WO2024116069A1

WO2024116069A1 - Novel trilaciclib intermediates, method of preparation and use thereof

Info

Publication number: WO2024116069A1
Application number: PCT/IB2023/061979
Authority: WO
Inventors: Rushikesh Vilasrao KADU; Vadivelanv RENGASAMY; Satnam Singh; Subramanya Sharma; Vaibhav Suresh DAUND; Sandeep Kushwaha; Kanhaiya Lal; Venkata Subbarao YAZALI
Original assignee: Assia Chemical Industries Ltd
Current assignee: Assia Chemical Industries Ltd
Priority date: 2022-11-28
Filing date: 2023-11-28
Publication date: 2024-06-06
Anticipated expiration: 2025-05-28
Also published as: EP4626866A1

Abstract

Aspects of the present disclosure provide novel intermediates that may be used for synthesis of Trilaciclib, pharmaceutically acceptable salts or derivatives thereof. Aspects of the present disclosure also relate to a method for preparation of Trilaciclib intermediates. Further aspects of the present disclosure relate to method for preparation of Trilaciclib, pharmaceutically acceptable salts and derivatives thereof. Still further aspects of the present disclosure are drawn towards use of the Trilaciclib intermediates for the production of Trilaciclib, pharmaceutically acceptable salts or derivatives thereof.

Description

NOVEL TRILACICLIB INTERMEDIATES, METHOD OF PREPARATION AND USE THEREOF

TECHNICAL FIELD

[0001] Aspects of the present disclosure provide novel intermediates that may be used for synthesis of Trilaciclib, pharmaceutically acceptable salts or derivatives thereof. Aspects of the present disclosure also relate to a method for preparation of Trilaciclib intermediates. Further aspects of the present disclosure relate to method for preparation of Trilaciclib, pharmaceutically acceptable salts and derivatives thereof. Still further aspects of the present disclosure are drawn towards use of the Trilaciclib intermediates for the production of Trilaciclib, pharmaceutically acceptable salts or derivatives thereof.

BACKGROUND

[0002] Cyclin-Dependent Kinases (CDKs) are critical regulators of cell cycle progression and RNA transcription. A variety of genetic and epigenetic events cause universal over activity of the cell cycle CDKs in cancer, and their inhibition may lead to both cell cycle arrest and apoptosis.

[0003] T rilaciclib is a well-known anti-cancer molecule; a competitive inhibitor of cyclin-dependent kinases 4 and 6 (CDK4/6), with potential antineoplastic and chemoprotective activities. Specifically, it inhibits the activity of CDK4/6, thereby blocking the phosphorylation of the retinoblastoma protein (Rb) in early Gl; causing the cell cycle arrest in the Gl phase, induction of apoptosis, and inhibition of the proliferation of CDK4/6- overexpressing tumor cells.

[0004] Several methods have been reported for preparation of Trilaciclib intermediates, Trilaciclib, pharmaceutically acceptable salts, and derivatives thereof.

[0005] U.S. Patent No. 8,598,186, U.S. Patent No. 10,865,210, and WO published application 2020/041770 Al disclose preparation of Trilaciclib intermediates, Trilaciclib, pharmaceutically acceptable salts, and derivatives thereof. However, these methods suffer from various limitations such as low yield, generation of by-products, requirement of high amount of catalysts and solvents, multistage purification, and the likes.

[0006] Accordingly, a need is felt for new Trilaciclib intermediates, along with a new and improved method of preparation of Trilaciclib intermediates, Trilaciclib, pharmaceutically acceptable salts, and derivatives thereof. The present disclosure satisfies the existing needs, at least in part, and overcomes one or more disadvantages of the conventional approaches. Moreover, the present disclosure enables the production of Trilaciclib intermediates and Trilaciclib in good yields, and purity, wherein the process can be conducted economically using readily available and cost-effective reagents. For example, the process of the present disclosure uses propargyl alcohol which is more economical than propargylaldehyde diethyl acetal used in U.S. Patent No. 8,598, 186. Further the process of

U.S. Patent No. 8,598,186 employs TBAF in order to carry out the following conversion:

[0007] The use of TBAF typically results in the production of fluorinated impurities whereby the chlorine substituent is replaced by fluorine, for example potentially intermediates such as:

Such fluorinated impurities are minimized in the process of the present disclosure. [0008] Moreover, the process of the present disclosure enables the production of intermediates having very low metal impurities, thereby enabling the production of the final compound in high purity.

SUMMARY

[0009] Aspects of the present disclosure provide novel intermediates that may be used for synthesis of Trilaciclib, pharmaceutically acceptable salts or derivatives thereof. Aspects of the present disclosure also relate to a method for preparation of Trilaciclib intermediates. Further aspects of the present disclosure relate to method for preparation of Trilaciclib, pharmaceutically acceptable salts and derivatives thereof. Still further aspects of the present disclosure are drawn towards use of the Trilaciclib intermediates for the production of Trilaciclib, pharmaceutically acceptable salts or derivatives thereof.

[0010] An aspect of the present disclosure relates to a process for preparation of a compound of Formula I,

Formula I wherein PG represents a protecting group, said process comprising coupling a compound of Formula II with a compound of Formula III to obtain the compound of Formula I

Formula II Formula III

[0011] In some embodiments, the step of coupling the compound of Formula II with the compound of Formula III comprises: reacting the compound of Formula II with the compound of Formula III in presence of a Pd catalyst to obtain the compound of Formula I. [0012] In some embodiments, the process further comprises a step of purifying the compound of Formula I to obtain a substantially pure compound of Formula I. In some embodiments, the step of purifying comprises: (a) mixing the compound of Formula I with a first metal scavenger in presence of a solvent to obtain a mixture; (b) exposing the mixture to an elevated temperature under stirring conditions; (c) effecting filtration of the mixture to obtain a filtrate; (d) mixing the filtrate with a second metal scavenger in presence of an aqueous solution of a base to obtain a second mixture; and (e) effecting filtration of the second mixture to obtain the substantially pure compound of Formula I.

[0013] In some embodiments, the present invention comprises preparation of a compound of Formula II by reacting a compound of Formula IV with prop-2-yn-l-ol (propargyl alcohol).

[0014] In some embodiments, the step of obtaining the compound of Formula II comprises: (a) reacting the compound of Formula IV with prop-2-yn-l-ol in presence of a Pd based catalyst to obtain a compound of Formula V

Formula IV PG Formula V (b) effecting cyclization of a compound of Formula V to obtain a compound of Formula VI

(c) effecting oxidative cyclization of a compound of Formula VI to obtain a compound of

[0015] In some embodiments, PG represents a protecting group selected from t- butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, carbamate group, alkyl group, aryl group, allyl group, and aryl alkyl group. In some embodiments, PG represents t-butyloxycarbonyl (BOC) group. Alternatively, PG represents a protecting group selected from t-butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, carboxylic ester group [-C(=O)-OR, wherein R is alkyl or aryl as defined herein], alkyl group, aryl group, allyl group, and aryl alkyl group. Optionally, according to any aspect or embodiment, PG represents a protecting group selected from t-butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, alkyl group, aryl group, allyl group, and aryl alkyl group. In some embodiments, PG represents t- butyloxycarbonyl (BOC) group.

[0016] Another aspect of the present disclosure provides a compound of formula V

Formula V wherein PG represents a protecting group selected from t-butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, carbamate group, alkyl group, aryl group, allyl group, and aryl alkyl group. Alternatively, PG represents a protecting group selected from t-butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, carboxylic ester group [-C(=O)-OR, wherein R is alkyl or aryl as defined herein], alkyl group, aryl group, allyl group, and aryl alkyl group. Optionally, according to any aspect or embodiment, PG represents a protecting group selected from t-butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, alkyl group, aryl group, allyl group, and aryl alkyl group. In some embodiments, PG represents t- butyloxycarbonyl (BOC) group.

[0017] Another aspect of the present disclosure provides a compound of formula VI

wherein PG represents a protecting group selected from t-butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, carbamate group, alkyl group, aryl group, allyl group, and aryl alkyl group. Alternatively, PG represents a protecting group selected from t-butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, carboxylic ester group [-C(=O)-OR, wherein R is alkyl or aryl as defined herein], alkyl group, aryl group, allyl group, and aryl alkyl group. Optionally, according to any aspect or embodiment, PG represents a protecting group selected from t-butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, alkyl group, aryl group, allyl group, and aryl alkyl group. In some embodiments, PG represents t- butyloxycarbonyl (BOC) group.

[0018] Another aspect of the present disclosure provides a compound of formula I

wherein PG represents a protecting group selected from t-butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, carbamate group, alkyl group, aryl group, allyl group, and aryl alkyl group. Alternatively, PG represents a protecting group selected from t-butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, carboxylic ester group [-C(=O)-OR, wherein R is alkyl or aryl as defined herein], alkyl group, aryl group, allyl group, and aryl alkyl group. Optionally, according to any aspect or embodiment, PG represents a protecting group selected from t-butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, alkyl group, aryl group, allyl group, and aryl alkyl group. In some embodiments, PG represents t- butyloxycarbonyl (BOC) group. In some embodiments, the compound of formula l is a compound represented by formula IA

[0019] Further aspect of the present disclosure provides a crystalline form of compound

wherein the crystalline form has X-ray powder diffraction pattern comprising peaks at 5.8, 12.3, 13.8, 16.3, 19.3, 24.6 and 25.4 deg-2-theta ± 0.2 deg-2 -theta, and/or X-ray powder diffraction pattern; as shown in Figure 2.

[0020] Further aspect of the present disclosure provides a crystalline form of compound of Formula II A

wherein the crystalline form has X-ray powder diffraction pattern comprising peaks at 5.9, 9.6, 12.5, 17.2, 24.1, 25.0, 25.9 and 26.8 deg-2-theta ± 0.2 deg-2-theta, and/or X-ray powder diffraction pattern; as shown in Figure 1. [0021] Still further aspect of the present disclosure is drawn towards use of compound of formula I for manufacture of trilaciclib, pharmaceutically acceptable salt or derivative thereof

wherein PG represents a protecting group selected from t-butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, and carboxybenzyl (CBz) group. In some embodiments, PG represents t-butyloxycarbonyl (BOC) group. In some embodiments, the compound of formula l is a compound represented by formula IA

[0022] Still further aspect of the present disclosure is drawn towards use of compound of formula V for manufacture of trilaciclib or pharmaceutically acceptable salt.

Formula V wherein PG represents a protecting group selected from t-butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, and carboxybenzyl (CBz) group. In some embodiments, PG represents t-butyloxycarbonyl (BOC) group.

[0023] Still further aspect of the present disclosure is drawn towards use of compound of formula VI for manufacture of trilaciclib or pharmaceutically acceptable salt thereof

Formula VI wherein PG represents a protecting group selected from t-butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, and carboxybenzyl (CBz) group. In some embodiments, PG represents t-butyloxycarbonyl (BOC) group.

[0024] Still further aspect of the present disclosure is drawn towards use of crystalline form of a compound of Formula IA for manufacture of trilaciclib pharmaceutically acceptable salt or derivative thereof

[0025] Still further aspect of the present disclosure is drawn towards use of crystalline form of a compound of Formula IIA for manufacture of trilaciclib, pharmaceutically acceptable salt or derivative thereof

[0026] Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the exemplary embodiments of the invention.

BRIEF DESCRIPTION OF DRAWINGS

[0027] FIG. 1 illustrates an exemplary X-ray powder diffraction pattern (XRPD) of compound IIA, realized in accordance with an embodiment of the present disclosure.

[0028] FIG. 2 illustrates an exemplary X-ray powder diffraction pattern (XRPD) of compound IA, realized in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION

[0029] The following is a detailed description of embodiments of the present invention. The embodiments are in such detail as to clearly communicate the invention. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present invention as defined by the appended claims. [0030] Each of the appended claims defines a separate invention, which for infringement purposes is recognized as comprising equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the “invention” may in some cases refer to certain specific embodiments only. In other cases it will be recognized that references to the “invention” will refer to subject matter recited in one or more, but not necessarily all, of the claims.

[0031] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability.

[0032] Unless the context requires otherwise, throughout the specification which follow, the word “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense that is as “including, but not limited to.”

[0033] Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0034] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.

[0035] In some embodiments, the numbers expressing quantities of ingredients, properties such as concentration, and so forth, used to describe and claim certain embodiments of the invention are to be understood as being modified in some instances by the term “about”. Accordingly, in some embodiments, the numerical parameters set forth in the written description are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable.

[0036] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein.

[0037] The headings and abstract of the invention provided herein are for convenience only and do not interpret the scope or meaning of the embodiments.

[0038] All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.

[0039] The term ‘pharmaceutically acceptable salts” refers to an acid or base salt of the compound of the present disclosure, which salt possesses the desired pharmacological activity and is not biologically or otherwise undesirable. The salt can be formed with acids that include without limitation acetate, sulphate, adipate, alginate, aspartate, benzoate, benzenesulfonate, bisulfate butyrate, citrate, camphorate, camphorsulfonate, cyclopentanepropionate, digluconate, dodecyl sulfate, ethanesulfonate, fumarate, glucoheptanoate, glycerophosphate, hemisulfate, heptanoate, hexanoate, hydrochloride, dihydrochloride, dihydrobromide, hydrobromide, hydroiodide, 2-hydroxyethane-sulfonate, lactate, maleate, methanesulfonate, 2-naphthalenesulfonate, nicotinate, oxalate, thiocyanate, tosylate and undecanoate. Examples of a base salt include without limitation ammonium salts, alkali metal salts such as sodium and potassium salts, alkaline earth metal salts such as calcium and magnesium salts, salts with organic bases such as dicyclohexylamine salts, N- methyl-D-glucamine, and salts with amino acids such as arginine and lysine. In some embodiments, the basic nitrogen-containing groups can be quartemized with agents including lower alkyl halides such as methyl, ethyl, propyl and butyl chlorides, bromides and iodides; dialkyl sulfates such as dimethyl, diethyl, dibutyl and diamyl sulfates; long chain halides such as decyl, lauryl, myristyl and stearyl chlorides, bromides and iodides; and aralkyl halides such as phenethyl bromides and the likes. [0040] Preferably, the term “alkyl group” refers to a Ci to Cio alkyl group, or a Ci to Ce alkyl group, or a Ci to C4 alkyl group, or a Ci to C3 alkyl group, and preferably a methyl or ethyl group.

[0041] Preferably, the term “aryl group” refers to a Ce to Cio aryl group , or a Ce to Cs aryl group and more preferably phenyl.

[0042] Preferably, the term “allyl group” refers to -CH2-CH=CH2.

[0043] Preferably, the term “aryl alkyl group refers to a C7 to C12 aryl alkyl group, or a

C?to Cio aryl alkyl group; or a C?to Cio aryl alkyl group.

[0044] The term “derivative” refers to a compound or portion of the compound that is derived from or is theoretically derivable from the parent compound.

[0045] Aspects of the present disclosure provide novel intermediates that may be used for synthesis of Trilaciclib, pharmaceutically acceptable salts or derivatives thereof. Aspects of the present disclosure also relate to a method for preparation of Trilaciclib intermediates. Further aspects of the present disclosure relate to method for preparation of Trilaciclib, pharmaceutically acceptable salts and derivatives thereof. Still further aspects of the present disclosure are drawn towards use of the Trilaciclib intermediates for the production of Trilaciclib, pharmaceutically acceptable salts or derivatives thereof.

[0046] An aspect of the present disclosure relates to a process for preparation of a compound of Formula I,

wherein PG represents a protecting group, said process comprising coupling a compound of Formula II with a compound of Formula III to obtain the compound of Formula I

[0047] In some embodiments, the step of coupling the compound of Formula II with the compound of Formula III comprises: reacting the compound of Formula II with the compound of Formula III in presence of a Pd catalyst to obtain the compound of Formula I. [0048] In some embodiments, the step of coupling the compound of Formula II with the compound of Formula III comprises: reacting the compound of Formula II with the compound of Formula III in presence of a Pd catalyst, a base, and a solvent under an inert atmosphere at a temperature ranging from 80-100°C.

[0049] In some embodiments, the Pd catalyst is selected from Pd(OAc)2/(±)BINAP, Pd(OAc)2/PPh3, Pd(PPh3)4, Pd(ddpf)Ch CH2CI2, and Pd(PPh3)2C12. However, any other palladium based catalyst can also be used. In an embodiment, the Pd catalyst is Pd(OAc)₂/(±)BINAP.

[0050] In some embodiments, the base is an inorganic base. Exemplary inorganic bases include, but not limited to, potassium carbonate, sodium carbonate, potassium bicarbonate, potassium Zc/V-butoxide, cesium carbonate, and tripotassium phosphate. In an embodiment, the base is selected from potassium carbonate, tripotassium phosphate or mixtures thereof. In a preferred embodiment the base is potassium carbonate.

[0051] A step of coupling the compound of Formula II with the compound of Formula III, in accordance with an embodiment of the present disclosure, is schematically illustrated in Scheme 1 below:

Formula II Formula I

Scheme 1: Coupling a compound of Formula II with a compound of Formula III

[0052] In an embodiment, the step of coupling the compound of Formula II with the compound of Formula III comprises: (a) mixing the compound of Formula II with the compound of Formula III, a Pd catalyst, an inorganic base and a solvent under an inert atmosphere to form a reaction mixture; (b) stirring the reaction mixture at a temperature ranging from about 25°C to about 35°C; (c) heating the stirred reaction mixture to a temperature ranging from about 80°C to about 100°C to completion of the reaction; and (d) quenching the reaction mixture by: cooling the reaction mixture to a temperature ranging from about 50°C to about 60°C and effecting addition of a metal scavenger (such as, N-acetyl cysteine) and water to obtain a crude product mixture having the compound of Formula I. The crude product mixture may be subjected to filtration, and optionally washing, to obtain the compound of Formula I. In some embodiments, the metal scavenger is selected from: N- acetyl cysteine, a silica supported metal scavenger, polyamine resin, macroporous polystyrene-2,4,6- trimercaptotriazine (MP-TMT), microporous polystyrene-2,4,6- trimercaptotriazine, semiporous polystyrene-2,4,6- trimercaptotriazine (SP-TMT), ammonium pyrrolidinedithiocarbamate (APTDC), isopropyl xanthate salts and mixtures thereof. In particular, according to any aspect or embodiment of the process, the metal scavenger is selected from: N-acetyl cysteine, a silica supported metal scavenger, polyamine resin, microporous polystyrene-2,4,6- trimercaptotriazine, semiporous polystyrene-2,4,6- trimercaptotriazine (SP-TMT), ammonium pyrrolidinedithiocarbamate (APTDC), isopropyl xanthate salts and mixtures thereof. For example, the silica supported metal scavenger may be a silica gel which is derivatized by various functional groups, including thiol, (i.e. thiol - derivatized silica gel, SiliaMetS® thiol), triamine (i.e. thiamine-derivatized silica gel, SiliaMetS® Triamine), (R)-cysteine (i.e. (R)-cysteine -derivatized silica gel, SiliaMetS® (R) Cysteine), triaminetetraacetic acid (i.e. triaminetetraacetic acid-derivatized silica gel, SiliaMetS® TAAcOH), triaminetetraacetic acid, sodium salt (i.e. triaminetetraacetic acid, sodium salt-derivatized silica gel, SiliaMetS® TAAcONa), 2,4,6-trimercaptotriazine (i.e.

2.4.6-Trimercaptotriazine-derivatized silica gel, Si-TMT), or propylsulphonic acid (i.e. propylsulphonic acid-silica gel, Si-propylsulphonic acid).

[0053] Particularly, the silica supported metal scavenger may be: a thiol-derivatized silica gel, a triamine-derivatized silica gel, a (R)-cysteine-derivatized silica gel, a tri aminetetraacetic acid-derivatized silica gel, a triaminetetraacetic acid- derivatized silica gel, a sodium salt-derivatized silica gel, a 2,4,6-trimercaptotriazine-derivatized silica gel, or a propylsulphonic acid-derivatized silica gel. Exemplary silica supported metal scavengers suitable for the present disclosure include, but not limited to, SiliaMetS® Triamine, SiliaMetS® Thiol, SiliaMetS® (R) Cysteine, SiliaMetS® TAAcOH, SiliaMetS® TAAcONa,

2.4.6-Trimercaptotriazine Silica Gel (Si-TMT), and Si-propylsulphonic acid. According to any aspect of the process, the metal scavenger is selected from thiol-derivatized silica gel, or N-acetyl cysteine.

[0054] In some embodiments, the process further comprises a step of purifying the compound of Formula I to obtain a substantially pure compound of Formula I. In some embodiments, the purification process comprises the use of at least one metal scavenger. In some embodiments, the step of purifying comprises: (a) mixing the compound of Formula I with a first metal scavenger in presence of a solvent to obtain a mixture; (b) exposing the mixture to an elevated temperature under stirring conditions; (c) effecting filtration of the mixture to obtain the filtrate; (d) mixing the filtrate with a second metal scavenger in presence of an aqueous solution of a base to obtain a second mixture; and (e) effecting filtration of the second mixture to obtain the substantially pure compound of Formula I. In some embodiments, the substantially pure compound of Formula I is in form of crystals. [0055] In some embodiments, the first metal scavenger and second metal scavenger are same or different, and selected independently from: N-acetyl cysteine, a silica supported metal scavenger, polyamine resin, macroporous polystyrene-2,4,6- trimercaptotriazine (MP- TMT), microporous polystyrene-2,4,6- trimercaptotriazine, semiporous polystyrene-2,4,6- trimercaptotriazine (SP-TMT), ammonium pyrrolidinedithiocarbamate (APTDC), isopropyl xanthate salts and mixtures thereof. Exemplary silica supported metal scavengers suitable for the present disclosure include, but not limited to, SiliaMetS® Triamine, SiliaMetS® Thiol, SiliaMetS® (R) Cysteine, SiliaMetS® TAAcOH, SiliaMetS® TAAcONa, 2,4,6- Trimercaptotriazine Silica Gel (Si-TMT), and Si-propylsulphonic acid. In particular, according to any aspect or embodiment of the process, the first and second metal scavenger can be the same or different and are independently selected from: N-acetyl cysteine, a silica supported metal scavenger, polyamine resin, microporous polystyrene-2,4,6- trimercaptotriazine, semiporous polystyrene-2,4,6- trimercaptotriazine (SP-TMT), ammonium pyrrolidinedithiocarbamate (APTDC), isopropyl xanthate salts and mixtures thereof. For example, the silica supported metal scavenger may be a silica gel which is derivatized by various functional groups, including thiol, (i.e. thiol-derivatized silica gel, SiliaMetS® thiol), triamine (i.e. thiamine-derivatized silica gel, SiliaMetS® Triamine), (R)- cysteine (i.e. (R)-cysteine -derivatized silica gel, SiliaMetS® (R) Cysteine), triaminetetraacetic acid (i.e. triaminetetraacetic acid-derivatized silica gel, SiliaMetS® TAAcOH), triaminetetraacetic acid, sodium salt (i.e. triaminetetraacetic acid, sodium salt- derivatized silica gel, SiliaMetS® TAAcONa), 2,4,6-trimercaptotriazine (i.e. 2,4,6- Trimercaptotriazine-derivatized silica gel, Si-TMT), or propylsulphonic acid (i.e. propylsulphonic acid-silica gel, Si-propylsulphonic acid).

[0056] Particularly, the silica supported metal scavenger may be: a thiol-derivatized silica gel, a triamine-derivatized silica gel, a (R)-cysteine-derivatized silica gel, a tri aminetetraacetic acid-derivatized silica gel, a triaminetetraacetic acid- derivatized silica gel, a sodium salt-derivatized silica gel, a 2,4,6-trimercaptotriazine-derivatized silica gel, or a propylsulphonic acid-derivatized silica gel. Exemplary silica supported metal scavengers suitable for the present disclosure include, but not limited to, SiliaMetS® Triamine, SiliaMetS® Thiol, SiliaMetS® (R) Cysteine, SiliaMetS® TAAcOH, SiliaMetS® TAAcONa, 2,4,6-Trimercaptotriazine Silica Gel (Si-TMT), and Si-propylsulphonic acid. According to any aspect of the process, the first and second metal scavenger are selected from thiol- derivatized silica gel or N-acetyl cysteine.

[0057] In some embodiments, the first metal scavenger is a silica supported metal scavenger, preferably thiol-derivatized silica gel. In some embodiments, the second metal scavenger is N-acetyl cysteine. In some embodiments, the solvent comprises: toluene, and any or a combination of DMSO and DMF. In an embodiment, the solvent comprises a mixture of toluene and DMSO. In another embodiment, the solvent comprises a mixture of toluene and DMF.

[0058] In an embodiment, the step of purifying comprises: (a) mixing the compound of Formula I with a silica supported metal scavenger in presence of a solvent to obtain a mixture, the solvent being a mixture of toluene and any of DMSO and DMF; (b) exposing the mixture to an elevated temperature ranging from about 90°C to about 120°C under stirring conditions; (c) effecting filtration of the mixture to obtain the filtrate; (d) mixing the filtrate with N-acetyl cysteine in presence of an aqueous solution of a base under stirring conditions maintaining a temperature between about 50°C to about 70°C to obtain a second mixture; and (e) effecting filtration of the second mixture to obtain the substantially pure compound of Formula I. In some embodiments, the substantially pure compound of Formula I is in form of crystals; as shown for example in Figure 2.

[0059] In some embodiments, present invention includes the preparation of the compound of Formula II by reacting a compound of Formula IV with prop-2-yn-l-ol (propargyl alcohol).

[0060] In some embodiments, the step of obtaining the compound of Formula II comprises: (a) reacting the compound of Formula IV with prop-2-yn-l-ol in presence of a Pd based catalyst to obtain a compound of Formula V

Formula IV PG Formula V

(b) effecting cyclization of a compound of Formula V to obtain a compound of Formula VI

and

Formula II

[0061] In some embodiments, the step of obtaining the compound of Formula II comprises: (a) reacting the compound of Formula IV with prop-2-yn-l-ol in presence of a Pd based catalyst to obtain a compound of Formula V; (b) effecting cyclization of a compound of Formula V to obtain a compound of Formula VI; and (c) effecting oxidative cyclization of a compound of Formula VI to obtain a compound of Formula II. The process steps (b) and (c) can be carried out without purification of the products of steps (a) and (b) respectively. For example, the products in steps (a) and (b) can be isolated directly from the reaction steps by distillation following any quenching step. The products can be used in the subsequent step without further purification.

[0062] The compound of Formula IV can be prepared according to any of the methods known in the art, for example, the method(s) as disclosed in US 8,598,186 B2, contents whereof are incorporated herein, in its entirety, by way of reference.

[0063] In some embodiments, the Pd based catalyst is selected from Pd(OAc)2/(±)BINAP, Pd(OAc)₂/PPh₃, Pd(PPh₃)₄, Pd(ddpf)Ch CH2CI2, and Pd(PPh3)₂Cl₂. However, any other palladium based catalyst can also be used. In an embodiments, the Pd based catalyst is Pd(PPh₃)2Ch.

[0064] In some embodiments, the step of cyclization of a compound of Formula V is effected in presence of tetra-n-butylammonium fluoride (TBAF) and a solvent.

[0065] In some embodiments, the step of effecting oxidative cyclization of a compound of Formula VI comprises exposing the compound of Formula VI to an elevated temperature in presence of an oxidant. In some embodiments, the oxidant is selected from: Oxone/NaCl, NaOCl/TEMPO, MnO2/Oxone/Na2CO₃, MnO2/Oxone/NaHCO₃, 2-Iodoxy benzoic acid (IDB), Eaton’s reagent, IDB/TEMPO, hydrogen peroxide, bis(acetoxy)iodobenzene (BAIB)/ (2,2,6,6-tetramethylpiperidin-l-yl)oxidanyl (TEMPO) or mixtures thereof. In an embodiment, the oxidant comprises a combination of Bis(acetoxy)iodobenzene (BAIB) and (2, 2,6,6- tetramethylpiperidin- 1 -yl)oxidanyl (TEMPO).

[0066] The oxidative cyclization step may preferably be carried out in a solvent selected from the group consisting of: water, cyclohexane, chloroform, toluene, xylene, ethylbenzene, diethyl ether, diisopropyl ether, methyl tert-butyl ether, ethyl acetate, isopropyl acetate, n- butyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone, methylene dichloride (MDC), 2-methyl tetrahydrofuran (2 -Me THF), tetrahydrofuran, and 1,4-di oxane, and mixtures thereof. Particularly, the oxidative cyclization step may be carried out in a solvent selected from the group consisting of: water, cyclohexane, chloroform, toluene, xylene, ethylbenzene, diethyl ether, diisopropyl ether, methyl tert-butyl ether, ethyl acetate, isopropyl acetate, n-butyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, methylene dichloride (MDC), 2-methyl tetrahydrofuran (2 -Me THF), tetrahydrofuran, or mixtures thereof. The oxidative cyclization step may more particularly be carried out in a solvent selected from the group consisting of: water, diethyl ether, diisopropyl ether, methyl tertbutyl ether, ethyl acetate, isopropyl acetate, and n-butyl acetate; or a solvent selected from the group consisting of: water, ethyl acetate, isopropyl acetate, and n-butyl acetate, or mixtures thereof. According to any aspect or embodiment, the oxidative cyclization step is carried out in a solvent selected from the group consisting of: water, ethyl acetate, isopropyl acetate, and n-butyl acetate, and more preferably a mixture comprising water, and one or more of ethyl acetate, isopropyl acetate, and n-butyl acetate; or a mixture of water and ethylacetate.

[0067] Advantageously, the oxidative cyclization step of the present disclosure enables the cyclization following oxidation to be effected spontaneously (i.e. in situ), and thus without the need to use another reagent such as an acid.

[0068] In an embodiment, the step of reacting the compound of Formula IV with prop-2- yn-l-ol comprises: (a) mixing the compound of Formula IV, prop-2-yn-l-ol and TBAF in presence of a solvent under an inert atmosphere; (b) effecting addition of a Pd based catalyst to obtain a reaction mixture; and (c) heating the reaction mixture at a temperature ranging from about 50°C to about 70°C to obtain the compound of Formula V. In some embodiments, the compound of Formula V is directly subjected to the step of cyclization without any intermittent purification step. In some embodiments, the compound of Formula V is purified before subjecting to the step of cyclization. [0069] In an embodiment, the step of effecting cyclization of the compound of Formula V comprises: (a) mixing the compound of Formula V with TBAF in presence of a solvent to obtain a reaction mixture; and (b) heating the reaction mixture at a temperature ranging from about 60°C to about 80°C to obtain the compound of Formula VI. In some embodiments, the compound of Formula VI is directly subjected to the step of oxidative cyclization without any intermittent purification step. In some embodiments, the compound of Formula VI is purified before subjecting to the step of cyclization.

[0070] In an embodiment, the step of effecting oxidative cyclization of the compound of Formula VI comprises: (a) preparing a solution of the compound of Formula VI; (b) cooling the solution to a temperature ranging from about 10°C to about 20°C; (c) effecting addition of Bis(acetoxy)iodobenzene (BAIB) and a solution of (2,2,6,6-Tetramethylpiperidin-l- yljoxyl (TEMPO) to the cooled solution to obtain a reaction mixture; and (d) raising temperature of the reaction mixture to a temperature ranging from about 20°C to about 30°C to obtain the compound of Formula II.

[0071] A process for obtaining the compound of Formula II, in accordance with an embodiment of the present disclosure, is schematically illustrated in Scheme 2 below:

Scheme 2: Process for preparation of a compound of Formula II

[0072] In some embodiments, PG represents a protecting group selected from t- butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, carbamate group, alkyl group, aryl group, allyl group, and aryl alkyl group. In some embodiments, PG represents t-butyloxycarbonyl (BOC) group. According to any aspect or embodiment, PG represents a protecting group selected from t-butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, carboxylic ester group [-C(=O)-OR, wherein R is alkyl or aryl as defined herein], alkyl group, aryl group, allyl group, and aryl alkyl group. In some embodiments, PG represents a protecting group selected from t-butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, alkyl group, aryl group, allyl group, and aryl alkyl group. In some embodiments, PG represents t-butyloxycarbonyl (BOC) group.

[0073] Another aspect of the present disclosure relates to a process for preparation of a hydrate form of Trilaciclib salt, the process comprises:

(a) contacting a solution of a compound of Formula I with an acid at a temperature ranging from about 15°C to about 35°C to obtain a reaction mixture

Formula I wherein PG represents a protecting group;

(b) heating the reaction mixture to a temperature ranging from about 40°C to 70°C to obtain a crude product mixture;

(c) effecting filtration of the crude product mixture to obtain a filtrate;

(d) adding the filtrate to a pre-cooled organic solvent to obtain a solution;

(e) stirring the solution at a temperature ranging from about 0°C to about 10°C for a first time period to obtain a suspension; and

(f) effecting filtration of the suspension to obtain a hydrate form of Trilaciclib salt. [0074] In some embodiment, the acid is concentrated HC1 and the Trilaciclib salt is Trilaciclib dihydrochloride. In some embodiments, PG represents a protecting group selected from t-butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, carbamate group, alkyl group, aryl group, allyl group, and aryl alkyl group. Alternatively, PG represents a protecting group selected from t-butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, carboxylic ester group [-C(=O)-OR, wherein R is alkyl or aryl as defined herein], alkyl group, aryl group, allyl group, and aryl alkyl group. Optionally, according to any aspect or embodiment, PG represents a protecting group selected from t-butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, alkyl group, aryl group, allyl group, and aryl alkyl group. In some embodiments, PG represents t- butyloxycarbonyl (BOC) group.

[0075] In some embodiments, the compound of Formula I is a compound represented by a structure of Formula I A

Formula IA

[0076] In some embodiments, the hydrate form of Trilaciclib dihydrochloride is Trilaciclib dihydrochloride pentahydrate.

[0077] In an embodiment, the process comprises: (a) contacting a solution of a compound of Formula I in methanol and water with concentrated HC1 at a temperature ranging from about 20°C to about 30°C to obtain a reaction mixture; (b) heating the reaction mixture to a temperature ranging from about 50°C to 60°C to obtain a crude product mixture; (c) effecting filtration of the crude product mixture to obtain a filtrate; (d) adding the filtrate to a pre-cooled organic solvent to obtain a solution; (e) stirring the solution at a temperature ranging from about 0°C to about 10°C for a time period ranging from 1 hour to 5 hours to obtain a suspension; and (f) effecting filtration of the suspension to obtain a hydrate form of Trilaciclib dihydrochloride.

[0078] Another aspect of the present disclosure relates to a process for preparation of Trilaciclib or salt thereof, the process comprises:

Formula I wherein PG represents a protecting group;

(b) heating the reaction mixture to a temperature ranging from about 40°C to 70°C to form a mixture comprising an acid addition salt of Trilaciclib; and

(c) optionally, contacting the mixture with a base solution maintaining a temperature ranging from about 40°C to 70°C to obtain Trilaciclib.

[0079] In some embodiments, PG represents a protecting group selected from t- butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group carbamate group, alkyl group, aryl group, allyl group, and aryl alkyl group. Alternatively, PG represents a protecting group selected from t-butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, carboxylic ester group [-C(=O)-OR, wherein R is alkyl or aryl as defined herein], alkyl group, aryl group, allyl group, and aryl alkyl group. Optionally, according to any aspect or embodiment, PG represents a protecting group selected from t-butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, alkyl group, aryl group, allyl group, and aryl alkyl group. In some embodiments, PG represents t- butyloxycarbonyl (BOC) group.

[0080] In some embodiments, the compound of Formula I is a compound represented by a structure of Formula I A

[0081] In some embodiments, the acid is concentrated sulfuric acid and the acid addition salt of Trilaciclib is Trilaciclib sulphate salt. In some embodiments, the acid is concentrated hydrobromic acid and the acid addition salt of Trilaciclib is Trilaciclib dihydrobromide salt.

[0082] In some embodiments, the base solution is selected from an aqueous solution of KOH, NaOH, Na2CO3, K2CO3 or mixtures thereof. However, any other aqueous solution of base can also be used.

[0083] In some embodiments, the acid addition salt of Trilaciclib is isolated. In some embodiments, Trilaciclib is obtained directly from the compound of Formula I without isolation of the acid addition salt of Trilaciclib. In some embodiment, Trilaciclib is further converted into a different acid addition salt.

[0084] Another aspect of the present disclosure relates to a process for preparation of Trilaciclib or salt thereof, the process comprising:

(a) reacting the compound of Formula IV with prop-2-yn-l-ol in presence of a Pd based catalyst to obtain a compound of Formula V

Formula II

(d) coupling a compound of Formula II with a compound of Formula III to obtain the compound of Formula I

(e) effecting treatment of the compound of Formula I to obtain Trilaciclib or salt thereof. [0085] In some embodiments, the step of effecting treatment of the compound of Formula I comprises effecting treatment of the compound of Formula I to obtain Trilaciclib or salt thereof, said treatment comprises the steps as detailed hereinabove. This step may involves the isolation of Trilaciclib free base which, optionally, can be further converted into a salt of trilaciclib (for example: Trilaciclib hydrochloride salt, Trilaciclib besylate salt, Trilaciclib mesylate salt, Trilaciclib sulfate salt, Trilaciclib citrate salt etc. ; preferably Trilaciclib hemicitrate salt). Alternately, Formula I can be converted directly (i.e., without isolating Trilaciclib free base) to Trilaciclib salt (for example, Trilaciclib DiHCl; preferably Trilaciclib dihydrochloride pentahydrate).

[0086] The process for preparation of Trilaciclib or salt thereof is schematically shown in Scheme 3 below:

Scheme 3: Preparation of Trilaciclib or salt thereof

[0087] Another aspect of the present disclosure provides a compound of formula V

[0088] Another aspect of the present disclosure provides a compound of formula VI

[0089] Another aspect of the present disclosure provides a compound of formula I

wherein PG represents a protecting group selected from t-butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, carbamate group, alkyl group, aryl group, allyl group, and aryl alkyl group. In some embodiments, PG represents t-butyloxycarbonyl (BOC) group. Alternatively, PG represents a protecting group selected from t-butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, carboxylic ester group [-C(=O)-OR, wherein R is alkyl or aryl as defined herein], alkyl group, aryl group, allyl group, and aryl alkyl group. Optionally, according to any aspect or embodiment, PG represents a protecting group selected from t- butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, alkyl group, aryl group, allyl group, and aryl alkyl group. In some embodiments, the compound of formula l is a compound represented by formula IA

[0090] Further aspect of the present disclosure provides a crystalline form of compound

[0091] Further aspect of the present disclosure provides a crystalline form of compound of Formula II A

wherein the crystalline form has X-ray powder diffraction pattern comprising peaks at 5.9, 9.6, 12.5, 17.2, 24.1, 25.0, 25.9 and 26.8 deg-2 -theta ± 0.2 deg-2-theta, and/or X-ray powder diffraction pattern; as shown in Figure 1.

[0092] Still further aspect of the present disclosure is drawn towards use of compound of formula I for manufacture of trilaciclib, pharmaceutically acceptable salt or derivative thereof

[0093] Still further aspect of the present disclosure is drawn towards use of compound of formula V for manufacture of trilaciclib or pharmaceutically acceptable salt thereof

Formula V wherein PG represents a protecting group selected from t-butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, carbamate group, alkyl group, aryl group, allyl group, and aryl alkyl group. Alternatively, PG represents a protecting group selected from t-butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, carboxylic ester group [-C(=O)-OR, wherein R is alkyl or aryl as defined herein], alkyl group, aryl group, allyl group, and aryl alkyl group. Optionally, according to any aspect or embodiment, PG represents a protecting group selected from t-butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, alkyl group, aryl group, allyl group, and aryl alkyl group. In some embodiments, PG represents t- butyloxycarbonyl (BOC) group. [0094] In some embodiments, the compound of formula V may be subjected to cyclization to obtain a compound of formula VI, which can then be subjected to oxidative cyclization to obtain a compound of Formula II. The compound of Formula II can be coupled with the compound of Formula III to obtain the compound of Formula I. The compound of Formula I can then be deprotected to obtain Trilaciclib free base. Alternatively, the compound of Formula I can be appropriately treated, for example, as described in embodiments hereinabove, to obtain Trilaciclib salt or hydrate thereof. Still alternatively, the Trilaciclib free base can be appropriately treated, for example, as described in embodiments hereinabove, to obtain Trilaciclib salt or hydrate thereof.

[0095] Still further aspect of the present disclosure is drawn towards use of compound of formula VI for manufacture of trilaciclib or pharmaceutically acceptable salt thereof

[0096] In some embodiments, the compound of formula VI can be subjected to oxidative cyclization to obtain a compound of Formula II. The compound of Formula II can be coupled with the compound of Formula III to obtain the compound of Formula I. The compound of Formula I can then be deprotected to obtain Trilaciclib free base. Alternatively, the compound of Formula I can be appropriately treated, for example, as described in embodiments hereinabove, to obtain Trilaciclib salt or hydrate thereof. Still alternatively, the Trilaciclib free base can be appropriately treated, for example, as described in embodiments hereinabove, to obtain Trilaciclib salt or hydrate thereof.

[0097] Still further aspect of the present disclosure is drawn towards use of crystalline form of a compound of Formula IA for manufacture of trilaciclib, pharmaceutically acceptable salt or derivative thereof

[0098] Still further aspect of the present disclosure is drawn towards use of crystalline form of a compound of Formula IIA for manufacture of trilaciclib, pharmaceutically acceptable salt or derivative thereof

[0099] Non-limiting examples of the solvent that may be useful in the processes of the present disclosure includes, but not limited to, water, cyclohexane, chloroform, toluene, xylene, ethylbenzene, diethyl ether, diisopropyl ether, methyl tert-butyl ether, methanol, ethanol, isopropanol, ethyl acetate, isopropyl acetate, n-butyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, dimethylformamide (DMF), dimethylacetamide (DMAc or DMA), dimethyl sulfoxide (DMSO), N-methyl-2-pyrrolidone (NMP), methylene di chloride (MDC), 2-methyl tetrahydrofuran (2 -Me THF), tetrahydrofuran (THF), triethylamine (TEA), 1,4-di oxane, and mixtures thereof. Alternatively, unless otherwise indicated, solvents that may be useful in the processes of the present disclosure are: water, cyclohexane, chloroform, toluene, xylene, ethylbenzene, diethyl ether, diisopropyl ether, methyl tert-butyl ether, methanol, ethanol, isopropanol, n-butanol, tert-butanol, ethyl acetate, isopropyl acetate, n- butyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, dimethylformamide (DMF), dimethylacetamide (DMAc or DMA), dimethyl sulfoxide (DMSO), N-methyl-2- pyrrolidone (NMP), methylene di chloride (MDC), 2-methyl tetrahydrofuran (2 -Me THF), tetrahydrofuran (THF), tri ethylamine (TEA), 1,4-di oxane, and mixtures thereof.

EXAMPLES Example 1: Preparation of tert-butyl 2^,-chloro-6^,-oxo-6^,H-SDiro[cyclohexane-l■,9^,- pyrazino | .,2^,:l.,5]pyrrolo[2.,3-d]pyrimidine]-7^,(8^,H)-carboxylate (a compound of Formula IIA)

[00100] Tert-butyl ((l-((5-bromo-2-chloropyrimidin-4-yl)amino)cyclohexyl)methyl) carbamate (a compound of Formula IV, 100 grams), prop-2-yn-l-ol (propargyl alcohol) (33.38 grams) and TBAF 3H2O (187.9 grams) were added to 2-methyl tetrahydrofuran (1200 ml) and the mixture was stirred for 20-30 minutes under nitrogen atmosphere. Pd(PPh3)2C12 (5.01 grams) was added, and the mixture was heated to 50-55°C. After completion of the reaction, the reaction mixture was cooled to 20-30°C and washed with water (250 ml x 2). Organic phase was distilled under vacuum to obtain oily residue of tert-butyl ((l-((2-chloro- 5-(3 -hydroxyprop- 1 -yn- 1 -yl)pyrimidin-4-yl)amino) cyclohexyl)methyl)carbamate (a compound of Formula V, 130.0 grams). Purity by HPLC was found to be >84.0%.

[00101] To the crude oily residue (a compound of Formula V), 2-methyl tetrahydrofuran (1800 ml) and TBAF 3H2O (270.60 grams) were added, and the reaction mixture was heated to 70-78°C. After reaction completion, the mixture was cooled to 20-30°C and washed with water (1000 ml). Organic phase was distilled under vacuum to obtain about 150g of oily compound-tert-butyl ((l-(2-chloro-6-(hydroxymethyl)-7H-pyrrolo[2,3-d]pyrimidin-7- yl)cy cl ohexyl)m ethyl) carbamate (a compound of Formula VI). Purity by HPLC was found to be >70.0%.

[00102] The obtained compound (a compound of Formula VI) was dissolved in ethyl acetate (1000 ml) and water (100 ml) was added thereto. Reaction mixture was then cooled to 10-20°C and Bis(acetoxy)iodobenzene (BAIB) (245.6 grams) was added, followed by addition of a solution of (2,2,6,6-tetramethylpiperidin-l-yl)oxidanyl (TEMPO) (14.89 grams) in ethyl acetate (200ml). Reaction temperature was raised to 20-30°C. After reaction completion, the organic layer was washed with saturated solution of sodium sulphite, sodium bicarbonate and sodium chloride solution. The organic layer was distilled out under vacuum to obtain brown oily colored residue (HPLC purity was found to be >75.0%), which was further purified in isopropyl alcohol (200ml) followed by toluene (180ml) to obtain about 30 g of light yellow colored crystals of tert-butyl 2'-chloro-6'-oxo-6'H-spiro[cyclohexane-l,9'- pyrazino[r,2': l,5]pyrrolo[2,3-d]pyrimidine]-7'(8'H)-carboxylate (a compound of Formula IIA) having HPLC purity of about 99.40%. Characteristic X-ray powder diffraction pattern (XRPD) of compound IIA is provided in FIG. 1. The overall reaction is schematically shown in scheme 4 below:

Scheme 4: Preparation of a compound of Formula IIA

Example 2: Preparation of tert-butyl 2^,-((5-(4-methylpiperazin-l-yl)pyridin-2- yl)amino)-6^,-oxo-6^,H-spiro[cyclohexane-l.,9^,-pyrazino[l^,.,2^,:l.,5]pyrrolo[2.,3- d|pyrimidine|-7'(8'll)-carboxylate (a compound of Formula IA)

[00103] To a mixture of tert-butyl 2'-chloro-6'-oxo-6'H-spiro[cyclohexane-l,9'-pyrazino [T,2': l,5]pyrrolo[2,3-d]pyrimidine]-7'(8'H)-carboxylate (a compound of Formula IIA, 100g) and 5-(4-methylpiperazin-l-yl)pyridin-2-amine (a compound of Formula III, 73.79 grams) in toluene (1000 ml) were added: potassium carbonate (56.57 grams), Pd(OAc)2 (1.44 grams) and (±)-2,2'-Bis(diphenylphosphino)-l,1 '-binaphthalene ((±) BINAP, 7.96 grams) under nitrogen atmosphere and the reaction mixture was stirred for 15-30 minutes at 25-35°C.

Reaction mixture was heated to 85-95°C and after the reaction was completed (monitored by HPLC), it was cooled to 50-60°C and N-acetyl cysteine (10 grams) and water (1000 ml) were added. Reaction mixture was stirred for 2-3 hours followed by cooling and stirring to get a suspension. The reaction mixture was filtered, washed with toluene (300 ml), and dried to obtain pale yellow crystalline powder of tert-butyl 2'-((5-(4-methylpiperazin-l-yl)pyridin-2- yl)amino)-6'-oxo-6'H-spiro[cyclohexane- 1 ,9'-pyrazino[ l',2' : 1 ,5]pyrrolo[2,3 -d]pyrimidine]- 7'(8'H)-carboxylate (a compound of Formula IA); HPLC purity was found to be >98.0%. The reaction is schematically shown in scheme 5 below:

Scheme 5: Preparation of a compound of Formula IA

Example 3: Purification of tert-butyl 2^,-((5-(4-methylpiperazin-l-yl)pyridin-2- yl)amino)-6^,-oxo-6^,H-spiro[cvclohexane-l.,9^,-pyrazino[l^,.,2^,:l.,5]pyrrolo[2.,3- d]pyrimidine]-7^,(8^,H)-carboxylate (a compound of Formula IA)

[00104] Tert-butyl 2'-((5-(4-methylpiperazin-l -yl)pyri din-2 -yl)amino)-6'-oxo-6'H- spiro[cyclohexane- 1 ,9'-pyrazino[ l',2' : 1 ,5]pyrrolo[2,3 -d]pyrimidine]-7'(8'H)-carboxylate (a compound of Formula IA, 100g) and SiliaMetS® thiol (15 grams) were stirred in a mixture of toluene (1500 ml) and DMF (500ml). Reaction temperature was raised to about 100°C and maintained with stirring for 2-3 hours. The mixture was filtered through hyflo bed at about 100°C and the filtrate was cooled to 50-60°C (to obtain suspension). 1% potassium carbonate solution (1000ml) and N-acetyl cysteine (5 grams) were added to the suspension and the mixture was stirred for about 2.5 hours at 50-60°C. The mixture was cooled to 20-30°C, stirred for 2-3 hours, filtered and dried to obtain pale yellow crystals of tert-butyl 2'-((5-(4- methylpiperazin-l-yl)pyri din-2 -yl)amino)-6'-oxo-6'H-spiro[cyclohexane- 1,9'- pyrazino[r,2': l,5]pyrrolo[2,3-d]pyrimidine]-7'(8'H)-carboxylate (a compound of Formula IA, 90 grams) having HPLC purity >99.0%. Characteristic X-ray powder diffraction pattern (XRPD) of the resultant compound (of formula IA) is provided in FIG. 2.

Example 4: Purification of tert-butyl 2^,-((5-(4-methylpiperazin-l-yl)pyridin-2- yl)amino)-6^,-oxo-6^,H-spiro[cvclohexane-l.,9^,-pyrazino[l^,.,2^,:l.,5]pyrrolo[2.,3- d|pyrimidine|-7'(8'II)-carboxylate (a compound of Formula IA)

[00105] Tert-butyl 2'-((5-(4-methylpiperazin-l -yl)pyri din-2 -yl)amino)-6'-oxo-6'H- spirofcyclohexane- 1 ,9'-pyrazino[ l',2' : 1 ,5]pyrrolo[2,3 -d]pyrimidine]-7'(8'H)-carboxylate (a compound of Formula IA, 100 grams) and SiliaMetS® thiol (15 grams) were stirred in a mixture of toluene (1500 ml) and DMSO (500 ml). Reaction was heated to 100-110°C, stirred for 2-3 hours and filtered through hyflo bed at 100-110°C. The filtrate was cooled to 50-60°C (suspension was obtained), 1% Potassium carbonate solution (1000 ml) and N- acetyl cysteine (5 grams) were added and the mixture was stirred about 2.5 hours. The reaction mixture was cooled to 20-30°C, stirred, and dried to obtain pale yellow colored crystals of tert-butyl 2'-((5-(4-methylpiperazin-l-yl)pyridin-2-yl)amino)-6'-oxo-6'H- spirofcyclohexane- 1 ,9'-pyrazino[ l',2' : 1 ,5]pyrrolo[2,3 -d]pyrimidine]-7'(8'H)-carboxylate (a compound of Formula IA, 90 grams) having HPLC purity >99.0%.

Example 5: Preparation of 2^,-((5-(4-methylpiperazin-l-yl)pyridin-2-yl)amino)-7^,,8^,- dihydro -6'II- 6'-one

(Trilaciclib free base)

[00106] To tert-butyl 2'-((5-(4-methylpiperazin-l-yl)pyridin-2-yl)amino)-6'-oxo-6'H- spirofcyclohexane- 1 ,9'-pyrazino[ l',2' : 1 ,5]pyrrolo[2,3 -d]pyrimidine]-7'(8'H)-carboxylate (a compound of Formula IA, 100 grams) in water (2500 ml), concentrated sulfuric acid (44.86 grams) was added at 20-30°C and the reaction was heated to 50-60°C. After reaction completion, 25% aq. potassium carbonate solution (500 ml) and N-acetyl cysteine (5 grams) were added at 50-60°C. Reaction mixture was stirred for 2-3 hours, filtered and dried under vacuum at 55-65°C to obtain an off white solid 2'-((5-(4-methylpiperazin-l-yl)pyridin-2- yl)amino)-7', 8'-dihydro-6'H-spiro[cyclohexane- 1 ,9'-pyrazino[ l',2' : 1 , 5]pyrrolo[2,3 - d]pyrimidin]-6'-one (Trilaciclib free base, 80 grams) with HPLC purity of >99.50%.

Example 6: Preparation of 2^,-((5-(4-methylpiperazin-l-yl)pyridin-2-yl)amino)-7^,,8^,- dihydro-6^,H-spiro [cyclohexane- pyrazino [1 ’,2’ : 1,5] pyrrolo [2, 3-d] pyrimidin]-6^,-one

dihydrochloride pentahydrate (Trilaciclib dihydrochloride pentahydrate or THC16, as disclosed in WQ20220076779)

[00107] 2'-((5-(4-methylpiperazin- 1 -yl)pyri din-2 -yl)amino)-7',8'-dihydro-6'H-spiro

[cyclohexane-l,9'-pyrazino[r,2': l,5]pyrrolo[2,3-d]pyrimidin]-6'-one (Trilaciclib free base, 10 g), methanol (350 ml), water (150 ml) and concentrated HC1 (8.1ml) were stirred at 20-30°C for 5-10 minutes. The mixture was heated to 45-55°C for 30-60 minutes and filtered through 0.2p filter paper. The obtained filtrate was added into pre-cooled ethyl acetate (150 ml) and stirred for 2-3 hours at 0-5°C. The solid was filtered and dried under vacuum at 30-40°C for 2-4 hours to obtain 2'-((5-(4-methylpiperazin-l-yl)pyridin-2-yl)amino)-7',8'-dihydro-6'H- spiro [cyclohexane- 1 ,9'-pyrazino[ 1 ',2' : 1 ,5]pyrrolo[2,3 -d]pyrimidin]-6'- onedihydrochlorideentahydrate (Trilaciclib dihydrochloride pentahydrate, 12.0 grams) having HPLC purity of >99.5%. Example 7: Preparation of 2^,-((5-(4-methylpiperazin-l-v^)pyridin-2-v^)amino)-7^,,8^,- dihydro-6^,H-spiro [cyclohexane- pyrazino [1 ’,2’ : 1,5] pyrrolo [2, 3-d] pyrimidin]-6^,-one

dihydrochloride pentahydrate (Trilaciclib dihydrochloride pentahydrate or THC16) [00108] To a mixture of tert-butyl 2'-((5-(4-methylpiperazin-l-yl)pyridin-2-yl)amino)-6'- oxo-6'H-spiro[cyclohexane-l,9'-pyrazino[T,2':l,5]pyrrolo[2,3-d]pyrimidine]-7'(8'H)- carboxylate (a compound of Formula IA, 0.4 grams) in methanol (14 ml) and water (6 ml), concentrated HC1 (3 ml) at 20-30°C was added and the reaction was heated to 50-60°C. After reaction completion, it was filtered through 0.2p filter paper and the filtrate was added into pre-cooled ethyl acetate (150 ml) and stirred for 2-3 hours at 0-5°C to obtain yellow colored suspension. Solid was filtered and dried at 30-40°C for 2-4 hours to afford 2'-((5-(4- methylpiperazin-1 -yl)pyri din-2 -yl)amino)-7',8'-dihydro-6'H-spiro[cy cl ohexane- 1,9'- pyrazino[l',2': l,5]pyrrolo[2,3-d]pyrimidin]-6'-onedihydrochloride pentahydrate (Trilaciclib dihydrochloride pentahydrate, 0.350 grams), having HPLC purity of >99.5%.

Example 8: Preparation of tert-butyl 2^,-chloro-6^,-oxo-6^,H-spiro[cvclohexane-l,9^,- pyrazino [ l',2': 1 ,5]pyrrolo[2,3-d]pyrimidine]-7'(8'H)-carboxylate (a compound of Formula IA)

[00109] Tert-butyl ((l-((5-bromo-2-chloropyrimidin-4-yl)amino)cyclohexyl)methyl) carbamate (a compound of Formula IV, 100 grams), prop-2-yn-l-ol (33.38 grams) and TBAF 3H2O (187.9 grams) were added to 2-methyl tetrahydrofuran (1200 ml) and the mixture was stirred for 20-30 minutes under nitrogen atmosphere. Pd(PPh3)2C12 (5.01 grams) was added, and the mixture was heated to 50-55°C. After completion of the reaction, the reaction mixture was cooled to 20-30°C and washed with water (250 ml x 2). Organic phase was distilled under vacuum to obtain oily residue of tert-butyl ((l-((2-chloro-5-(3- hydroxyprop-l-yn-l-yl)pyrimidin-4-yl)amino) cyclohexyl)methyl)carbamate (a compound of Formula V, 130.0g; purity > 84.0%).

[00110] 2-methyl tetrahydrofuran (1800 ml) and TBAF 3H2O (270.60 grams) were added to the oily residue, and the reaction mixture was heated to 70-78°C. After reaction completion, the mixture was cooled to 20-30°C and washed with water (1000 ml). Organic phase was distilled under vacuum to obtain about 150g of oily compound-tert-butyl ((l-(2- chloro-6-(hydroxymethyl)-7H-pyrrolo[2,3-d]pyrimidin-7-yl)cyclohexyl)methyl) carbamate (a compound of Formula VI) having purity of > 70.0% (HPLC).

[00111] The compound was dissolved in ethyl acetate (1000 ml) and water (100 ml) was added thereto. The reaction mixture was cooled to 10-20°C and bis(acetoxy)iodobenzene (BAIB) (245.6 grams) was added, followed by addition of a solution of (2, 2,6,6- tetramethylpiperidin-l-yl)oxidanyl (TEMPO) (14.89 grams) in ethyl acetate (200ml). The reaction temperature was raised to 20-30°C. After reaction completion, the organic layer was washed with saturated solution of sodium sulphite, sodium bicarbonate and sodium chloride solution. The organic layer was distilled off under vacuum to obtain brown oily colored residue (HPLC purity >75.0%). The residue was stirred with isopropanol to (200 ml) form slurry, and the slurry was filtered to obtain compound II A ( Purity: 96-97%). The resulting solid was dissolved in toluene (180 ml) with heating and cooled. The mixture was filtered to provide compound IIA having purity > 99% (HPLC) having an XRPD conforming to Figure 1.

[00112] Further aspects and embodiments of the present disclosure are presented in the numbered clauses below:

A process for preparation of a compound of Formula I,

wherein PG represents a protecting group, said process comprising: coupling a compound of Formula II with a compound of Formula III to obtain the compound of Formula I

The process according to clause 1, wherein the step of coupling the compound of Formula II with the compound of Formula III comprises reacting the compound of Formula II with the compound of Formula III in presence of a Pd catalyst to obtain the compound of Formula I. A process according to clause 1 or clause 2 wherein the coupling of the compound of Formula II with the compound of Formula III is carried out in the presence of a Pd catalyst selected from Pd(OAc)2/(±)BINAP, Pd(OAc)2/PPh3, Pd(PPh3)4, Pd(ddpf)C12 CH2CI2, and Pd(PPh3)2C12, and particularly Pd(OAc)2/(±)BINAP. A process according to any of clauses 1, 2 or 3 wherein the coupling of the compound of Formula II with the compound of Formula III is carried out in the presence of a base; optionally an inorganic base, an alkali metal base, or an alkaline earth metal base; more particularly an alkali metal base; optionally wherein the base is potassium carbonate, sodium carbonate, potassium bicarbonate, sodium bicarbonate, potassium tert-butoxide, sodium t-butoxide, cesium carbonate, and tripotassium phosphate, or mixtures thereof. A process according to any of clauses 1, 2, 3, or 4, wherein the coupling of the compound of Formula II with the compound of Formula III is carried out in the presence of a base selected from potassium carbonate, sodium carbonate, potassium bicarbonate, potassium tert-butoxide, cesium carbonate, and tripotassium phosphate, or mixtures thereof. A process according to any of clauses 1, 2, 3, 4, or 5, wherein the coupling of the compound of Formula II with the compound of Formula III is carried out in the presence of a base selected from potassium carbonate, tripotassium phosphate or mixtures thereof, and preferably potassium carbonate. A process according to any of clauses 1, 2, 3, 4, 5, or 6, wherein the coupling is carried out in a solvent, particularly wherein the solvent is selected from: cyclohexane, chloroform, toluene, xylene, ethylbenzene, diethyl ether, diisopropyl ether, methyl tert-butyl ether, ethyl acetate, isopropyl acetate, n-butyl acetate, methanol, ethanol, isopropanol, n-butanol, t-butanol, acetone, methyl ethyl ketone, methyl isobutyl ketone, methylene dichloride (MDC), 2-methyl tetrahydrofuran (2 -Me THF), tetrahydrofuran (THF), and 1,4-di oxane, and mixtures thereof. A process according to any of clauses 1, 2, 3, 4, 5, 6, or 7, wherein the coupling is carried out in a solvent selected from toluene, xylene, ethylbenzene, diethyl ether, diisopropyl ether, methyl tert-butyl ether, methylene dichloride (MDC), 2-methyl tetrahydrofuran (2 -Me THF), tetrahydrofuran (THF), and 1,4-di oxane, and mixtures thereof. A process according to any of clauses 1, 2, 3, 4, 5, 6, 7, or 8, wherein the coupling is carried out in a solvent selected from toluene, xylene, or ethylbenzene, and preferably toluene. A process according to any of clauses 1, 2, 3, 4, 5, 6, 7, 8, or 9, wherein the coupling is carried out under heating, preferably at a temperature of: 50°C to 120°C, 60°C to

110°C, or 70°C to 105°C, or 80°C to 100°C, particularly 80°C to 100°C or 85°C to 95°C. A process according to any of clauses 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10, wherein the coupling is carried out under an inert atmosphere, preferably under nitrogen or argon, particularly nitrogen. A process according to any of clauses 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or 11, wherein the compound of Formula I is treated with a metal scavenger, preferably selected from: N-acetylcysteine, a silica supported metal scavenger (particularly a thiol-derivatized silica gel, a triamine-derivatized silica gel, a (R)-cysteine-derivatized silica gel, a triaminetetraacetic acid-derivatized silica gel, a triaminetetraacetic acid- derivatized silica gel, a sodium salt-derivatized silica gel, a 2,4,6-trimercaptotriazine-derivatized silica gel, or a propylsulphonic acid-derivatized silica gel), polyamine resin, macroporous polystyrene-2,4,6- trimercaptotriazine (MP-TMT), SP-TMT, ammonium pyrrolidinedithiocarbamate (APTDC), or an isopropyl xanthate salt, and mixtures thereof; or where the metal scavenger is selected from: N-acetylcysteine, a silica supported metal scavenger (particularly a thiol-derivatized silica gel, a triamine- derivatized silica gel, a (R)-cysteine-derivatized silica gel, a triaminetetraacetic acid- derivatized silica gel, a triaminetetraacetic acid- derivatized silica gel, a sodium salt- derivatized silica gel, a 2,4,6-trimercaptotriazine-derivatized silica gel, or a propylsulphonic acid-derivatized silica gel), polyamine resin, macroporous polystyrene-2,4,6- trimercaptotriazine (MP-TMT), microporous polystyrene-2,4,6- trimercaptotriazine, semiporous polystyrene-2,4,6- trimercaptotriazine (SP-TMT), ammonium pyrrolidinedithiocarbamate (APTDC), or an isopropyl xanthate salt, and mixtures thereof; or wherein the metal scavenger is selected from: N-acetylcysteine, a silica supported metal scavenger (particularly a thiol-derivatized silica gel, a triamine- derivatized silica gel, a (R)-cysteine-derivatized silica gel, a triaminetetraacetic acid- derivatized silica gel, a triaminetetraacetic acid- derivatized silica gel, a sodium salt- derivatized silica gel, a 2,4,6-trimercaptotriazine-derivatized silica gel, or a propylsulphonic acid-derivatized silica gel), polyamine resin, microporous polystyrene-2,4,6- trimercaptotriazine, semiporous polystyrene-2,4,6- trimercaptotriazine (SP-TMT), ammonium pyrrolidinedithiocarbamate (APTDC), or an isopropyl xanthate salt, and mixtures thereof; or particularly wherein the metal scavenger is thiol-derivatized silica gel and/or N-acetylcysteine, and most preferably N-acetylcysteine. A process according to any of clauses 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12, wherein the compound of Formula I is isolated from the reaction mixture by a process comprising (i) filtration, (ii) combining the filtrate with a base (preferably a base as defined in any of clauses 4 to 6), and optionally a metal scavenger (preferably a metal scavenger as defined in clause 12, (iii) stirring the mixture in step (ii), preferably at a temperature of 30°C to 80°C, 40°C to 70°C, 50°C to 60°C, optionally for 30 minutes to 8 hours, 1 hour to 6 hours, 2 hours to about 4 hours, or about 2.5 hours; and (iv) isolating the compound of Formula I by centrifuge, decantation or filtration, preferably by filtration. A process according to clause 13, wherein the compound of Formula I is isolated by filtration, and optionally washing, to obtain the compound of Formula I. A process according to any of clauses 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, or 14, wherein the step of coupling the compound of Formula II with the compound of Formula III comprises: (a) mixing the compound of Formula II with the compound of Formula III, a Pd catalyst, an inorganic base and a solvent under an inert atmosphere to form a reaction mixture; (b) stirring the reaction mixture at a temperature ranging from about 25°C to about 35°C; (c) heating the stirred reaction mixture to a temperature ranging from about 80°C to about 100°C to completion of the reaction; and (d) quenching the reaction mixture by: cooling the reaction mixture to a temperature ranging from about 50°C to about 60°C and effecting addition of a metal scavenger (preferably as defined in clause 12) and water to obtain a crude product mixture having the compound of Formula I. A process according to any of clauses 12, 13, 14, or 15, wherein the metal scavenger in step (ii) is used, and wherein the metal scavenger is N-acetyl cysteine. A process of any one of the clauses 1 and 2, or any of clauses 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16, wherein the process further comprises a step of purifying the compound of Formula I to obtain a substantially pure compound of Formula I, the step of purifying comprises: (a) mixing the compound of Formula I with a first metal scavenger in presence of a solvent to obtain a mixture;

(b) exposing the mixture to an elevated temperature under stirring conditions;

(c) effecting filtration of the mixture to obtain the filtrate;

(d) mixing the filtrate with a second metal scavenger in presence of an aqueous solution of a base to obtain a second mixture; and

(e) effecting filtration of the second mixture to obtain the substantially pure compound of Formula I. A process according to any of clauses 12, 13, 14, 15, 16, or 17, , wherein the first metal scavenger and second metal scavenger are same or different and selected independently from: N-acetyl cysteine, a polyamine resin, a silica supported metal scavenger, an isopropyl xanthate salt, ammonium pyrrolidinedithiocarbamate, and mixtures thereof; preferably selected independently from: N-acetylcysteine, a silica supported metal scavenger (particularly a thiol-derivatized silica gel, a triamine- derivatized silica gel, a (R)-cysteine-derivatized silica gel, a triaminetetraacetic acid- derivatized silica gel, a triaminetetraacetic acid- derivatized silica gel, a sodium salt- derivatized silica gel, a 2,4,6-trimercaptotriazine-derivatized silica gel, or a propyl sulphonic acid-derivatized silica gel), polyamine resin, macroporous polystyrene-2,4,6- trimercaptotriazine (MP-TMT), SP-TMT, ammonium pyrrolidinedithiocarbamate (APTDC), or an isopropyl xanthate salt, and mixtures thereof. A process according to clause 18, wherein the first and second metal scavengers are different and are selected from N-acetylcysteine and a thiol-derivatized silica gel. A process according to any of clauses 17, 18, or 19, wherein the solvent comprises toluene, and any or a combination of DMSO and DMF; preferably wherein the solvent comprises toluene and DMSO, or toluene and DMF. A process according to any of clauses 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20, wherein the compound of Formula II is obtained by reacting a compound of Formula IV with prop-2-yn-l-ol

Formula IV wherein PG represents the protecting group.

A process according to clause 21, wherein the step of obtaining the compound of Formula II comprises:

(b) effecting cyclization of a compound of Formula V to obtain a compound of

Formula VI

(c) effecting oxidative cyclization of a compound of Formula VI to obtain a compound of Formula II

Formula VI Formula II A process according to clause 22, wherein the step of effecting oxidative cyclization of a compound of Formula VI comprises exposing the compound of Formula VI to an elevated temperature in presence of an oxidant. A process according to clause 23, wherein the oxidant is selected from: Oxone/NaCl, NaOCl/TEMPO, MnO2/Oxone/Na2CO3, MnO2/Oxone/NaHCO3, 2-Iodoxy benzoic acid (IDB), Eaton’s reagent, 2-Iodoxy benzoic acid (IDB)/TEMPO, hydrogen peroxide, Bis(acetoxy)iodobenzene (BAIB)/TEMPO or mixtures thereof; preferably where the oxidant is BAIB/TEMPO. A process according to any of clauses 22, 23 or 24, wherein step (c) is carried out in a solvent selected from the group consisting of: water, cyclohexane, chloroform, toluene, xylene, ethylbenzene, diethyl ether, diisopropyl ether, methyl tert-butyl ether, ethyl acetate, isopropyl acetate, n-butyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, N- methyl-2-pyrrolidone, methylene dichloride (MDC), 2-methyl tetrahydrofuran (2 -Me THF), tetrahydrofuran, and 1,4-di oxane, and mixtures thereof. A process according to any of clauses 22, 23, 24, or 25, wherein step (c) is carried out in a solvent selected from the group consisting of: water, cyclohexane, chloroform, toluene, xylene, ethylbenzene, diethyl ether, diisopropyl ether, methyl tert-butyl ether, ethyl acetate, isopropyl acetate, n-butyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, methylene dichloride (MDC), 2-methyl tetrahydrofuran (2 -Me THF), tetrahydrofuran, or mixtures thereof. A process according to any of clauses 22, 23, 24, 25, or 26, wherein step (c) is carried out in a solvent selected from the group consisting of: water, diethyl ether, diisopropyl ether, methyl tert-butyl ether, ethyl acetate, isopropyl acetate, and n-butyl acetate; preferably wherein step (c) is carried out in a solvent selected from the group consisting of: water, ethyl acetate, isopropyl acetate, and n-butyl acetate, or mixtures thereof. A process according to any of clauses 22, 23, 24, 25, 26, or 27, wherein step (c) is carried out in a solvent selected from the group consisting of: water, ethyl acetate, isopropyl acetate, and n-butyl acetate; preferably wherein step (c) is carried out in a solvent selected from a mixture comprising water, and one or more of ethyl acetate, isopropyl acetate, and n-butyl acetate; and more preferably wherein step (c) is carried out in a mixture of water and ethylacetate. A process according to any of clauses 22, 23, 24, 25, 26, 27, or 28, wherein step (c) is carried out in the absence of an acid. A process according to any of clauses 22, 23, 24, 25, 26, 27, 28, or 29, wherein step (c) is carried out at a temperature of: 15°C to 50°C, 18°C to 45°C, 20°C to 40°C, or 20°C to 30°C. A process according to any of clauses 22, 23, 24, 25, 26, 27, 28, 29, or 30, wherein step (a) is carried out in the presence of TBAF. A process according to any of clauses 22, 23, 24, 25, 26, 27, 28, 29, 30, or 31, wherein the step of cyclization of a compound of Formula V is effected in presence of tetra-n-butylammonium fluoride (TBAF) and a solvent. A process according to any of clauses 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, or 32, wherein step (b) is carried out in a solvent selected from the group consisting of: water, cyclohexane, chloroform, toluene, xylene, ethylbenzene, diethyl ether, diisopropyl ether, methyl tert-butyl ether, ethyl acetate, isopropyl acetate, n-butyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, methylene dichloride (MDC), 2-methyl tetrahydrofuran (2 -Me THF), tetrahydrofuran, or mixtures thereof; preferably wherein step (b) is carried out in a solvent selected from the group consisting of: chloroform, diethyl ether, diisopropyl ether, methyl tert-butyl ether, ethyl acetate, isopropyl acetate, n-butyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, methylene dichloride, 2-methyl tetrahydrofuran (2 -Me THF), and tetrahydrofuran, or mixtures thereof. A process according to any of clauses 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, or 33, wherein step (b) is carried out in a solvent selected from the group consisting of: diethyl ether, diisopropyl ether, methyl tert-butyl ether, 2-methyl tetrahydrofuran (2- Me THF), and tetrahydrofuran, or mixtures thereof; and preferably wherein step (b) is carried out in a solvent selected from the group consisting of: 2-methyl tetrahydrofuran and tetrahydrofuran, or mixtures thereof; and more preferably wherein step (b) is carried out in tetrahydrofuran. A process according to any of clauses 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, or

34, wherein step (b) is carried out at a temperature of: 40°C to 100°C, 50°C to 95°C, 60°C to 90°C, 65°C to 85°C, or 70°C to 80°C. A process according to any of clauses 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, or 35, wherein step (b) comprises: (i) mixing the compound of Formula V with TBAF in presence of a solvent to obtain a reaction mixture; and (b) heating the reaction mixture at a temperature ranging from about 60°C to about 80°C to obtain the compound of Formula VI. A process according to any of clauses 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34,

35, or 36, wherein the compound of Formula VI is directly subjected to the step of oxidative cyclization without any intermittent purification step or wherein the compound of Formula VI is purified before subjecting to the step of cyclization. A process according to any of clauses 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, or 37, wherein the compound of Formula VI is directly subjected to the step of oxidative cyclization without any intermittent purification step. A process according to any of clauses 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, or 38, wherein the compound of Formula V.is isolated by distillation or evaporation, and directly subjected to oxidative cyclization without purification. A process according to any of clauses 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 35, 37, 38, or 39, wherein the Pd based catalyst in step (a) is selected from Pd(OAc)₂/(±)BINAP, Pd(OAc)2/PPh₃, Pd(PPh₃)₄, Pd(ddpf)Cl₂ CH2CI2, and Pd(PPh₃)2C12; and preferably Pd(PPh₃)2C12. A process according to any of clauses 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, or 40, wherein step (a) is carried out in a solvent selected from the group consisting of: water, cyclohexane, chloroform, toluene, xylene, ethylbenzene, diethyl ether, diisopropyl ether, methyl tert-butyl ether, ethyl acetate, isopropyl acetate, n-butyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, methylene dichloride (MDC), 2-methyl tetrahydrofuran (2 -Me THF), tetrahydrofuran, or mixtures thereof; preferably wherein step (b) is carried out in a solvent selected from the group consisting of: chloroform, diethyl ether, diisopropyl ether, methyl tertbutyl ether, ethyl acetate, isopropyl acetate, n-butyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, methylene dichloride, 2-methyl tetrahydrofuran (2 -Me THF), and tetrahydrofuran, or mixtures thereof. A process according to any of clauses 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, or 41, wherein step (a) is carried out in a solvent selected from the group consisting of: diethyl ether, diisopropyl ether, methyl tert-butyl ether, 2- methyl tetrahydrofuran (2 -Me THF), and tetrahydrofuran, or mixtures thereof; and preferably wherein step (a) is carried out in a solvent selected from the group consisting of: 2-methyl tetrahydrofuran and tetrahydrofuran, or mixtures thereof; and more preferably wherein step (b) is carried out in 2-methyl tetrahydrofuran. A process according to any of clauses 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, or 42, wherein step (a) is carried out at a temperature of: 40°C to 80°C, 40°C to 70°C, 45°C to 65°C, 45°C to 60°C, or 50°C to 55°C. A process according to any of clauses 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, or 43, wherein step (a) is carried out in an inert atmosphere, preferably under nitrogen or argon, and more preferably under nitrogen. A process according to any of clauses 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, or 44, wherein step (a) comprises: (i) mixing the compound of Formula IV, prop-2-yn-l-ol and TBAF in presence of the solvent under an inert atmosphere; (b) effecting addition of the Pd based catalyst to obtain a reaction mixture; and (c) heating the reaction mixture at a temperature of about 50°C to about 70°C to obtain the compound of Formula V. A process according to any of clauses 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, or 45, wherein the compound of Formula V is directly subjected to the step of cyclization either after purification, or without any intermittent purification step. A process according to any of clauses 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, or 46, wherein the compound of Formula V.is isolated by distillation or evaporation, and directly subjected to cyclization without purification. The process of any one of the preceding clauses, wherein PG is a protecting group selected from t-butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, carbamate group, alkyl group, aryl group, allyl group, and aryl alkyl group. A process according to any of clauses 1 to 47, wherein PG is a protecting group selected from t-butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, carboxylic ester group [-C(=O)-OR, wherein R is alkyl or aryl as defined herein], alkyl group, aryl group, allyl group, and aryl alkyl group. A process according to any preceding clause, wherein PG is a protecting group selected from t-butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, alkyl group, aryl group, allyl group, and aryl alkyl group. A process according to any one of the preceding clauses, wherein PG is a t- butyloxycarbonyl (BOC) group. A process according to any preceding clause, further comprising converting the compound of Formula I into trilaciclib or a pharmaceutically acceptable salt of trilaciclib, preferably wherein the pharmaceutically acceptable salt of trilaciclib is trilaciclib citrate, trilaciclib hemicitrate, or trilaciclib dihydrochloride. A process according to any preceding clause, further comprising converting the compound of Formula I into a pharmaceutically acceptable salt of trilaciclib, preferably wherein the pharmaceutically acceptable salt of trilaciclib is trilaciclib citrate, trilaciclib hemicitrate, trilaciclib dihydrochloride, or trilaciclib dihydrochloride pentahydrate. A process according to clause 53, comprising converting the compound of Formula I into trilaciclib and converting the trilaciclib into a pharmaceutically acceptable salt of trilaciclib, preferably trilaciclib citrate, trilaciclib hemicitrate, trilaciclib dihydrochloride, or trilaciclib dihydrochloride pentahydrate. A process according to clause 53, comprising converting the compound of Formula I into a pharmaceutically acceptable salt of trilaciclib, preferably trilaciclib citrate, trilaciclib hemicitrate, trilaciclib dihydrochloride, or trilaciclib dihydrochloride pentahydrate, preferably by reaction of the compound of Formula I with an acid to form the pharmaceutically acceptable salt. A process according to clause 55, comprising reaction of the compound of Formula I with citric acid or hydrochloric acid to form trilaciclib citrate, trilaciclib hemicitrate, trilaciclib dihydrochloride, or trilaciclib dihydrochloride pentahydrate. A process according to any of clauses 52, 53, 54, 55, or 56, further comprising combining the trilaciclib or pharmaceutically acceptable salt of trilaciclib, preferably wherein the pharmaceutically acceptable salt of trilaciclib is trilaciclib citrate, trilaciclib hemicitrate, trilaciclib dihydrochloride, or trilaciclib dihydrochloride pentahydrate, with at least one pharmaceutically acceptable excipient to form pharmaceutical composition or dosage form. A compound of formula V

Formula V wherein PG represents a protecting group selected from t-butyloxy carbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, carbamate group, alkyl group, aryl group, allyl group, and aryl alkyl group. A compound according to clause 58, wherein PG represents t-butyloxycarbonyl (BOC) group. A compound of formula VI

Formula VI wherein PG represents a protecting group selected from t-butyloxy carbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, carbamate group, alkyl group, aryl group, allyl group, and aryl alkyl group. A compound according to clause 60, wherein PG represents t-butyloxy carbonyl (BOC) protecting group. A compound of formula I

Formula I wherein PG represents a protecting group selected from t-butyloxy carbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, carbamate group, alkyl group, aryl group, allyl group, and aryl alkyl group. A compound according to clause 62, wherein PG represents t-butyloxy carbonyl (BOC) group. A crystalline form of a compound of Formula IA

Formula IA wherein the crystalline form has X-ray powder diffraction pattern comprising peaks at 5.8, 12.3, 13.8, 16.3, 19.3, 24.6 and 25.4 deg-2-theta ± 0.2 deg-2-theta. A crystalline form of a compound of Formula IIA,

Formula IIA wherein the crystalline form has X-ray powder diffraction pattern comprising peaks at 5.9, 9.6, 12.5, 17.2, 24.1, 25.0, 25.9 and 26.8 deg-2-theta ± 0.2 deg-2-theta. Use of compound of formula I for manufacture of trilaciclib, pharmaceutically acceptable salt or derivative thereof

Formula I wherein PG represents a protecting group selected from t-butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, carbamate group, alkyl group, aryl group, allyl group, and aryl alkyl group. Use according to clause 66, wherein PG represents t-butyloxycarbonyl (BOC) group. Use of compound of formula V for manufacture of trilaciclib or pharmaceutically acceptable salt thereof

wherein PG represents a protecting group selected from t-butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, carbamate group, alkyl group, aryl group, allyl group, and aryl alkyl group. Use according to clause 68, wherein PG represents t-butyloxycarbonyl (BOC) group. Use of compound of formula VI for manufacture of trilaciclib or pharmaceutically acceptable salt thereof

wherein PG represents a protecting group selected from t-butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, carbamate group, alkyl group, aryl group, allyl group, and aryl alkyl group. Use according to clause 70, wherein PG represents t-butyloxycarbonyl (BOC) group. Use of crystalline form of a compound of Formula IA, preferably as defined in clause

64, for manufacture of trilaciclib, pharmaceutically acceptable salt or derivative thereof

Formula IA Use of crystalline form of a compound of Formula IIA, preferably as defined in clause 65, for manufacture of trilaciclib, pharmaceutically acceptable salt or derivative thereof

Formula HA

Claims

1. A process for preparation of a compound of Formula I,

2. The process of claim 1, wherein the step of coupling the compound of Formula II with the compound of Formula III comprises reacting the compound of Formula II with the compound of Formula III in presence of a Pd catalyst to obtain the compound of Formula I.

3. The process of any one of the claims 1 and 2, wherein the process further comprises a step of purifying the compound of Formula I to obtain a substantially pure compound of Formula I, the step of purifying comprises:

(a) mixing the compound of Formula I with a first metal scavenger in presence of a solvent to obtain a mixture;

(b) exposing the mixture to an elevated temperature under stirring conditions;

(c) effecting filtration of the mixture to obtain the filtrate;

(e) effecting filtration of the second mixture to obtain the substantially pure compound of Formula I. The process of claim 3, wherein the first metal scavenger and second metal scavenger are same or different and selected independently from: n-acetyl cysteine, a polyamine resin, a silica supported metal scavenger, an isopropyl xanthate salt, ammonium pyrrolidinedithiocarbamate, and mixtures thereof. The process of claim 3, wherein the solvent comprises toluene, and any or a combination of DMSO and DMF. The process of claim 1, wherein the compound of Formula II is obtained by reacting a compound of Formula IV with prop-2-yn-l-ol

Formula IV ^PG wherein PG represents the protecting group. The process of claim 6, wherein the step of obtaining the compound of Formula II comprises:

Formula IV PG Formula V

(b) effecting cyclization of a compound of Formula V to obtain a compound of

Formula VI

The process of claim 7, wherein the step of effecting oxidative cyclization of a compound of Formula VI comprises exposing the compound of Formula VI to an elevated temperature in presence of an oxidant. The process of claim 8, wherein the oxidant is selected from: Oxone/NaCl, NaOCl/TEMPO, MnO2/Oxone/Na2CO3, MnO2/Oxone/NaHCO3, 2-Iodoxy benzoic acid (IDB), Eaton’s reagent, 2-Iodoxy benzoic acid (IDB)/TEMPO, hydrogen peroxide, Bis(acetoxy)iodobenzene (BAIB)/TEMPO or mixtures thereof. The process of claim 7, wherein the step of cyclization of a compound of Formula V is effected in presence of tetra-n-butyl ammonium fluoride (TBAF) and a solvent. The process of any one of the preceding claims, wherein PG represents a protecting group selected from t-butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, carbamate group, alkyl group, aryl group, allyl group, and aryl alkyl group; or wherein PG represents a protecting group selected from t-butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, carboxylic ester group [-C(=O)-OR, wherein R is alkyl or aryl as defined herein], alkyl group, aryl group, allyl group, and aryl alkyl group; or alternatively wherein PG represents a protecting group selected from t- butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, alkyl group, aryl group, allyl group, and aryl alkyl group.

The process of any one of the preceding claims, wherein PG represents t- butyloxycarbonyl (BOC) group.

A compound of formula V

Formula V wherein PG represents a protecting group selected from t-butyloxy carbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, carbamate group, alkyl group, aryl group, allyl group, and aryl alkyl group; or wherein PG represents a protecting group selected from t-butyloxy carbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, carboxylic ester group [-C(=O)-OR, wherein R is alkyl or aryl as defined herein], alkyl group, aryl group, allyl group, and aryl alkyl group; or alternatively wherein PG represents a protecting group selected from t-butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, alkyl group, aryl group, allyl group, and aryl alkyl group.

The compound of claim 13, wherein PG represents t-butyloxycarbonyl (BOC) group.

A compound of formula VI

Formula VI wherein PG represents a protecting group selected from t-butyloxy carbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, carbamate group, alkyl group, aryl group, allyl group, and aryl alkyl group; or wherein PG represents a protecting group selected from t-butyloxy carbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, carboxylic ester group [-C(=O)-OR, wherein R is alkyl or aryl as defined herein], alkyl group, aryl group, allyl group, and aryl alkyl group; or alternatively wherein PG represents a protecting group selected from t-butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, alkyl group, aryl group, allyl group, and aryl alkyl group. The compound of claim 15, wherein PG represents t-butyloxycarbonyl (BOC) protecting group. A compound of formula I

Formula I wherein PG represents a protecting group selected from t-butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, carbamate group, alkyl group, aryl group, allyl group, and aryl alkyl group; or wherein PG represents a protecting group selected from t-butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, carboxylic ester group [-C(=O)-OR, wherein R is alkyl or aryl as defined herein], alkyl group, aryl group, allyl group, and aryl alkyl group; or alternatively wherein PG represents a protecting group selected from t-butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, alkyl group, aryl group, allyl group, and aryl alkyl group. The compound of claim 17, wherein PG represents t-butyloxycarbonyl (BOC) group. A crystalline form of a compound of Formula IA

Boc

Formula I wherein PG represents a protecting group selected from t-butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, carbamate group, alkyl group, aryl group, allyl group, and aryl alkyl group; or wherein PG represents a protecting group selected from t-butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, carboxylic ester group [-C(=O)-OR, wherein R is alkyl or aryl as defined herein], alkyl group, aryl group, allyl group, and aryl alkyl group; or alternatively wherein PG represents a protecting group selected from t-butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, alkyl group, aryl group, allyl group, and aryl alkyl group. The compound of claim 21, wherein PG represents t-butyloxy carbonyl (BOC) group.

Use of compound of formula V for manufacture of trilaciclib or pharmaceutically acceptable salt thereof

The compound of claim 23, wherein PG represents t-butyloxycarbonyl (BOC) group.

Use of compound of formula VI for manufacture of trilaciclib or pharmaceutically acceptable salt thereof

Formula VI wherein PG represents a protecting group selected from t-butyloxy carbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, carbamate group, alkyl group, aryl group, allyl group, and aryl alkyl group; or wherein PG represents a protecting group selected from t-butyloxy carbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, carboxylic ester group [-C(=O)-OR, wherein R is alkyl or aryl as defined herein], alkyl group, aryl group, allyl group, and aryl alkyl group; or alternatively wherein PG represents a protecting group selected from t-butyloxycarbonyl (BOC) group, fluorenylmethyloxycarbonyl (FMOC) group, carboxybenzyl (CBz) group, alkyl group, aryl group, allyl group, and aryl alkyl group. The compound of claim 25, wherein PG represents t-butyloxycarbonyl (BOC) group. Use of crystalline form of a compound of Formula IA for manufacture of trilaciclib, pharmaceutically acceptable salt or derivative thereof

Use of crystalline form of a compound of Formula IIA for manufacture of trilaciclib, pharmaceutically acceptable salt or derivative thereof

Formula HA