7.2 Hz, 1H), 8.07 (d, J = 8.4 Hz, 1H), 7.81 (s, 1H), 7.60 - 7.50 (m, 2H), 7.13 - 7.03 (m, 1H), 6.80 - 6.70 (m, 2H), 5.45 - 5.16 (m, 1H), 4.50 - 4.47 (m, 1H), 4.46 - 4.40 (m, 1H), 3.93 (s, 3H), 3.90 - 3.86 (m, 1H), 3.53 - 3.47 (m, 2H), 3.42 - 3.38 (m, 2H), 3.22 (s, 3H), 3.18 - 3.05 (m, 5H), 3.01 - 2.94 (m, 1H), 2.73 - 2.66 (m, 1H), 2.37 - 2.30 (m, 1H), 2.22 - 2.10 (m, 2H), 1.99 - 1.81 (m, 8H), 1.80 - 1.61 (m, 6H), 1.35 (t, J = 6.8 Hz, 6H), 0.76 (t, J = 7.2 Hz, 3H).

Example 104. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(7-((1-(4-((2,6-dioxopiperidin-3-yl)amino)phenyl)-4-hydroxypiperidin-4-yl)methyl)-7-azaspiro[3.5]nonan-2-yl)-3-methoxybenzamide (Compound 104)

Step 1. Synthesis of benzyl (7-((4-hydroxy-1-(4-nitrophenyl)piperidin-4-yl)methyl)-7-azaspiro[3.5]nonan-2-yl)carbamate (3)

The title compound (600 mg, 1.18 mmol, 91.43% yield) was obtained as a yellow solid by a similar method to step 3 of Example 44. MS(M+H) ⁺ = 509.4

Step 2. Synthesis of benzyl (7-((1-(4-aminophenyl)-4-hydroxypiperidin-4-yl)methyl)-7-azaspiro[3.5]nonan-2-yl)carbamate (4)

The title compound (400 mg, crude) was obtained as a yellow solid by a similar method to step 4 of Example 83. MS(M+H) ⁺ = 479.3

Step 3. Synthesis of benzyl (7-((1-(4-((2,6-dioxopiperidin-3-yl)amino)phenyl)-4-hydroxypiperidin-4-yl)methyl)-7-azaspiro[3.5]nonan-2-yl)carbamate (6)

The title compound (240 mg, 406.97 μmol, 97.39% yield) was obtained as a green solid by a similar method to step 5 of Example 83. MS(M+H) ⁺ = 590.4

Step 4. Synthesis of 3-((4-(4-((2-amino-7-azaspiro[3.5]nonan-7-yl)methyl)-4-hydroxypiperidin-1-yl)phenyl)amino)piperidine-2,6-dione (7)

A solution of benzyl (7-((1-(4-((2,6-dioxopiperidin-3-yl)amino)phenyl)-4-hydroxypiperidin-4-yl)methyl)-7-azaspiro[3.5]nonan-2-yl)carbamate (120 mg, 203.49 μmol) in TFA (8.37 g, 73.43 mmol, 5.45 mL) was stirred at 50 °C under CN ₂ for 2 h. The main peak of the desired mass was confirmed by LCMS. The reaction mixture was concentrated under reduced pressure to obtain the title compound (115 mg, crude, TFA) as a green oil. MS(M+H) ⁺ = 456.3

Step 5. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(7-((1-(4-((2,6-dioxopiperidin-3-yl)amino)phenyl)-4-hydroxypiperidin-4-yl)methyl)-7-azaspiro[3.5]nonan-2-yl)-3-methoxybenzamide (Compound 104)

The title compound (35.1 mg, 40.51 μmol, 20.84% yield, 98% purity) was obtained as a white solid by a similar method to step 6 of Example 79. MS(M+H) ⁺ = 849.6

Example 105. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(2-((1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)amino)-7-azaspiro[3.5]nonan-7-yl)-3-methoxybenzamide (Compound 105)

Step 1. Synthesis of benzyl (7-azaspiro[3.5]nonan-2-yl)carbamate (2)

To a solution of tert-butyl 2-(((benzyloxy)carbonyl)amino)-7-azaspiro[3.5]nonane-7-carboxylate (2 g, 5.34 mmol) in DCM (10 mL) was added HCl/dioxane (2 M, 30 mL), and the mixture was stirred at 20 °C for 2 h. The peak of the desired mass was identified by LCMS. The mixture was concentrated under reduced pressure to obtain the title compound (1.8 g, crude, HCl salt) as a white solid.

Step 2. Synthesis of benzyl (7-nitroso-7-azaspiro[3.5]nonan-2-yl)carbamate (3)

The title compound (1.27 g, crude) was obtained as a yellow solid by a similar method to step 3 of Example 55. MS(M+H) ⁺ = 304.1

Step 3. Synthesis of benzyl tert-butyl (7-azaspiro[3.5]nonane-2,7-diyl)dicarbamate (4)

To a solution of benzyl (7-nitroso-7-azaspiro[3.5]nonan-2-yl)carbamate (1.27 g, 4.19 mmol) and NH ₄ Cl (896 mg, 16.75 mmol) in THF (12 mL) and H ₂ O (4 mL) was slowly added Zn (1.12 g, 17.13 mmol), and the mixture was stirred at 20 °C for 2 h. The peak of benzyl (7-amino-7-azaspiro[3.5]nonan-2-yl)carbamate was identified by LCMS. The mixture was filtered, and the filter cake was washed with THF (20 mL) and water (8 mL). Boc ₂ O (2.74 g, 12.56 mmol, 2.89 mL) and Na ₂ CO ₃ (2.66 g, 25.12 mmol) were added to the filtrate, and the mixture was stirred at 20 °C for 14 h. The peak of the target mass was identified by LCMS. The mixture was diluted with water (10 mL), extracted with EtOAc (30 mL x 2). The mixed organic layer was washed with water (10 mL x 2), dried over Na ₂ SO _4, and The residue was filtered. The filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (12 g SepaFlash® silica flash column, eluent of 20–30% EtOAc/Commercial hexanes gradient @ 200 mL/min) to give the title compound (520 mg, crude) as a yellow oil. MS(M+H) ⁺ = 390.2

Step 4. Synthesis of tert-butyl (2-amino-7-azaspiro[3.5]nonan-7-yl)carbamate (5)

To a solution of Pd/C (0.1 g, 10% purity) in CF ₃ CH ₂ OH (8 mL) was added a solution of benzyl tert-butyl (7-azaspiro[3.5]nonane-2,7-diyl)dicarbamate (520 mg, 1.34 mmol) in CF ₃ CH ₂ OH (8 mL) under N ₂ , and the suspension was stirred at 35 °C under CH ₂ (45 Psi) for 14 h. The peak of the desired mass was identified by LCMS. The mixture was filtered, and the filter cake was washed with EtOH (200 mL). The filtrate was concentrated under reduced pressure to give the title compound (380 mg, crude) as a yellow oil.

Step 5. Synthesis of 8-(4-(2,6-bis(benzyloxy)pyridin-3-yl)phenyl)-1,4-dioxa-8-azaspiro[4.5]decane (6B)

The title compound (930 mg, 1.83 mmol, 40.81% yield, 100% purity) was obtained as a yellow solid by a similar method to step 1 of Example 95. MS(M+H) ⁺ = 509.4

Step 6. Synthesis of 3-(4-(1,4-dioxa-8-azaspiro[4.5]decan-8-yl)phenyl)piperidine-2,6-dione (6C)

Solution 1: 8-(4-(2,6-bis(benzyloxy)pyridin-3-yl)phenyl)-1,4-dioxa-8-azaspiro[4.5]decane (930 mg, 1.83 mmol) in THF (23.25 mL). The fixed bed (named FLR1, volume 1 mL) was packed with a granular catalyst (Pd(OH) ₂ /Al ₂ O ₃ (0.73 g, 5% purity)). The H ₂ pressure regulator was adjusted to 1.5 MPa, and the H ₂ flow rate (H ₂ , 10 sccm) was set. Solution 1 was pumped by pump 1 (S ₁ , P1, 0.4 mL/min) and flowed into reactor 1 (FLR1, SS, Fixed bed, 6.350 (1/4") mm, 1.0 mL, 50.0 °C). The reaction mixture was continuously collected from the reactor into a storage vessel. The peak of the target mass was identified by LCMS. The mixture was concentrated under reduced pressure to obtain the title compound (390 mg, crude) as a white solid. MS(M+H) ⁺ = 331.2

Step 7. Synthesis of 3-(4-(4-oxopiperidin-1-yl)phenyl)piperidine-2,6-dione (6)

The title compound (290 mg, crude) as a yellow oil was obtained by a similar method to step 5 of Example 55. MS(M+H) ⁺ = 287.2

Step 8. Synthesis of tert-butyl (2-((1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)amino)-7-azaspiro[3.5]nonan-7-yl)carbamate (7)

To a solution of 3-(4-(4-oxopiperidin-1-yl)phenyl)piperidine-2,6-dione (270 mg, 942.98 μmol) and tert-butyl (2-amino-7-azaspiro[3.5]nonan-7-yl)carbamate (351 mg, 1.37 mmol) in DMAC (6 mL) was added TEA (378.04 mg, 3.74 mmol, 520 μL), and the mixture was stirred at 20 °C for 30 min. Then, NaBH ₃ CN (178 mg, 2.83 mmol) was added, and the mixture was stirred at 20 °C for 1 h. The peak of the target mass was identified by LCMS. The mixture was diluted with water (10 mL), adjusted to pH = 9 with saturated Na ₂ CO _{3 , and} the mixture was extracted with DCM (30 mL x 2). Wash the mixed organic layer with water (10 mL), dry with Na ₂ SO _{4 and} The residue was filtered. The filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (12 g SepaFlash® silica flash column, eluent of 10–20% MeOH/EtOAc gradient @ 200 mL/min) to give the title compound (170 mg, 323.39 μmol, 34.29% yield) as a yellow oil. MS(M+H) ⁺ = 526.4

Step 9. Synthesis of 3-(4-(4-((7-amino-7-azaspiro[3.5]nonan-2-yl)amino)piperidin-1-yl)phenyl)piperidine-2,6-dione (8)

The title compound (80 mg, crude, TFA salt) as a yellow oil was obtained by synthesis in a similar manner to step 2 of Example 52.

Step 10. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(2-((1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)amino)-7-azaspiro[3.5]nonan-7-yl)-3-methoxybenzamide (Compound 105)

The title compound (2.4 mg, 2.84 μmol, 1.92% yield, 97% purity) was obtained as a white solid by a similar method to step 6 of Example 79. MS(M+H) ⁺ = 819.7

^1H NMR (400 MHz, DMSO _- d6 ) δ = 10.77 (s, 1H), 9.20 (s, 1H), 8.41 (d, J = 8.8 Hz, 1H), 7.89 (s, 1H), 7.62 (s, 1H), 7.46 - 7.38 (m, 2H), 7.02 (d, J = 8.4 Hz, 2H), 6.87 (br d, J = 8.7 Hz, 2H), 4.48 - 4.38 (m, 1H), 4.32 (q, J = 6.6 Hz, 1H), 3.93 (s, 3H), 3.71 (br dd, J = 4.8, 10.8 Hz, 1H), 3.58 (br d, J = 12.1 Hz, 2H), 3.23 (s, 3H), 2.87 - 2.73 (m, 3H), 2.68 (br t, J = 11.3 Hz, 2H), 2.62 - 2.57 (m, 1H), 2.48 - 2.40 (m, 1H), 2.16 - 2.06 (m, 3H), 2.05 - 1.95 (m, 3H), 1.94 - 1.88 (m, 1H), 1.85 - 1.71 (m, 6H), 1.66 - 1.54 (m, 6H), 1.51 - 1.42 (m, 2H), 1.38 - 1.26 (m, 3H), 1.25 - 1.19 (m, 5H)

Example 106. Synthesis of 3-(4-(4-(((1r,4r)-4-(((5-(4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxyphenyl)-1,3,4-oxadiazol-2-yl)methyl)(methyl)amino)cyclohexyl)amino)methyl)piperidin-1-yl)phenyl)piperidine-2,6-dione (Compound 106)

Step 1. Synthesis of tert-butyl ((1r,4r)-4-(((5-(4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxyphenyl)-1,3,4-oxadiazol-2-yl)methyl)(methyl)amino)cyclohexyl)carbamate (3)

To a solution of (R)-2-((4-(5-(chloromethyl)-1,3,4-oxadiazol-2-yl)-2-methoxyphenyl)amino)-8-cyclopentyl-7-ethyl-5-methyl-7,8-dihydropteridin-6(5H)-one (1.1 g, 2.21 mmol) and tert-butyl ((1r,4r)-4-(methylamino)cyclohexyl)carbamate (302.62 mg, 1.33 mmol) in DMF (5 mL) were added DIPEA (570.98 mg, 4.42 mmol, 769.52 μL) and KI (36.67 mg, 220.89 μmol). The mixture was stirred at 25 °C for 12 h. LCMS confirmed 10% of (R)-2-((4-(5-(chloromethyl)-1,3,4-oxadiazol-2-yl)-2-methoxyphenyl)amino)-8-cyclopentyl-7-ethyl-5-methyl-7,8-dihydropteridin-6(5H)-one remaining and 41% of desired mass. tert-Butyl ((1r,4r)-4-(methylamino)cyclohexyl)carbamate (252.18 mg, 1.10 mmol) was added and the mixture was stirred at 25 °C for 5 h. LCMS confirmed 42% of the desired compound. The reaction mixture was diluted with H ₂ O (50 mL) and extracted with EtOAc (60 mL x 3). The mixed organic layer was washed with brine (100 mL), dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (40 g SepaFlash® silica flash column, eluent of 0–100% EtOAc/Petroleum ether gradient @ 75 mL/min) to give the title compound (590 mg, 795.40 μmol, 36.01% yield, 93% purity) as a white solid. MS(M+H) ⁺ = 690.5.

Step 2. Synthesis of (R)-2-((4-(5-(((1r,4r)-4-aminocyclohexyl)(methyl)amino)methyl)-1,3,4-oxadiazol-2-yl)-2-methoxyphenyl)amino)-8-cyclopentyl-7-ethyl-5-methyl-7,8-dihydropteridin-6(5H)-one (4)

To a solution of tert-butyl ((1r,4r)-4-(((5-(4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxyphenyl)-1,3,4-oxadiazol-2-yl)methyl)(methyl)amino)cyclohexyl)carbamate (590 mg, 855.26 μmol) in DCM (10 mL) was added HCl/dioxane (2 M, 4 mL). The mixture was stirred at 25 °C for 1 h. LCMS showed 10% of starting material remaining and 73% of desired mass. The mixture was stirred at 25 °C for 1 h. LCMS showed 81% of desired mass. The reaction mixture was filtered and the filter cake was dried under vacuum to obtain the title compound as a brown solid (480 mg, 674.55 μmol, 78.87% yield, 88% purity, HCl). MS(M+H) ⁺ =590.3.

Step 3. Synthesis of 1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidine-4-carbaldehyde (5)

The title compound (270 mg, 898.95 μmol, 33.98% yield) as a brown oil was obtained by synthesis in a similar manner to step 4 of Example 89.

Step 4. Synthesis of 3-(4-(4-(((1r,4r)-4-(((5-(4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxyphenyl)-1,3,4-oxadiazol-2-yl)methyl)(methyl)amino)cyclohexyl)amino)methyl)piperidin-1-yl)phenyl)piperidine-2,6-dione (Compound 106)

To a solution of (R)-2-((4-(5-((((1r,4r)-4-aminocyclohexyl)(methyl)amino)methyl)-1,3,4-oxadiazol-2-yl)-2-methoxyphenyl)amino)-8-cyclopentyl-7-ethyl-5-methyl-7,8-dihydropteridin-6(5H)-one (200 mg, 319.39 μmol, HCl) and 1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidine-4-carbaldehyde (95.93 mg, 319.39 μmol) in DCM (4 mL) was added TEA (96.96 mg, 958.17 μmol, 133.37 μL) and NaBH(OAc) ₃ (101.54 mg, 479.09 μmol) was added. The mixture was stirred at 25 °C for 16 h. The desired mass of 41% was confirmed by LC-MS. The reaction mixture was diluted with H ₂ O (20 mL) and extracted with DCM (15 mL x 3). The combined organic layer was washed with brine (50 mL), dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (12 g SepaFlash® silica flash column, Eluent of 0–100% EtOAc/MeOH @80 mL/min) and prep-HPLC (Column: Phenomenex luna C18 150*25 mm* 10 μm; Mobile phase: [water(TFA)-ACN]; Gradient: 9%–39% B over 12 min), and the eluate was lyophilized to obtain the title compound (71.7 mg, 70.02 μmol, 21.92% yield, 96.5% purity, TFA) as a white solid. MS(M+H) ⁺ =874.2

^1H NMR (400 MHz, DMSO- d ₆₎ δ = 10.79 (s, 1H), 8.54 - 8.34 (m, 2H), 8.27 (d, J = 8.1 Hz, 1H), 7.84 (s, 1H), 7.69 - 7.54 (m, 2H), 7.08 (d, J = 8.4 Hz, 2H), 6.97 (d, J = 8.3 Hz, 2H), 4.78 - 4.67 (m, 2H), 4.43 - 4.40 (m, 1H), 4.28 - 4.20 (m, 1H), 3.98 (s, 3H), 3.76 - 3.69 (m, 3H), 3.30 - 3.20 (m, 4H), 3.10 - 3.00 (m, 1H), 2.98 - 2.88 (m, 2H), 2.87 - 2.58 (m, 6H), 2.47 - 2.40 (m, 1H), 2.25 - 2.07 (m, 5H), 2.05 - 1.90 (m, 3H), 1.89 - 1.70 (m, 7H), 1.67 - 1.46 (m, 6H), 1.45 - 1.27 (m, 4H), 0.76 (t, J = 7.4 Hz, 3H)

Example 107. Synthesis of 3-(4-(4-(((1r,4r)-4-((5-(4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxyphenyl)-1,3,4-oxadiazol-2-yl)amino)cyclohexyl)amino)methyl)piperidin-1-yl)phenyl)piperidine-2,6-dione (Compound 107)

Step 1. Synthesis of tert-butyl (R)-2-(4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoyl)hydrazine-1-carboxylate (3)

To a solution of (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoic acid (2 g, 4.70 mmol) and HATU (2.14 g, 5.64 mmol) in DMF (40 mL) was added DIPEA (1.82 g, 14.10 mmol, 2.46 mL), and the mixture was stirred at 15 °C for 15 min. tert-Butyl hydrazinecarboxylate (1.24 g, 9.40 mmol) was added, and the mixture was stirred at 15 °C for 14 h. The desired mass peak (94%) was confirmed by LCMS. The mixture was diluted with brine (60 mL) and extracted with EtOAc (30 mL x 3), and the combined organic layers were washed with brine (50 mL x 2), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure and purified by flash silica gel chromatography (12 g SepaFlash® silica flash column, Eluent of 60–100% EtOAc/Petroleum ether to 10% MeOH/EtOAc gradient @ 100 mL/min) to afford the title compound (2.85 g, 4.65 mmol, 98.87% yield, 88% purity) as a yellow oil. MS(M+H) ⁺ =540.4.

Step 2. Synthesis of (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzohydrazide (4)

The title compound (2.5 g, crude, HCl salt) was obtained as a yellow solid by a similar method to step 2 of Example 106. MS(M+H) ⁺ = 440.3.

Step 3. Synthesis of tert-butyl ((1r,4r)-4-((5-(4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxyphenyl)-1,3,4-oxadiazol-2-yl)amino)cyclohexyl)carbamate (7)

To a solution of tert-butyl ((1r,4r)-4-aminocyclohexyl)carbamate (1.00 g, 4.67 mmol) in DMF (20 mL) was added di(1H-imidazol-1-yl)methanethione (832 mg, 4.67 mmol), and the mixture was stirred at 15 °C for 14 h. A solution of (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzohydrazide (1.11 g, 2.33 mmol, HCl salt) and TEA (1.42 g, 14.00 mmol, 1.95 mL) in DMF (20 mL) was added, and the mixture was stirred at 15 °C for 14 h. The peak (79%) of tert-butyl ((1r,4r)-4-(2-(4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoyl)hydrazine-1-carbothioamido)cyclohexyl)carbamate was identified by LCMS. EDCI (1.34 g, 7.00 mmol) was added and the mixture was stirred at 80 °C for 2 h. The mixture was diluted with brine (100 mL) and extracted with EtOAc (30 mL x 3). The combined organic layer was washed with brine (50 mL x 2), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (12 g SepaFlash® silica flash column, eluent of 0–10% MeOH/EtOAc gradient @ 100 mL/min) to give the title compound (1.3 g, 1.89 mmol, 40.41% yield, 96% purity) as a yellow solid. MS(M+H) ⁺ =662.5.

SFC Method Com :Column: Chiralcel OD-3 50Х4.6 mm ID , 3um; Mobile phase: Phase A for CO ₂ , and Phase B for EtOH (0.05%DEA); Gradient elution: 40%B in A; Flow rate: 3mL/min; Detector:DAD; Column Temp: 35C; Back Pressure: 100Bar.

Step 4. Synthesis of (R)-2-((4-(5-(((1r,4r)-4-aminocyclohexyl)amino)-1,3,4-oxadiazol-2-yl)-2-methoxyphenyl)amino)-8-cyclopentyl-7-ethyl-5-methyl-7,8-dihydropteridin-6(5H)-one (8)

The title compound (1.2 g, crude, HCl salt) was obtained as a yellow solid by a similar method to step 2 of Example 106. MS(M+H) ⁺ =562.4.

Step 5. Synthesis of 3-(4-(4-(((1r,4r)-4-((5-(4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxyphenyl)-1,3,4-oxadiazol-2-yl)amino)cyclohexyl)amino)methyl)piperidin-1-yl)phenyl)piperidine-2,6-dione (Compound 107)

The title compound (358.52 mg, 354.77 μmol, 17.68% yield, 95% purity, TFA salt) was obtained as a white solid by a similar method to step 5 of Example 89. MS(M+H) ⁺ =846.5.

SFC Method details: "Column: Chiralpak AD-3 50Х4.6mm ID, 3um Mobile phase: Phase A for CO ₂ , and Phase B for IPA+ACN (0.05%DEA); Gradient elution: 60% IPA+ACN (0.05% DEA) in CO ₂ Flow rate: 3mL/min; Detector: PDA column Temp: 35C; Back Pressure: 100Bar"

¹ H NMR (400 MHz, DMSO- d ₆ ) δ = 10.79 (s, 1H), 8.45 - 8.30 (m, 2H), 8.00 - 7.82 (m, 2H), 7.77 (s, 1H), 7.48 - 7.38 (m, 2H), 7.16 - 7.05 (m, 2H), 7.04 - 6.95 (m, 2H), 4.50 - 4.40 (m, 1H), 4.20 - 4.08 (m, 1H), 3.92 (s, 3H), 3.79 - 3.66 (m, 3H), 3.48 - 3.35 (m, 1H), 3.23 (s, 3H), 3.13 - 3.02 (m, 1H), 2.97 - 2.87 (m, 2H), 2.83 - 2.70 (m, 1H), 2.69 - 2.59 (m, 1H), 2.21 - 2.06 (m, 5H), 2.04 - 1.72 (m, 11H), 1.55 - 1.27 (m, 11H), 0.75 (br t, J = 7.4 Hz, 3H)

Example 108. Synthesis of 3-(4-(4-(((1r,4r)-4-(((5-(4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxyphenyl)-1,3,4-oxadiazol-2-yl)methyl)amino)cyclohexyl)(methyl)amino)methyl)piperidin-1-yl)phenyl)piperidine-2,6-dione (Compound 108)

Step 1. Synthesis of 1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidine-4-carbaldehyde (2)

The title compound (210 mg, 699.18 μmol, 26.43% yield) was obtained as a white solid by a similar method to step 4 of Example 89. MS(M+H) ⁺ = 301.2.

^1H NMR (400 MHz, DMSO _- d6 ) δ = 10.76 (s, 1H), 9.63 (s, 1H), 7.04 (d, J = 8.6 Hz, 2H), 6.90 (d, J = 8.8 Hz, 2H), 3.72 (dd, J = 4.8, 10.9 Hz, 1H), 3.60 - 3.50 (m, 2H), 2.87 - 2.73 (m, 2H), 2.69 - 2.59 (m, 1H), 2.48 - 2.41 (m, 2H), 2.18 - 2.08 (m, 1H), 2.04 - 1.98 (m, 1H), 1.97 - 1.86 (m, 2H), 1.64 - 1.50 (m, 2H)

Step 2. Synthesis of tert-butyl ((1r,4r)-4-(((1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)methyl)(methyl)amino)cyclohexyl)carbamate (4)

The title compound (460 mg, crude) was obtained as a white solid by a similar method to step 1 of Example 68. MS(M+H) ⁺ =513.5.

Step 3. Synthesis of 3-(4-(4-(((1r,4r)-4-aminocyclohexyl)(methyl)amino)methyl)piperidin-1-yl)phenyl)piperidine-2,6-dione (5)

The title compound (500 mg, crude, HCl) was obtained as a white solid by a similar method to step 3 of Example 21. MS(M+H) ⁺ = 413.5.

Step 4. Synthesis of tert-butyl (R)-2-(4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoyl)hydrazine-1-carboxylate (9)

The title compound (920 mg, 1.60 mmol, 68.19% yield, 94% purity) was obtained as a white solid by a similar method to step 1 of Example 107. MS(M+H) ⁺ =540.3.

Step 5. Synthesis of (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzohydrazide (10)

To a solution of tert-butyl (R)-2-(4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoyl)hydrazine-1-carboxylate (920 mg, 1.70 mmol) in DCM (6 mL) was added TFA (4.61 g, 40.39 mmol, 3 mL). The mixture was stirred at 25 °C for 3 h. LCMS confirmed the complete consumption of tert-butyl (R)-2-(4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoyl)hydrazine-1-carboxylate. The reaction mixture was concentrated under reduced pressure to obtain the title compound (2.4 g, crude, TFA) as a brown oil. MS(M+H) ⁺ =440.3.

Step 6. Synthesis of (R)-N'-(2-chloroacetyl)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzohydrazide (11)

To a solution of (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzohydrazide (2.4 g, 4.34 mmol, TFA) in DCM (40 mL) were added DIPEA (2.23 g, 17.22 mmol, 3.00 mL) and 2-chloroacetyl chloride (170.16 mg, 1.51 mmol, 120.00 μL) at 0 °C. The mixture was stirred at 20 °C for 13.5 h. LCMS revealed 28% of starting material remaining and 47% of desired mass. 2-Chloroacetyl chloride (17.02 mg, 150.66 μmol, 12 μL) was added and the mixture was stirred at 20 °C for 2 h. LC-MS confirmed 5% of starting material remaining and 75% of the desired mass. 2-Chloroacetyl chloride (85.08 mg, 753.30 μmol, 60.00 μL) was added and stirred at 20 °C for 1.5 h. LCMS confirmed 76% of the desired mass. The reaction mixture was filtered, the filtrate was diluted with H ₂ O (40 mL), the mixture was extracted with DCM (60 mL x 2), the combined organic layers were washed with brine (80 mL x 1), dried over Na ₂ SO ₄ , filtered, and the filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (12 g SepaFlash® silica flash column, Eluent of 0–100% EtOAc/Petroleum ether gradient @ 40 mL/min) to give the title compound (600 mg, 1.00 mmol, 23.06% yield, 86% purity) as a white solid. MS(M+H) ⁺ = 516.3.

Step 7. Synthesis of (R)-2-((4-(5-(chloromethyl)-1,3,4-oxadiazol-2-yl)-2-methoxyphenyl)amino)-8-cyclopentyl-7-ethyl-5-methyl-7,8-dihydropteridin-6(5H)-one (6)

Tol. (3 mL) A solution of (R)-N'-(2-chloroacetyl)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzohydrazide (600 mg, 1.00 mmol) and POCl ₃ (4.94 g, 32.19 mmol, 3 mL) was degassed and purged three times under N ₂ , and the mixture was stirred at 90 °C under CN ₂ for 16 h. The desired mass of 79% was confirmed by LCMS. The reaction mixture was concentrated under reduced pressure to remove POCl ₃ . The product was then diluted with DCM (30 mL), the organic layer was washed with NaHCO ₃ (30 mL x 2), dried over Na ₂ SO ₄ , filtered and concentrated under reduced pressure to obtain the title compound (348 mg, 594.00 μmol, 59.40% yield, 85% purity) as a brown solid. MS(M+H) ⁺ =498.1.

Step 8. Synthesis of 3-(4-(4-(((1r,4r)-4-(((5-(4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxyphenyl)-1,3,4-oxadiazol-2-yl)methyl)amino)cyclohexyl)(methyl)amino)methyl)piperidin-1-yl)phenyl)piperidine-2,6-dione (Compound 108)

To a solution of 3-(4-(4-((((1r,4r)-4-aminocyclohexyl)(methyl)amino)methyl)piperidin-1-yl)phenyl)piperidine-2,6-dione (430 mg, 957.62 μmol, HCl) and (R)-2-((4-(5-(chloromethyl)-1,3,4-oxadiazol-2-yl)-2-methoxyphenyl)amino)-8-cyclopentyl-7-ethyl-5-methyl-7,8-dihydropteridin-6(5H)-one (330 mg, 662.68 μmol) in DMF (2 mL) were added DIPEA (371.30 mg, 2.87 mmol, 500.40 μL) and KI (15.90 mg, 95.76 μmol). The mixture was stirred at 60 °C for 21.5 h. The desired mass was confirmed as 37% by LCMS. The reaction mixture was diluted with H ₂ O (20 mL) and extracted with EtOAc (20 mL x 3). The combined organic layers were washed with brine (50 mL x 2), dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (20 g SepaFlash® silica flash column, Eluent of 0–10% DCM/MeOH @ 45 mL/min) and repurified by reversed-phase HPLC (Column: Phenomenex luna C18 250*50 mm*15 um; Mobile phase: [water (TFA) -ACN]; Gradient: 8%-38% B over 10 min). The extract was then lyophilized to obtain the title compound as a white solid (130.1 mg, 102.70 μmol, 10.72% yield, 96% purity, 3TFA). MS(M+H) ⁺ =874.5.

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.79 (s, 1H), 9.94 - 9.76 (m, 1H), 9.11 - 8.87 (m, 1H), 8.33 - 8.21 (m, 1H), 7.86 (s, 1H), 7.67 - 7.56 (m, 2H), 7.08 (d, J = 8.6 Hz, 2H), 6.96 (d, J = 8.4 Hz, 2H), 4.74 (s, 2H), 4.41 (dd, J = 3.2, 6.5 Hz, 1H), 4.27 (t, J = 8.7 Hz, 1H), 3.98 (s, 3H), 3.79 - 3.66 (m, 3H), 3.35 - 3.20 (m, 4H), 3.18 - 3.07 (m, 1H), 3.01 - 2.87 (m, 1H), 2.83 - 2.73 (m, 4H), 2.70 - 2.59 (m, 1H), 2.45 (d, J) = 4.8 Hz, 2H), 2.33 - 2.23 (m, 2H), 2.20 - 2.06 (m, 3H), 2.05 - 1.69 (m, 10H), 1.68 - 1.44 (m, 8H), 1.42 - 1.18 (m, 3H), 0.77 (t, J) = 7.5 Hz, 3H)

Example 109. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(1-(1-(6-(2,6-dioxopiperidin-3-yl)pyridin-3-yl)azetidin-3-yl)piperidin-4-yl)-3-methoxybenzamide (Compound 109)

Step 1. Synthesis of benzyl 3-(4-((tert-butoxycarbonyl)amino)piperidin-1-yl)azetidine-1-carboxylate (3)

To a solution of benzyl 3-oxoazetidine-1-carboxylate (5 g, 24.37 mmol) and tert-butyl piperidin-4-ylcarbamate (4.67 g, 23.30 mmol) in MeOH (100 mL) was added AcOH (1.38 g, 23.02 mmol, 1.32 mL), and the mixture was stirred at 20 °C for 30 min. NaBH ₃ CN (2.19 g, 34.81 mmol) was slowly added at 0 °C, and the mixture was stirred at 20 °C for 14 h. The desired mass peak at 79% was confirmed by LCMS. The mixture was diluted with NaHCO ₃ (100 mL) and extracted with EtOAc (50 mL x 3), the combined organic phases were washed with NaHCO ₃ (20 mL x 2), dried over Na ₂ SO ₄ , and filtered. The filtrate was concentrated under reduced pressure and purified by flash silica gel chromatography (40 g SepaFlash® silica flash column, Eluent of 50–100% EtOAc/Petroleum ether gradient @ 100 mL/min) to afford the title compound (6.44 g, 16.53 mmol, 71.25% yield, 100% purity) as a yellow oil. MS(M+H) ⁺ = 390.3.

Step 2. Synthesis of tert-butyl (1-(azetidin-3-yl)piperidin-4-yl)carbamate (4)

To a solution of Pd/C (1 g, 10% purity) in EtOH (20 mL) was added a solution of benzyl 3-(4-((tert-butoxycarbonyl)amino)piperidin-1-yl)azetidine-1-carboxylate (6.44 g, 15.12 mmol, HCl) in ethanol (80 mL) under N ₂ , followed by slow addition of HCl (1 M, 7.56 mL) under N ₂ , and the mixture was stirred at 40 °C ( ₁₅ Psi) for 24 h. LCMS confirmed that 65% of the starting material remained. To a solution of Pd/C (1 g, 10% purity) in EtOH (10 mL) was added the mixture under N ₂ , and the mixture was stirred at ₄₀ °C (15 Psi) for 14 h. LCMS confirmed that the starting material was consumed and the desired mass. The mixture was filtered, the filter cake was washed with THF (100 mL) and EtOH (200 mL), and the filtrate was concentrated under reduced pressure to obtain the title compound (3.6 g, crude, HCl) as a white solid. MS(M+H) ⁺ =256.3.

Step 3. Synthesis of tert-butyl (1-(1-(6-bromopyridin-3-yl)azetidin-3-yl)piperidin-4-yl)carbamate (6)

To a solution of tert-butyl (1-(azetidin-3-yl)piperidin-4-yl)carbamate (1.8 g, 6.17 mmol, HCl) and 2-bromo-5-iodopyridine (2.10 g, 7.40 mmol) in dioxane (50 mL) were added t-BuONa (1.48 g, 15.42 mmol), Pd ₂ (dba) ₃ (112.97 mg, 123.37 μmol), and XantPhos (107.07 mg, 185.05 μmol), and the mixture was stirred at 80 °C under CN ₂ for 14 h. The desired mass peak was identified by LCMS. The mixture was filtered, and the filter cake was washed with EtOAc (100 mL). The filtrate was concentrated under reduced pressure and purified by flash silica gel chromatography (12 g SepaFlash® silica flash column, eluent of 50–100% EtOAc/Petroleum ether gradient @ 100 mL/min). The product was diluted with MTBE (30 mL), and the mixture was stirred at 25 °C for 15 min. The mixture was filtered, and the filter cake was washed with MTBE (5 mL). The filter cake was collected and concentrated under reduced pressure to give the title compound (1.42 g, 3.38 mmol, 54.85% yield, 98% purity) as a white solid. MS(M+H) ⁺ = 411.2

Step 4. Synthesis of tert-butyl (1-(1-(2',6'-bis(benzyloxy)-[2,3'-bipyridin]-5-yl)azetidin-3-yl)piperidin-4-yl)carbamate (8)

The title compound (1.38 g, 2.22 mmol, 64.29% yield, 100% purity) was obtained as a yellow solid by a similar method to step 1 of Example 21. MS(M+H) ⁺ = 622.4

Step 5. Synthesis of tert-butyl (1-(1-(6-(2,6-dioxopiperidin-3-yl)pyridin-3-yl)azetidin-3-yl)piperidin-4-yl)carbamate (9)

The title compound (510 mg, 1.14 mmol, 51.29% yield, 99% purity) was obtained as a gray solid by a similar method to step 3 of Example 89. MS(M+H) ⁺ = 444.3.

Step 6. Synthesis of 3-(5-(3-(4-aminopiperidin-1-yl)azetidin-1-yl)pyridin-2-yl)piperidine-2,6-dione (10)

The title compound (520 mg, crude, TFA) was obtained as a yellow oil by a similar method to step 2 of Example 32. MS(M+H) ⁺ = 344.3

Step 7. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(1-(1-(6-(2,6-dioxopiperidin-3-yl)pyridin-3-yl)azetidin-3-yl)piperidin-4-yl)-3-methoxybenzamide (Compound 109)

The title compound (424.7 mg, 537.32 μmol, 50.80% yield, 95% purity) was obtained as a white solid by a similar method to step 6 of Example 79. MS(M+H) ⁺ = 751.5

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.75 (s, 1H), 8.40 (d, J = 8.9 Hz, 1H), 8.09 (d, J = 7.5 Hz, 1H), 7.83 (s, 1H), 7.75 - 7.72 (m, 1H), 7.59 (s, 1H), 7.49 - 7.44 (m, 2H), 7.13 (d, J = 8.4 Hz, 1H), 6.85 - 6.80 (m, 1H), 4.35 (t, J = 7.9 Hz, 1H), 4.22 (dd, J = 3.3, 7.4 Hz, 1H), 3.97 (t, J = 7.1 Hz, 2H), 3.93 (s, 3H), 3.85 (dd, J = 5.4, 8.8 Hz, 1H), 3.81 - 3.73 (m, 1H), 3.65 - 3.59 (m, 2H), 3.23 (s, 3H), 2.86 - 2.79 (m, 2H), 2.60 - 2.53 (m, 2H), 2.24 - 1.71 (m, 14H), 1.67 - 1.49 (m, 5H), 0.75 (t, J = 7.4 Hz, 3H).

Example 110. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)piperidin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 110)

Step 1. Synthesis of tert-butyl ((1r,4r)-4-(4-oxopiperidin-1-yl)cyclohexyl)carbamate (3)

To a solution of tert-butyl ((1r,4r)-4-aminocyclohexyl)carbamate (2 g, 9.33 mmol) in MeOH (20 mL) were added 1,5-dichloropentan-3-one (2.89 g, 18.67 mmol) and NaHCO ₃ (3.92 g, 46.66 mmol, 1.82 mL) at 20 °C, and the resulting mixture was stirred at 65 °C for 12 h. The reaction mixture was diluted with H ₂ O (60 mL) and extracted with EtOAc (30 mL x 3). The organic layer was dried over Na ₂ SO ₄ , filtered, and concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (120 g SepaFlash® silica flash column, eluent of 50–100 % EtOAc/Petroleum ether gradient @ 200 mL/min) to give the title compound (1.59 g, 5.36 mmol, 57.48% yield) as an orange solid. MS(M+H) ⁺ = 297.2

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 6.69 (br d, J = 7.6 Hz, 1H), 3.22 - 3.07 (m, 1H), 2.75 (t, J = 5.9 Hz, 4H), 2.45 - 2.35 (m, 1H), 2.29 (t, J = 5.8 Hz, 4H), 1.78 (br t, J = 13.9 Hz, 4H), 1.37 (s, 9H), 1.33 - 1.22 (m, 2H), 1.21 - 1.09 (m, 2H)

Step 2. Synthesis of tert-butyl ((1r,4r)-4-(4-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)piperidin-1-yl)cyclohexyl)carbamate (5)

The title compound (361 mg, 603.02 μmol, 59.58% yield, TFA salt) was obtained as a white solid by a similar method to step 1 of Example 50. MS(M+H) ⁺ = 485.3

Step 3. Synthesis of 3-(4-((1-((1r,4r)-4-aminocyclohexyl)piperidin-4-yl)amino)phenyl)piperidine-2,6-dione (6)

The title compound (255 mg, crude, HCl salt) was obtained as a white solid by a similar method to step 4 of Example 60. MS(M+H) ⁺ = 385.2

Step 4. Synthesis of 4-(((R)-8-cyclopentyl-5,7-dimethyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)piperidin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 110)

The title compound (57 mg, 71.07 μmol, 29.24% yield, 97% purity) was obtained as a white solid by a similar method to step 6 of Example 39. MS(M+H) ⁺ = 778.5

^1H NMR (400 MHz, DMSO- d ₆ ) δ = 10.73 (s, 1H), 8.41 (d, J = 8.8 Hz, 1H), 8.03 (br d, J = 7.9 Hz, 1H), 7.90 (s, 1H), 7.62 (s, 1H), 7.52 - 7.41 (m, 2H), 6.88 (d, J = 8.4 Hz, 2H), 6.52 (d, J = 8.6 Hz, 2H), 5.35 (br d, J = 7.9 Hz, 1H), 4.48 - 4.37 (m, 1H), 4.32 (q, J = 6.8 Hz, 1H), 3.94 (s, 3H), 3.78 - 3.66 (m, 1H), 3.62 (dd, J = 5.0, 10.5 Hz, 1H), 3.23 (s, 3H), 3.17 - 3.08 (m, 1H), 2.86 - 2.75 (m, 2H), 2.66 - 2.55 (m, 1H), 2.45 - 2.41 (m, 1H), 2.30 (br t, J = 10.2 Hz, 3H), 2.14 - 2.05 (m, 1H), 2.04 - 1.97 (m, 2H), 1.96 - 1.88 (m, 4H), 1.83 - 1.77 (m, 4H), 1.64 - 1.54 (m, 2H), 1.44 - 1.30 (m, 6H), 1.23 (d, J = 6.7 Hz, 3H), 1.18 - 1.08 (m, 2H), 0.88 - 0.75 (m, 1H)

Synthesis of Examples 111 to 131 (Compounds 111 to 131).

Compounds 111 to 131 were synthesized with reference to the descriptions of Examples 1 to 110 described above.

<Experimental Example>

The following compounds were selected as comparative examples to compare the cancer cell line killing effect of the compounds according to the present invention. Comparative Example 1 is a compound designated as HBL-4 in the literature [Mu, Xupeng, et al. Biochemical and biophysical research communications 521.4 (2020): 833-839.], and Comparative Example 2 is a compound designated as compound no. 11 in International Patent Publication No. WO2023/277583.

[Comparative Example 1]

[Comparative Example 2]

Experimental Example 1. Measurement of PLK1 resolution using a luciferase assay.

Generation and culture of HeLa LgBit (Plk1-HiBit KI) cell line

HeLa cells were transfected with the LgBit vector to generate a stable expression cell line. Next, gRNA and donor vectors were constructed to express the HiBit amino acid sequence behind the C-terminus of the Plk1 gene present in each cell, and then inserted into the cells along with a vector capable of expressing CRISPR/Cas9. Only cells that had undergone complete insertion and knock-in were selected and passaged for use.

For cell counting, a Thermo cell counter (Catalog # AMQAX1000) and 0.4% trypan blue solution were used.

For cell culture, DMEM (Gibco, Cat. No. 11995-065; Lot. No. 2994601), FBS (Gibco, Cat. No. 16000-044; Lot. No. U2781540P), penicillin/streptomycin (PS) (Gibco, Cat. No. 15140-122; Lot. No. 227766), 100 ㎟ cell culture dish (SPL, Cat. No. 20100), 150 ㎟ cell culture dish (SPL, Cat. No. 20150), 96-well white plate (SPL, Cat. No. 30196), PBS pH7.4 (Gibco, Cat. No. 10010-023; Lot. No. 2662269), TrypLE ^TM Express (Gibco, Cat. No. 12605-010; Lot. No. 12605-010), counting chamber (Hematocytometer) (Hirschmann, Cat. No. 8100204), and 0.4% trypan blue solution (DYNEBIO, Cat. No. CBT3710; Lot. No. 20240731) were used.

Compound treatment and luciferase assay experimental method of the present invention

The example compound was completely dissolved in DMSO (Sigma-Aldrich Cat. No. D2438, Lot. No. RNBM8168) and used in the experiment.

For HeLa LgBit (Plk1-HiBit KI), compound treatment was performed after thymidine block followed by release, and the process is as follows. Thymidine (Sigma-Aldrich Cat. No. T9250-5G) was completely dissolved in DW and used in the experiment. For thymidine block, 2 mM thymidine was treated and incubated for 24 hours. For release and chemical treatment, the medium was suctioned and washed with 1× PBS. TyppLE ^TM was added and incubated for 5 minutes in a 37°C _CO2 incubator. Neutralized cells were counted using a counter by adding complete media. 3.3 x ¹⁰⁴ cells were seeded in each well of a 96-well white plate, and the total medium volume was 150 μl, and then incubated in a _CO2 incubator.

After incubating the cell line in a _CO2 incubator for 18 hours, Eudurazine (Promega, Cat. No. N257B; Lot. No. 0000552321) was added to each well to make up 4% of the total volume. After treating to a concentration of each compound of 300 nM or 30 nM, the wavelength of the plate reader (BMG Labtech, CLARIOSTAR) was set to 470-480 nM, and luminescence was tracked in real time. After 9 hours, the luminescence value was obtained and displayed as a bar graph using Excel.

The activity was displayed in Table 2 (when treated with a compound concentration of 300 nM) and Table 3 (when treated with a compound concentration of 30 nM) according to the fluorescence value ratio of each example compound treatment group and DMSO treatment group (++++: 0.2 or less, +++: 0.2 to 0.3, ++: 0.3 to 0.5, +: 0.5 to 0.7).

[Table 2]

[Table 3]

2. Measurement of cell line killing effect

Cell line culture

Cell lines derived from lung cancer, NCI-H526 (hereinafter H526) and NCI-H69 (hereinafter H69), as well as chronic myelogenous leukemia (K562), Hodgkin lymphoma (L540), acute monocytic leukemia (THP-1), anaplastic large cell lymphoma (Karpas 299), breast cancer (MCF-7, MDA-MB-468, SK-BR-3), ovarian cancer (SKOV-3), gastric cancer (N87), non-small cell lung cancer (Calu-6), and multiple myeloma (MM1.S) were obtained from the Korea Cell Line Bank.

For cell culture, RPMI medium 1640 (Gibco, Cat. No. 22400-089; Lot. No. 292503), FBS (Gibco, Cat. No. 16000-044; Lot. No. U3109271P), penicillin/streptomycin (PS) (Gibco, Cat. No. 15140-122; Lot. No. 227766) were mixed and used, and 75T cell culture flask (SPL, Cat. No. 71075), 175T cell culture flask (SPL, Cat. No. 71175), 96-well cell culture plate (SPL, Cat. No. 30096), cell counter (Hematocytometer) (AS one, Cat. No. 4-458-01), and 0.4% trypan were used. Blue solution (DYNEBIO, Cat. No. CBT3710; Lot. No. 20240731) was used.

Treatment of the compound of the present invention

Comparative and example compounds were completely dissolved in DMSO (Sigma-Aldrich Cat. No. D2438, Lot. No. RNBM8186) and used in the experiment.

Each cell line was seeded in a 96-well cell culture plate at 7 x 10 ⁴ and 3 x 10 ⁴ cells per well, respectively, and the medium volume of each well was adjusted to 150 ㎕.

The intracellular treatment capacity of the compound of the present invention varied for each example compound, and treatment was performed at each concentration by diluting the maximum concentration by 1/3. After treating the compound so that the total solution volume in each well was 200 μl, the cells were cultured in a _CO2 incubator (Thermo Fisher Science, Cat. No. 4111) for 5 days.

Cytotoxicity test

After incubation, 20 ㎕ of EZ-Cytox (DOGEN, Cat. NO. EZ-3000, Lot. No. DLS2408) was added to each well of a 96-well plate, and incubated for 4 hours in an incubator at 37℃ and ₅ % CO2. After incubation, the absorbance of the sample was measured using a plate reader (BMG Labtech, CLARIOstar Plus) with a wavelength set to 450 nM, and the sample was shaken for 3 minutes in the plate reader before measurement. The final measurement values were organized into an Excel file, and a graph was displayed using the Prism-GraphPad program (ver. 9), and the IC ₅₀ value was measured.

The IC ₅₀ values indicating the cytotoxic effect on each cell line were graded and shown in Tables 4 and 5 below (+++++: 1 nM or less, ++++: 1 to 5 nM, +++: 5 to 10 nM, ++: 10 to 20 nM, +: 20 to 30 nM)

[Table 4]

[Table 5]

Meanwhile, the cell line killing effect of Comparative Example Compound 1 was measured on the same cell line, and the following cytotoxic effect values (IC ₅₀ values) were obtained.

[Table 6]

Claims (7)

A compound represented by the following chemical formula I: [Chemical Formula I] In the above chemical formula I, R ₁ is methyl, ethyl, isopropyl or cyclopentyl; R ₂ is methyl or ethyl; R ₃ is CH, CF, COCH ₃ or N; R ₄ is H, F, OH, CH ₃ , OCH ₃ , OCH ₂ CH ₂ OH, OCH(CH ₃ ) ₂ OC(CH3) ₃ or O-cyclopentyl; ULM is a moiety represented by the following chemical formula II-1 or II-2 {wherein, within the moiety represents a covalent bond connecting to L ₁ }, [Chemical Formula II-1] {In the above chemical formula II-1, U ₁ is a single bond, -NH-, -O- or -N(CH ₃ )-; U ₂ is CH, CD or N [wherein D is deuterium]; U ₃ and U ₄ are each independently CH or N; U ₅ and U ₆ are each independently H, F, CH ₃ , OH or OCH ₃ . [Chemical Formula II-2] {In the above chemical formula II-2, U ₇ is CH or N} L ₁ is a single bond, NH, NHCH ₂ , NHCH ₂ CH ₂ , NHCO or NCO; L ₂ and L ₄ are each independently cyclohexyl, piperidinyl, piperazinyl, cyclobutyl, azetidinyl, 7-azaspiro[3.5]nonyl, 2,7-diazaspiro[3.5]nonyl, hydroxypiperidinyl, 2-azaspiro[3.3]heptane, spiro[3.3]heptane, 2-azaspiro[3.3]heptane, 2-azaspiro[3.3]heptane, pyrrolidine and; L ₃ is a single bond, CH ₂ , NH, N(CH ₃ ), CH ₂ CH ₂ , CH ₂ NH, CH ₂ N(CH ₃ ), NHCH2, N(CH ₃ )CH ₂ or CH ₂ CH ₂ C(=O); L ₅ is , , or {Here, within the above L ₅ represents a covalent bond connecting to L ₄ }. [Amendment pursuant to Rule 26 of the Rules 04.06.2025]
In the first paragraph, ULM is a compound selected from the group consisting of the following moieties:

In the first paragraph, a compound wherein L ₂ is selected from the group consisting of the following moieties: In the first paragraph, a compound wherein L ₄ is selected from the group consisting of the following moieties: In the first paragraph, the compound represented by the chemical formula I is a compound selected from the group consisting of the following compounds: A compound according to any one of claims 1 to 5, which induces PLK1 (polo-like kinase) 1 protein degradation. A compound according to any one of claims 1 to 5, wherein the compound is conjugated to an antibody.