HK1249096B - Ethynyl derivatives - Google Patents

Description

Ethylene derivatives

Technical Field

The present invention relates to ethynyl derivatives of formula I

in

^R1 is hydrogen or F;

n is 1 or 2

Or it relates to a pharmaceutically acceptable acid addition salt thereof.

Preferred compounds are those wherein (R ¹ ) _n is hydrogen, 3-fluoro, 4-fluoro or 2,5-difluoro.

It has now been surprisingly discovered that compounds of the general formula I are metabotropic glutamate receptor antagonists (NAMs = negative allosteric modulators). Compounds with a similar main body core have generally been described as positive allosteric modulators of the mGluR5 receptor. Surprisingly, it has been found that highly potent mGluR5 antagonists are obtained rather than mGluR5 positive allosteric modulators, which have a completely opposite pharmacology compared to positive allosteric modulators.

In the presence of a fixed concentration of glutamate, mGluR5 positive allosteric modulators (PAMs) lead to increased receptor activity (Ca2 ⁺ mobilization), whereas allosteric antagonists (negative allosteric modulators, NAMs) lead to a decrease in receptor activation.

The compounds of formula I are distinguished by having valuable therapeutic properties. They can be used to treat anxiety and pain, depression, Fragile-X syndrome, autism spectrum disorders, Parkinson's disease, and gastroesophageal reflux disease (GERD).

Background Art

In the central nervous system (CNS), stimuli are transmitted through the interaction of neurotransmitters emitted by neurons with neuroreceptors.

Glutamate is the main excitatory neurotransmitter in the brain and plays a unique role in a variety of central nervous system (CNS) functions. Glutamate-dependent stimulatory receptors are divided into two main categories. The first main category, ionotropic receptors, form ligand-controlled ion channels. Metabotropic glutamate receptors (mGluRs) belong to the second main category and also belong to the family of G-protein coupled receptors.

Currently, eight different members of these mGluRs are known, and some of these members even have subtypes. Based on their sequence homology, signal transduction mechanism, and agonist selectivity, these eight receptors can be subdivided into three subgroups:

mGluR1 and mGluR5 belong to group I, mGluR2 and mGluR3 belong to group II, and mGluR4, mGluR6, mGluR7, and mGluR8 belong to group III.

Negative allosteric modulators of metabotropic glutamate receptors belonging to the first group can be used to treat or prevent acute and/or chronic neurological disorders, such as Parkinson's disease, fragile X syndrome, autistic disorders, cognitive disorders and memory deficits, as well as chronic and acute pain and gastroesophageal reflux disease (GERD).

Other treatable indications in this regard are limited brain function caused by bypass surgery or transplantation, poor cerebral blood supply, spinal cord injury, head injury, hypoxia caused by pregnancy, cardiac arrest and hypoglycemia. Additional treatable indications are ischemia, Huntington's chorea, amyotrophic lateral sclerosis (ALS), dementia caused by AIDS, eye damage, retinopathy, idiopathic parkinsonism or drug-induced parkinsonism and conditions that lead to glutamate deficiency, such as, for example, muscle spasms, convulsions, migraines, urinary incontinence, nicotine addiction, opiate addiction, anxiety, vomiting, dyskinesia and depression.

Disorders that are fully or partially mediated by mGluR5 are, for example, acute, traumatic and chronic degenerative processes of the nervous system, such as Alzheimer's disease, senile dementia, Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis and multiple sclerosis, psychiatric disorders such as schizophrenia and anxiety disorders, depression, pain and drug dependence (Expert Opin. Ther. Patents (2002), 12, (12)).

Selective mGluR5 antagonists are particularly useful for treating conditions requiring reduced activation of the mGluR5 receptor, such as anxiety and pain, depression, fragile X syndrome, autism spectrum disorders, Parkinson's disease, and gastroesophageal reflux disease (GERD).

Summary of the Invention

The present invention relates to compounds of formula I and pharmaceutically acceptable salts thereof, as pharmaceutically active compounds and their preparation. Further objects of the present invention are medicaments based on the compounds according to the invention and their preparation, as well as the use of said compounds in controlling or preventing mGluR5 receptor (NAM)-mediated conditions, such as anxiety and pain, depression, fragile X syndrome, autism spectrum disorders, Parkinson's disease and gastroesophageal reflux disease (GERD), and their use for the preparation of the corresponding medicaments.

The compounds of the present invention have been generally described in document 1 (WO2011128279) as positive allosteric modulators of the mGluR5 receptor. The most similar exemplary compounds are attached to a 5- or 6-membered ring. Surprisingly, it has been found that compounds with smaller ring sizes (4-membered rings) and with the absolute stereochemistry of the bicyclic ring (1R, 5S) are highly effective mGluR5 antagonists, which have a pharmacology completely opposite to that described for positive allosteric modulators in WO2011128279.

One embodiment of the present invention is a compound of formula I, for example the following:

(1S,5R)-2-Methyl-4-(5-(phenylethynyl)pyridin-2-yl)-2,4-diazabicyclo[3.2.0]heptan-3-one

(1R,5S)-2-(5-((4-Fluorophenyl)ethynyl)pyridin-2-yl)-4-methyl-2,4-diazabicyclo[3.2.0]heptan-3-one

(1R,5S)-2-(5-((3-fluorophenyl)ethynyl)pyridin-2-yl)-4-methyl-2,4-diazabicyclo[3.2.0]heptan-3-one or

(1R,5S)-2-(5-((2,5-difluorophenyl)ethynyl)pyridin-2-yl)-4-methyl-2,4-diazabicyclo[3.2.0]heptan-3-one.

BRIEF DESCRIPTION OF THE DRAWINGS

The main difference between positive and negative allosteric modulators can be seen in Figure 1. In the presence of a fixed concentration of glutamate, mGluR5 positive allosteric modulators (PAMs) lead to increased receptor activity (Ca ²⁺ mobilization), while allosteric antagonists (negative allosteric modulators, NAMs) lead to a reduction in receptor activation. The receptor affinities in Figure 1 are approximately 10 ^-7 M for PAMs and between 10 ^-7 M and 10 ^-8 M for NAMs. These values can also be measured using a binding assay instead of a radioligand (=MPEP), see assay description.

Figure 1 : Comparison of mGluR5 positive allosteric modulators (PAMs) and mGluR5 antagonists (negative allosteric modulators = NAMs)

The indications that can be addressed by the compounds are different. mGluR5-NAM is beneficial for indications that require reduction of excessive receptor activity, such as anxiety, pain, fragile X chromosome, autism spectrum disorder and gastroesophageal reflux disease. On the other hand, mGluR5 PAM can be used for indications that require normalization of reduced receptor activity, such as psychosis, epilepsy, schizophrenia, Alzheimer's disease and related cognitive impairment, and tuberous sclerosis.

This difference can actually be shown in anxiety animal models, such as the rat Vogel conflict drinking test, where the compound of Example 1 showed anxiolytic activity at a minimum effective dose of 0.1 mg/Kg, while mGluR-PAM was not considered to show activity in this animal model (see Figure 2).

Figure 2 : Activity of compound "Example 2" in the Vogel conflict drinking test in rats.

DETAILED DESCRIPTION

Biological Assays and Data:

Intracellular Ca2 ⁺ mobilization assay

A monoclonal HEK-293 cell line stably transfected with a cDNA encoding the human mGlu5a receptor was generated; for work with mGlu5a positive allosteric modulators (PAMs), a cell line with low receptor expression levels and low constitutive receptor activity was selected to allow differentiation of agonist activity from PAM activity. Cells were cultured in high glucose Dulbecco's Modified Eagle Medium (Dulbecco's Modified Eagle Medium) supplemented with 1 mM glutamine, 10% (vol/vol) heat-inactivated calf serum, penicillin/streptomycin, 50 μg/ml hygromycin, and 15 μg/ml blasticidin according to standard protocols (Freshney, 2000). All cell culture reagents and antibiotics were obtained from Invitrogen, Basel, Switzerland.

Approximately 24 hours before the experiment, ^5x104 cells/well were seeded in a poly-D-lysine-coated black/clear-bottom 96-well plate. Cells were loaded with 2.5 μM Fluo-4 AM in loading buffer (1xHBSS, 20 mM HEPES) at 37°C for 1 hour and washed five times with loading buffer. Cells were transferred to a Functional Drug Screening System 7000 (Hamamatsu, Paris, France), and 11 half-log serial dilutions of the test compound were added at 37°C. The cells were incubated for 10-30 minutes, and fluorescence was recorded online. After this pre-incubation step, the agonist L-glutamate was added to the cells at a concentration corresponding to the _EC20 (typically approximately 80 μM), and fluorescence was recorded online. To account for day-to-day changes in cellular responsiveness, the _EC20 of glutamate was determined by recording a full dose-response curve for glutamate immediately before each experiment.

The response is measured as the peak increment of fluorescence minus baseline (i.e., without the addition of L-glutamic acid), normalized to the maximum stimulation effect obtained with saturating concentrations of L-glutamic acid. XLfit is used to map % maximum stimulation, and XLfit is a curve fitting program that uses Levenburg Marquardt algorithm to iteratively map data. The single site competition analysis equation used is y=A+((B-A)/(1+((x/C)D))), where y is % maximum stimulation effect, A is minimum y, B is maximum y, C is _EC50 , and x is the log10 of the concentration of the competitive compound, and D is the slope of the curve (Hill coefficient (Hill Coefficient)). From these curves, _EC50 (concentration to achieve half maximum stimulation), Hill coefficient, and the maximum response represented by % of the maximum stimulation effect obtained with saturating concentrations of L-glutamic acid are calculated.

A positive signal obtained during pre-incubation with a PAM test compound (i.e., before applying an EC ₂₀ concentration of L-glutamate) indicates agonist activity, while a lack of this signal demonstrates a lack of agonist activity. A decrease in the signal observed after adding an EC ₂₀ concentration of L-glutamate indicates inhibitory activity of the test compound.

The corresponding results for compounds all having _EC50 values less than or equal to 100 nM are shown in the table of the following Examples.

WO2011128279 = Document 1

MPEP binding assay:

For binding experiments, cDNA encoding the human mGlu 5a receptor was transiently transfected into EBNA cells using the procedure described by Schlaeger and Christensen [Cytotechnology 15: 1-13 (1998)]. Cell membrane homogenates were stored at -80°C until the day of the assay, when they were thawed and resuspended and polytronised in 15 mM Tris-HCl, 120 mM NaCl, 100 mM KCl, 25 mM CaCl ₂ , 25 mM MgCl ₂ binding buffer, pH 7.4, to a final assay concentration of 20 μg protein/well.

Saturation isotherms were determined by adding twelve [ ³ H]MPEP concentrations (0.04-100 nM) to the membranes (in a total volume of 200 μl) for 1 h at 4° C. Competition experiments were performed with a fixed concentration of [ ³ H]MPEP (2 nM), and IC ₅₀ values of the test compounds were evaluated using 11 concentrations (0.3-10000 nM). Incubation was performed at 4° C. for 1 h.

At the end of the incubation, the membrane was filtered onto a unifilter (96-well white microplate with GF/C-bound filters pre-incubated for 1 h in 0.1% PEI in wash buffer, Packard BioScience, Meriden, CT) with a Filtermate 96 collector (Packard BioScience) and washed three times with cold 50 mM Tris-HCl (pH 7.4 buffer). Nonspecific binding was measured in the presence of 10 μM MPEP. After adding 45 μl of microscint 40 (Canberra Packard S.A., Zurich, Switzerland) and shaking for 20 min, the radioactivity on the filter was counted on a Packard Top-count microplate scintillation counter with quenching correction (3 min).

The corresponding results for compounds having _EC50 values less than or equal to 20 nM are shown in the table of examples below.

Comparison of the compounds of the present invention with the most similar compounds described in Examples 106 and 109 of WO2011128279:

As can be seen in the table below, the compounds of the present invention exhibit a distinctly different profile compared to structurally similar compounds of the prior art, which is an advantage when compounds exhibiting NAM activity are desired.

The compound of formula I can be prepared by the method given below, by the method given in the examples or by similar procedures. The appropriate reaction conditions of the individual reaction steps are known to those skilled in the art. The reaction sequence is not limited to the order shown in the scheme, but, depending on the raw material and their respective reactivity, the order of reactions steps can be freely changed. Raw material is commercially available, or can be prepared by a method similar to the method given below, by the method described in the literature cited in the description or in the examples or by methods known in the art.

The compounds of formula I of the present invention and their pharmaceutically acceptable salts can be prepared by methods known in the art, for example, by the process variations described below, which include

The compound of formula II

wherein X is a halogen atom selected from bromine or iodine

Reaction with the appropriate aryl-acetylene of formula III

To form a compound of formula I

wherein the substituent R ¹ is described above, in enantiomerically pure form having the absolute stereochemistry shown in Formula I, or by using the racemic form of II followed by chiral separation of I to obtain an optically pure enantiomer; and

If necessary, the obtained compound is converted into a pharmaceutically acceptable acid addition salt.

The preparation of compounds of formula I is also described in more detail in Schemes 1 to 3 and Examples 1-4.

Solution 1

The synthesis of the compound of formula IIa is described in scheme 1. The halo-pyridine compound of formula IIa can be obtained by the palladium catalyzed reaction of the appropriately substituted cyclic urea of suitable dihalogenated pyridines such as 2-bromo-5-iodo-pyridine and formula 5 (Scheme 1). The reaction of the bicyclic urea of 2-chloro- or 2-fluoro-pyridine with bromine or iodine at the 5-position and formula 5 can also be formed by the aromatic nucleophilic substitution reaction using alkaline conditions such as NaH/THF or cesium carbonate/DMF to form the compound of formula IIa. The compound of formula 5 can be obtained by the 2-amino-1-carboxylic acid of the appropriately protected formula 1, which can be obtained using a procedure similar to that described in Gorrea & al., Tetrahedron asymmetry, 21, 339 (2010). The acid function of 1 is converted to the corresponding isocyanate 2 via an acyl azide intermediate (Curtius rearrangement), which is then cyclized to form the bicyclic urea compound 3. The free NH group of 3 can be alkylated according to standard procedures to form compound 4, which is then deprotected to give the cyclic urea 5. Optically pure intermediates 2 to 5 can also be obtained starting from optically pure protected acids of formula 1 or by separating racemic mixtures at any stage of the synthesis using procedures known to those skilled in the art.

Option 2

Wherein R ¹ in this scheme means a phenyl group substituted by (R ¹ ) _n .

Compounds of formula IIa (X = Br, I) can be reacted with an appropriate aryl-acetylene of formula III (wherein W is hydrogen or an in situ cleavable protecting group such as trialkylsilyl- or aryldialkylsilyl, preferably hydrogen or trimethylsilyl) under palladium-catalyzed coupling conditions (Sonogashira reaction) to form compounds of formula Ia, wherein the substituent R ¹ is described above. Another possibility involves reacting IIa with trimethylsilylacetylene to produce a compound of formula Ia, wherein R ¹ is trimethylsilyl, followed by a second Sonogashira reaction with an appropriate aryl bromide or aryl iodide to produce a compound of formula I (scheme not shown).

In case the amino acid derivative 1 is in racemic form, the enantiomers can be separated at any given stage during the synthesis of the compound of formula I using procedures known to those skilled in the art.

The order of the reactions to produce compounds of formula I can also be reversed (Scheme 3). In this case, the Sonogashira reaction between the aryl acetylene derivative III and the dihalo-pyridine is first performed to produce the aryl acetylene-pyridine compound of formula 6, which is then condensed with the bicyclic urea 1 to produce the compound of formula I.

Option 3

Wherein R ¹ in this scheme means a phenyl group substituted by (R ¹ ) _n .

The pharmaceutical salt of the compound of formula I can be easily prepared according to methods known per se and considering the nature of the compound to be converted into salt. Inorganic or organic acid such as, for example, hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid, phosphoric acid or citric acid, formic acid, fumaric acid, maleic acid, acetic acid, succinic acid, tartaric acid, methanesulfonic acid, p-toluenesulfonic acid etc. are suitable for forming the pharmaceutical salt of the compound of basic formula I. The compound comprising alkali metal or alkaline earth metal (for example, sodium, potassium, calcium, magnesium etc.), basic amine or basic amino acid is suitable for forming the pharmaceutical salt of acidic compound.

As mentioned above, the compound of Formula I and pharmaceutically acceptable salts thereof are metabotropic glutamate receptor antagonists, and can be used to treat or prevent the disease of mGluR5 receptor mediation, such as acute and/or chronic neurological disorders, cognitive impairment and amnesia, and acute and chronic pain. Treatable neurological disorders are such as epilepsy, schizophrenia, anxiety disorders, acute, traumatic and chronic degenerative processes of the nervous system, such as Alzheimer's disease, senile dementia, Huntington's disease, ALS, multiple sclerosis, the dementia caused by AIDS, eye damage, retinopathy, idiopathic Parkinson's disease or the Parkinson's disease caused by drugs and the condition causing glutamate deficiency function, such as such as muscle spasms, convulsions, migraine, urinary incontinence, nicotine addiction, psychosis, opioid addiction, anxiety disorders, vomiting, movement disorders and depression. Other treatable indications are the limited brain function caused by bypass surgery or transplantation, poor cerebral blood supply, spinal cord injury, head injury, the hypoxia caused by pregnancy, cardiac arrest and hypoglycemia.

The compounds of formula I and their pharmaceutically acceptable salts are particularly useful as analgesics. Types of pain that can be treated include inflammatory pain such as arthritis and rheumatoid arthritis, vasculitis, neuropathic pain such as trigeminal neuralgia or herpes neuralgia, diabetic neuropathy pain, causalgia, hyperalgesia, severe chronic pain, postoperative pain, and pain associated with various conditions such as cancer, angina, renal or biliary colic, menstruation, migraine, and gout.

The pharmacological activities of the compounds were tested using the following methods:

The cDNA encoding rat mGlu 5a receptor was transiently transfected into EBNA cells using the procedure described by E.-J.Schlaeger and K.Christensen (Cytotechnology 1998, 15, 1-13). [Ca ²⁺ ] i was measured on mGlu 5a transfected EBNA cells after incubation at 37°C with Fluo 3-AM (obtained by FLUKA, 0.5 μM final concentration) for 1 hour and then washing 4 times with assay buffer (DMEM supplemented with Hank's salts and 20 mM HEPES). [Ca ²⁺ ] i was measured using a fluorometric imaging plate reader (FLIPR, Molecular Devices Corporation, La Jolla, CA, USA). When compounds were evaluated as antagonists, they were tested against 10 μM glutamate as an antagonist.

Inhibition (antagonist) curves were fitted with a four-parameter logistic equation using iterative nonlinear curve fitting software Origin (Microcal Software Inc., Northampton, MA, USA) to give _IC50 and Hill coefficient.

The Ki value of the tested compound is given. The Ki value is defined by the following formula:

Wherein the _IC50 value is the concentration of the test compound in μM that antagonizes the compound's effect by 50%. [L] is the concentration and the _EC50 value is the concentration of the test compound in μM that produces 50% stimulation.

The compounds of the present invention are mGluR 5a receptor antagonists.The activity of the compounds of formula I measured in the above assay is in the range of _K1 < 100 μΜ.

The compounds of formula I and their pharmaceutically acceptable salts can be used as medicaments, for example, in the form of pharmaceutical preparations. The pharmaceutical preparations can be administered orally, for example, in the form of tablets, coated tablets, lozenges, hard and soft gelatin capsules, solutions, emulsions or suspensions. However, the administration can also be carried out rectally, for example, in the form of suppositories, or parenterally, for example, in the form of injections.

The compounds of formula I and their pharmaceutically acceptable salts can be processed together with pharmaceutically inert, inorganic or organic carriers for the preparation of pharmaceutical preparations. For example, lactose, corn starch or its derivatives, talc, stearic acid or its salts can be used as such carriers for tablets, coated tablets, lozenges and hard gelatin capsules. Suitable carriers for soft gelatin capsules are, for example, vegetable oils, waxes, fats, semi-solid and liquid polyols; however, depending on the properties of the active substance, a carrier is generally not required in the case of soft gelatin capsules. Suitable carriers for preparing solutions and syrups are, for example, water, polyols, sucrose, invert sugar, glucose, etc. Auxiliary agents such as alcohols, polyols, glycerol, vegetable oils, etc. can be used in aqueous solutions for injection of water-soluble salts of the compounds of formula I, but generally speaking, this is not essential. Suitable carriers for suppositories are, for example, natural or hardened oils, waxes, fats, semi-liquid or liquid polyols, etc.

In addition, the pharmaceutical preparations may contain preservatives, solubilizers, stabilizers, wetting agents, emulsifiers, sweeteners, colorants, flavorings, salts for varying the osmotic pressure, buffers, masking agents or antioxidants. They may also contain other therapeutically valuable substances.

As already mentioned, medicaments containing a compound of formula I or a pharmaceutically acceptable salt thereof and a therapeutically inert excipient are also an object of the present invention, as are processes for the preparation of these medicaments, which comprise bringing one or more compounds of formula I or a pharmaceutically acceptable salt thereof and, if desired, one or more other therapeutically valuable substances into galenic form together with one or more therapeutically inert carriers.

Dosage can vary within a wide range and will, of course, be adapted to individual needs in each specific case. Typically, effective doses for oral or parenteral administration are between 0.01 and 10 mg/kg/day, with 0.1 to 5 mg/kg/day being preferred for all described indications. The daily dose for an adult weighing 70 kg is correspondingly between 0.7 and 700 mg/day, preferably between 7 and 350 mg/day.

The following examples are provided to further illustrate the present invention:

Example 1

(-)-(1S,5R)-2-Methyl-4-(5-(phenylethynyl)pyridin-2-yl)-2,4-diazabicyclo[3.2.0]heptan-3-one

Step 1: (rac)-(1SR,2RS)-2-(naphthalen-2-ylmethoxycarbonylamino)cyclobutanecarboxylic acid methyl ester :

To a well-stirred solution of (rac)-(cis)-(1RS,2SR)-cyclobutane-1,2-dicarboxylic acid monomethyl ester (CAS: 31420-52-7) (10.8 g, 68.3 mmol) and N-methylmorpholine (7.6 g, 8.26 ml, 75.1 mmol) in 160 ml of 1,2-dichloroethane was added diphenylphosphoryl azide (20.7 g, 16.2 ml, 75.1 mmol) dropwise. After stirring at room temperature for 10 min, the reaction was warmed to 60°C. 2-naphthylmethanol (10.8 g, 68.3 mmol) and copper (I) chloride (68 mg, 0.68 mmol) were added and the reaction was stirred at 60°C for another 16 h. The reaction was concentrated in vacuo, and the light brown oily residue (51 g) was diluted with 15 ml of dichloromethane and purified by flash chromatography on silica gel (SiO ₂ (650 g), ethyl acetate/heptane 20:80) to give 16.8 g of impure material containing unreacted naphthylmethanol. The material was repurified (Aminophase, 0% to 35%, ethyl acetate in heptane gradient) to give 11.1 g (52%) of the title compound as a white crystalline solid, MS: m/e=314.2 (M+H ⁺ ).

Step 2: (rac)-(1SR,2RS)-2-(naphthalen-2-ylmethoxycarbonylamino)cyclobutanecarboxylic acid

To a well-stirred solution of (rac)-(1SR,2RS)-2-(naphthalen-2-ylmethoxycarbonylamino)cyclobutanecarboxylic acid methyl ester (Example 1, Step 1) (4.2 g, 13.4 mmol) in 20 ml of dioxane was added water (70 ml). The solution was cooled to 5°C and 53.6 ml (26.8 mmol) of 0.5 M sodium hydroxide solution was added dropwise over 5 minutes. After stirring at 5°C for 1 hour, the reaction was warmed to room temperature with vigorous stirring. The clear solution was then cooled to 5°C and the pH was adjusted to 2.5 by adding approximately 13 ml of 2N hydrochloric acid solution. The reaction was worked up with ethyl acetate. After drying, filtering, and concentrating in vacuo, 3.87 g (97%) of the title compound were obtained as a crystalline white solid, MS: m/e = 300.2 (M+H ⁺ ).

Step 3: (rac)-(1RS,5SR)-3-oxo-2,4-diaza-bicyclo[3.2.0]heptane-2-carboxylic acid naphthalene- 2-methyl methyl ester

A solution of (rac)-(1SR,2RS)-2-(naphthalen-2-ylmethoxycarbonylamino)cyclobutanecarboxylic acid (Example 1, Step 2) (2.34 g, 7.82 mmol) and N-methylmorpholine (0.79 g, 0.86 ml, 7.82 mmol) in 34 ml of dichloroethane was stirred at room temperature for 10 min. Diphenylphosphoric acid azide (2.15 g, 1.69 ml, 7.82 mmol) was then added dropwise at room temperature, and the colorless solution was stirred at room temperature for 1 h, during which time the solution turned pale yellow. The solution was then warmed to 50°C, stirred for 6 h, and cooled. After purging with dichloromethane/water, the combined organic phases were evaporated to dryness to give a yellow solid, which was recrystallized from ethyl acetate/heptane. The title compound (1.86 g, 80%) was obtained as a white crystalline solid, MS: m/e = 297.3 (M+H ⁺ ).

Step 4: (rac)-(1RS,5SR)-4-methyl-3-oxo-2,4-diaza-bicyclo[3.2.0]heptane-2- Naphthyl-2-ylmethyl formate

To a solution of (racemic)-(1RS,5SR)-3-oxo-2,4-diaza-bicyclo[3.2.0]heptane-2-carboxylic acid naphthalen-2-ylmethyl ester (Example 1, Step 3) (1.13 g, 3.81 mmol) in 11 ml of DMF was added a 60% suspension of sodium hydride in mineral oil (0.198 g, 4.96 mmol). The suspension was stirred at room temperature for 35 minutes (gas evolution), then iodomethane (0.81 g, 0.36 ml, 5.72 mmol) was added and the mixture was stirred at room temperature overnight. After quenching by adding 3 ml of saturated ammonium chloride solution and concentrating in vacuo, the residue was purified by separation with ethyl acetate/water. The combined organic phases were dried and concentrated in vacuo. The residue was purified by flash chromatography on silica gel (50 g), eluting with a gradient of 20-100% ethyl acetate in heptane to afford 0.98 g (82%) of a colorless oil, MS: m/e = 311.2 (M+H ⁺ ).

Step 5: (rac)-(1SR,5RS)-2-methyl-2,4-diaza-bicyclo[3.2.0]heptan-3-one

A solution of (rac)-(1RS,5SR)-4-methyl-3-oxo-2,4-diaza-bicyclo[3.2.0]heptane-2-carboxylic acid naphthalen-2-ylmethyl ester (Example 1, Step 4) (0.97 g, 3.13 mmol) in 15 ml of methanol was hydrogenated over 10% Pd/C (0.333 g, 0.313 mmol) for 48 h. The solution was purged with argon, the catalyst was filtered off and washed with ethyl acetate. The filtrate was concentrated in vacuo. The residue was purified by flash chromatography on silica gel (20 g) eluting with a gradient of 50–100% ethyl acetate in heptane to give 0.375 g (95%) of the title compound as a crystalline white solid which was used directly in the next step without further characterization.

Step 6: (rac)-(1RS,5SR)-2-(5-iodo-pyridin-2-yl)-4-methyl-2,4-diaza-bicyclo [3.2.0] Heptan-3-one

To a solution of (rac)-(1SR,5RS)-2-methyl-2,4-diaza-bicyclo[3.2.0]heptan-3-one (Example 1, Step 5) (375 mg, 2.97 mmol) and 2-fluoro-5-iodopyridine (683 mg, 3.06 mmol) in DMF (10 ml) was added a 60% suspension of sodium hydride in mineral oil (155 mg, 3.86 mmol). The reaction was stirred at room temperature overnight. After quenching by adding 3 ml of saturated ammonium chloride solution and concentrating in vacuo to remove DMF, the residue was purified by ethyl acetate/water separation. After drying and concentrating in vacuo, the residue was purified by flash chromatography (SiO ₂ , 20 g) using a gradient of 0% to 65% ethyl acetate in heptane. The title compound (549 mg, 56%) was obtained as a crystalline white solid, MS: m/e=330.1 (M+H ⁺ ).

Step 7: (rac)-(+/-)-(1SR,5RS)-2-methyl-4-(5-(phenylethynyl)pyridin-2-yl)-2, 4-diazabicyclo[3.2.0]heptan-3-one

In a 5 ml microwave tube, 110 mg (0.33 mmol) of (rac)-(1RS,5SR)-2-(5-iodo-pyridin-2-yl)-4-methyl-2,4-diaza-bicyclo[3.2.0]heptan-3-one (Example 1, Step 6) was dissolved in 1.5 ml of DMF. Argon was bubbled through the solution. Ethynylbenzene (73 μl, 68 mg, 0.67 mmol), bis(triphenylphosphine)palladium(II) chloride (14 mg, 20 μmol), copper(I) iodide (1.9 mg, 10.0 μmol), triphenylphosphine (1.8 mg, 7.7 μmol) and 107 μl of triethylamine (101 mg, 140 μl, 1.0 mmol) were added. The dark brown solution was stirred at 60°C for 3 h. The reaction was worked up with ethyl acetate/water, dried and concentrated in vacuo. The residue was purified by flash chromatography (silica gel, 20 g, 0% to 50% EtOAc in heptane gradient) to afford 95 mg (94%) of the title compound as a light brown crystalline solid, MS: m/e = 304.2 (M+H ⁺ ).

Step 8: (-)-(1S,5R)-2-methyl-4-(5-(phenylethynyl)pyridin-2-yl)-2,4-diazabicyclo [3.2.0] heptan-3-one and (+)-(1R,5S)-2-methyl-4-(5-(phenylethynyl)pyridin-2-yl)-2,4-diazabicyclo [3.2.0] Heptan-3-one

A racemic mixture of (rac)-(+/-)-(1SR,5RS)-2-methyl-4-(5-(phenylethynyl)pyridin-2-yl)-2,4-diazabicyclo[3.2.0]heptan-3-one (Example 1, Step 7) (95 mg) was separated by chiral HPLC (Chiralpak-5 cm x 50 cm, 20 mM; 40% isopropanol/heptane, 35 ml/min, 18 bar). Peak detection was achieved using a UV detector and an optical rotation detector (ORD), with one peak having a negative signal ((-)-enantiomer) and the other having a positive signal ((+)-enantiomer). The (-)-enantiomer, (-)-(1S,5R)-2-methyl-4-(5-(phenylethynyl)pyridin-2-yl)-2,4-diazabicyclo[3.2.0]heptan-3-one (39 mg), was obtained as a crystalline light yellow solid, MS: m/e = 304.1 (M+H ⁺ ). The (+)-enantiomer, (+)-(1R,5S)-2-methyl-4-(5-(phenylethynyl)pyridin-2-yl)-2,4-diazabicyclo[3.2.0]heptan-3-one (40 mg), was obtained as a light yellow solid, MS: m/e = 304.1 (M+H ⁺ ).

Example 2

(-)-(1R,5S)-2-[5-(3-Fluoro-phenylethynyl)-pyridin-2-yl]-4-methyl-2,4-diazabicyclo[3.2.0]heptan-3-one

The title compound was prepared according to the general procedure of Example 1, Step 7 by the following steps: Starting from (rac)-(1RS,5SR)-2-(5-iodo-pyridin-2-yl)-4-methyl-2,4-diaza-bicyclo[3.2.0]heptan-3-one (Example 1, Step 6) (110 mg) and 1-ethynyl-3-fluorobenzene, 107 mg (96%) of racemic material ((+/-)-(1R,5S)-2-[5-(3-fluoro-phenylethynyl)-pyridin-2-yl]-4-methyl-2,4-diazabicyclo[3.2.0]heptan-3-one was obtained as a light yellow crystalline solid; MS: m/e=322.3 (M+H ⁺ ), which was then separated by chiral HPLC using similar separation conditions as described in Example 1, Step 8, to give the enantiomerically pure enantiomer (-)-(1R,5S)-2-[5-(3-fluoro-phenylethynyl)-pyridin-2-yl]-4-methyl-2,4-diazabicyclo[3.2.0]heptan-3-one as a light yellow solid, MS: m/e=322.3 (M+H ⁺ ); and its enantiomer (+)-(1S,5R)-2-[5-(3-fluoro-phenylethynyl)-pyridin-2-yl]-4-methyl-2,4-diazabicyclo[3.2.0]heptan-3-one as a light yellow solid; MS: m/e=322.3 (M+H ⁺ ).

Example 3

(-)-(1R,5S)-2-[5-(4-Fluoro-phenylethynyl)-pyridin-2-yl]-4-methyl-2,4-diazabicyclo[3.2.0]heptan-3-one

The title compound was prepared according to the general procedure of Example 1, Step 7 by the following steps: Starting from (rac)-(1RS,5SR)-2-(5-iodo-pyridin-2-yl)-4-methyl-2,4-diaza-bicyclo[3.2.0]heptan-3-one (Example 1, Step 6) (110 mg) and 1-ethynyl-4-fluorobenzene, 104 mg (97%) of racemic material ((+/-)-(rac)-(1SR,5RS)-2-[5-(4-fluoro-phenylethynyl)-pyridin-2-yl]-4-methyl-2,4-diazabicyclo[3.2.0]heptan-3-one was obtained as a light yellow crystalline solid; MS: m/e=322.3 (M+H ⁺ ), which was then separated by chiral HPLC using similar separation conditions as described in Example 1, Step 8, to give the enantiomerically pure enantiomer (-)-(1R,5S)-2-[5-(4-fluoro-phenylethynyl)-pyridin-2-yl]-4-methyl-2,4-diazabicyclo[3.2.0]heptan-3-one as a light yellow solid, MS: m/e=322.3 (M+H ⁺ ); and its enantiomer (+)-(1S,5R)-2-[5-(4-fluoro-phenylethynyl)-pyridin-2-yl]-4-methyl-2,4-diazabicyclo[3.2.0]heptan-3-one as a light yellow solid; MS: m/e=322.3 (M+H ⁺ ).

Example 4

(-)-(1R,5S)-2-[5-(2,5-Difluoro-phenylethynyl)-pyridin-2-yl]-4-methyl-2,4-diazabicyclo[3.2.0]heptan-3-one

The title compound was prepared according to the general procedure of Example 1, Step 7 by the following steps: Starting from (rac)-(1RS,5SR)-2-(5-iodo-pyridin-2-yl)-4-methyl-2,4-diaza-bicyclo[3.2.0]heptan-3-one (Example 1, Step 6) (110 mg) and 2-ethynyl-1,4-difluorobenzene, 110 mg (97%) of racemic material ((+/-)-(rac)-(1SR,5RS)-2-[5-(2,5-difluoro-phenylethynyl)-pyridin-2-yl]-4-methyl-2,4-diazabicyclo[3.2.0]heptan-3-one was obtained as a light yellow crystalline solid; MS: m/e=340.1 (M+H ⁺ ), which was then separated by chiral HPLC using similar separation conditions as described in Example 1, Step 8, to give the enantiomerically pure enantiomer (-)-(1R,5S)-2-[5-(2,5-difluoro-phenyl-ethynyl)-pyridin-2-yl]-4-methyl-2,4-diazabicyclo[3.2.0]heptan-3-one as a light yellow solid, MS: m/e=340.1 (M+H ⁺ ); and its enantiomer (+)-(1S,5R)-2-[5-(2,5-difluoro-phenyl-ethynyl)-pyridin-2-yl]-4-methyl-2,4-diazabicyclo[3.2.0]heptan-3-one as a light yellow solid; MS: m/e=340.1 (M+H ⁺ ).

Preparation of pharmaceutical composition:

Example 1

Tablets having the following composition are prepared in a conventional manner:

Example II

Tablets having the following composition are prepared in a conventional manner:

Example III

Capsules with the following composition were prepared:

The active ingredient, crystalline lactose and microcrystalline cellulose having a suitable particle size are uniformly mixed with each other, sieved, and then talc and magnesium stearate are mixed in. The final mixture is filled into hard gelatin capsules of suitable size.

Claims (6)

1. A compound of formula I, in ^R1 is hydrogen or F; n is 1 or 2 Or its medicinal acid addition salt. 2. The compound of formula I according to claim 1, wherein the compound is (1S,5R)-2-methyl-4-(5-(phenylethynyl)pyridin-2-yl)-2,4-diazabicyclo[3.2.0]hepta-3-one; (1R,5S)-2-(5-((4-fluorophenyl)ethynyl)pyridin-2-yl)-4-methyl-2,4-diazabicyclo[3.2.0]hepta-3-one; (1R,5S)-2-(5-((3-fluorophenyl)ethynyl)pyridin-2-yl)-4-methyl-2,4-diazabicyclo[3.2.0]hepta-3-one; or (1R,5S)-2-(5-((2,5-difluorophenyl)ethynyl)pyridin-2-yl)-4-methyl-2,4-diazabicyclo[3.2.0]hepta-3-one. 3. A method for preparing a compound of formula I according to any one of claims 1 or 2, the method comprising the following steps: Compounds of Formula II Where X is a halogen atom selected from bromine or iodine. Reaction with aryl-acetylene of Formula III To form compounds of formula I Wherein substituent ^R1 is as described above, it is the enantiomeric pure form having the absolute stereochemistry shown in Formula I, or the optically pure enantiomer is obtained by using the racemic form of II followed by chiral separation of I, wherein W is hydrogen or a trialkylsilyl or aryldialkylsilyl that can be cracked in situ; and If necessary, the obtained compound can be converted into a pharmaceutical acid addition salt. 4. A pharmaceutical composition comprising a compound according to any one of claims 1 or 2 and a therapeutically active carrier. 5. Use of the compound claimed in any one of claims 1 or 2 for the preparation of a medicament for the treatment of anxiety and pain, depression, Parkinson's disease, and gastroesophageal reflux disease. 6. Compounds, selected from: (+)-(1R,5S)-2-methyl-4-(5-(phenylethynyl)pyridin-2-yl)-2,4-diazabicyclo[3.2.0]hepta-3-one; (+)-(1S,5R)-2-(5-((3-fluorophenyl)ethynyl)pyridin-2-yl)-4-methyl-2,4-diazabicyclo[3.2.0]hepta-3-one; (+)-(1S,5R)-2-(5-((4-fluorophenyl)ethynyl)pyridin-2-yl)-4-methyl-2,4-diazabicyclo[3.2.0]hepta-3-one; or (+)-(1S,5R)-2-(5-((2,5-difluorophenyl)ethynyl)pyridin-2-yl)-4-methyl-2,4-diazabicyclo[3.2.0]hepta-3-one.