HK1208030B - Novel pyrazine derivatives as cb2 receptor agonists - Google Patents

Description

Pyrazine derivatives as CB2 receptor agonists

The present invention relates to organic compounds useful for treatment and/or prevention in mammals and in particular to compounds that are preferential agonists of cannabinoid receptor 2.

The present invention particularly relates to compounds of formula (I) or pharmaceutically acceptable salts or esters thereof,

in

^R1 is cycloalkylalkoxy or haloalkoxy;

^R2 is a cycloalkyl group or a halogenated azetidinyl group;

^R3 and ^R4 are independently selected from alkyl, alkoxy, alkoxyalkyl and alkoxycarbonylalkyl;

or ^R and ^R together with the nitrogen atom to which they are attached form a heterocyclyl or substituted heterocyclyl, wherein heterocyclyl is pyrrolidinyl, morpholinyl, oxomorpholinyl, 2-oxo-5-aza-bicyclo[2.2.1]heptyl, 7-oxa-4-aza-spiro[2.5]octyl, piperazinyl, 2-oxa-6-aza-spiro[3.4]octyl, piperidinyl, thiomorpholinyl or 5-azaspiro[2.4]heptyl, and wherein substituted heterocyclyl is a heterocyclyl substituted with one to four substituents independently selected from the group consisting of alkyl, halogen, aminocarbonyl, hydroxyalkyl, alkoxycarbonyl, alkylthiocarbamoyl, alkylcarbonyloxy and hydroxy.

The compounds of formula (I) are particularly useful for treating or preventing, for example, pain, atherosclerosis, age-related macular degeneration, diabetic retinopathy, glaucoma, retinal vein occlusion, retinopathy of prematurity, ocular ischemic syndrome, geographic atrophy, diabetes mellitus, inflammation, inflammatory bowel disease, ischemia-reperfusion injury, acute liver failure, liver fibrosis, lung fibrosis, kidney fibrosis, systemic fibrosis, acute allograft rejection, and the like. rejection, chronic allograft nephropathy, diabetic nephropathy, glomerulonephropathy, cardiomyopathy, heart failure, myocardial ischemia, myocardial infarction, systemic sclerosis, thermal injury, burns, hypertrophic scars, keloids, gingivitis pyrexia, liver cirrhosis or tumors, regulation of bone mass, neurodegeneration, amyotrophic lateral sclerosis, stroke, transient ischemic attack, or uveitis.

The compounds of formula (I) are particularly useful for treating or preventing diabetic retinopathy, retinal vein occlusion or uveitis.

Cannabinoid receptors are a type of cell membrane receptor that belongs to the G protein-coupled receptor superfamily. There are currently two known subtypes, cannabinoid receptor 1 (CB1) and cannabinoid receptor 2 (CB2). CB1 receptors are primarily expressed in the central nervous system (i.e., the amygdala, cerebellum, and hippocampus) and are expressed to a lesser extent in the periphery. CB2, encoded by the CNR2 gene, is primarily expressed on cells of the immune system, such as macrophages and T-cells (Ashton, J.C. et al. Curr Neuropharmacol 2007, 5(2), 73-80; Miller, A.M. et al. Br J Pharmacol 2008, 153(2), 299-308; Centonze, D., et al. Curr Pharm Des 2008, 14(23), 2370-42), and in the gastrointestinal system (Wright, K.L. et al. Br J Pharmacol 2008, 153(2), 263-70). CB2 receptors are also widely distributed in the brain, where they are primarily found on microglia rather than neurons (Cabral, G.A. et al. Br J Pharmacol 2008, 153(2): 240-51).

Interest in CB2 receptor agonists has steadily increased over the past decade (currently 30-40 patent applications/year) due to the fact that several of the early compounds have shown beneficial effects in preclinical models of a number of human diseases, including chronic pain (Beltramo, M. Mini Rev Med Chem 2009, 9(1), 11-25), atherosclerosis (Mach, F. et al., J Neuroendocrinol 2008, 20 Suppl 1, 53-7), bone regulation (Bab, I. et al., Br J Pharmacol 2008, 153(2), 182-8), neuroinflammation (Cabral, G.A. et al., J Leukoc Biol 2005, 78(6), 1192-7), ischemia/reperfusion injury (Pacher, P. et al., Br J Pharmacol 2008, 153(2), 252-62), systemic fibrosis (Akhmetshina, A. et al., Arthritis Rheum 2009, 60(4), 1129-36; Garcia-Gonzalez, E. et al., Rheumatology (Oxford) 2009, 48(9), 1050-6), hepatic fibrosis (Julien, B. et al., Gastroenterology 2005, 128(3), 742-55; Munoz-Luque, J. et al., J Pharmacol Exp Ther 2008, 324(2), 475-83).

Ischemia/reperfusion (I/R) injury is the main cause of tissue damage in conditions such as stroke, myocardial infarction, cardiopulmonary bypass and other vascular surgeries, and organ transplantation, and is the primary mechanism of end-organ damage that complicates the circulatory shock process of various etiologies. All of these conditions are characterized by the interruption of normal blood supply, resulting in insufficient tissue oxygenation. Reoxygenation, such as reperfusion, is the ultimate treatment for restoring normal tissue oxygenation. However, the lack of oxygen and nutrition from the blood produces conditions in which the restoration of circulation leads to further tissue damage. The damage caused by reperfusion injury is partly due to the inflammatory response of the damaged tissue. The white blood cells transported to the area by the newly returned blood release a large amount of inflammatory factors such as interleukins and free radicals in response to tissue damage. The restored blood flow reintroduces intracellular oxygen, which damages cellular proteins, DNA, and plasma membranes.

Remote ischemic preconditioning (RIPC) represents a strategy that exploits the body's endogenous protective abilities to counteract the damage caused by ischemia and reperfusion. It describes the intriguing phenomenon that temporary non-lethal ischemia and reperfusion of one organ or tissue confers resistance to subsequent events of "lethal" ischemia-reperfusion injury in a distant organ or tissue. Although several hypotheses have been proposed, the actual mechanism by which temporary ischemia and reperfusion of an organ or tissue confers protection is currently unknown.

The humoral hypothesis proposes that endogenous substances produced in remote organs or tissues (such as adenosine, bradykinin, opioids, CGRP, endocannabinoids, angiotensin I, or some other as yet unidentified humoral factors) enter the bloodstream and activate their respective receptors in target tissues and thereby restore the various intracellular pathways involved in cardioprotection during ischemic preconditioning.

Recent data suggest that endocannabinoids and their receptors, particularly CB2, may be involved in preconditioning and contribute to the prevention of reperfusion injury by downregulating the inflammatory response (Pacher, P. et al., Br J Pharmacol 2008, 153(2), 252-62). Specifically, recent studies using CB2 tool agonists have shown the efficacy of this concept for reducing I/R injury in the heart (Defer, N. et al., Faseb J 2009, 23(7), 2120-30), brain (Zhang, M. et al., J Cereb Blood Flow Metab 2007, 27(7), 1387-96), liver (Batkai, S. et al., Faseb J 2007, 21(8), 1788-800) and kidney (Feizi, A. et al., Exp Toxicol Pathol 2008, 60(4-5), 405-10).

In addition, over the past few years, a growing body of literature has shown that CB2 may also be of interest in subchronic and chronic conditions. Specific upregulation of CB1 and CB2 has been shown in animal models of chronic diseases associated with fibrosis (Garcia-Gonzalez, E. et al., Rheumatology (Oxford) 2009, 48(9), 1050-6; Yang, Y.Y. et al., Liver Int 2009, 29(5), 678-85) and is associated with CB2-related expression in myofibroblasts, the cells responsible for the fibrotic process.

Activation of CB2 receptors by selective CB2 agonists has indeed been shown to produce an antifibrotic effect in diffuse systemic sclerosis (Garcia-Gonzalez, E. et al., Rheumatology (Oxford) 2009, 48(9), 1050-6) and CB2 receptors have been implicated in experimental dermal fibrosis (Akhmetshina, A. et al., Arthritis Rheum 2009, 60(4), 1129-36) and in liver pathophysiology, including fibrogenesis associated with chronic liver disease (Lotersztajn, S. et al., Gastroenterol Clin Biol 2007, 31(3), 255-8; Mallat, A. et al., Expert Opin Ther Targets 2007, 11(3), 403-9; Lotersztajn, S. et al., Br J Pharmacol 2008, 153(2), 286-9).

The compounds of the present invention bind to and modulate CB2 receptors and have lower CB1 receptor activity.

In the present specification, the term "alkyl", alone or in combination, means a straight-chain or branched alkyl group having 1 to 8 carbon atoms, in particular a straight-chain or branched alkyl group having 1 to 6 carbon atoms, and more particularly a straight-chain or branched alkyl group having 1 to 4 carbon atoms. Examples of straight-chain and branched _C1 - _C8 alkyl groups are methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, the isomeric pentyls, the isomeric hexyls, the isomeric heptyls and the isomeric octyls, in particular methyl, ethyl, propyl, butyl and pentyl, more particularly methyl, ethyl, propyl, isopropyl, isobutyl, tert-butyl and isopentyl. Particular examples of alkyl groups are methyl, ethyl, isopropyl, butyl and tert-butyl, especially methyl, ethyl and tert-butyl.

The term "cycloalkyl", alone or in combination, means a cycloalkyl ring having 3 to 8 carbon atoms, and in particular a cycloalkyl ring having 3 to 6 carbon atoms. Examples of cycloalkyl groups are cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl, cycloheptyl and cyclooctyl. A particular example of a cycloalkyl group is cyclopropyl.

The term "alkoxy", alone or in combination, means a radical of the formula alkyl-O-, wherein the term "alkyl" has the meaning given above, such as methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, sec-butoxy and tert-butoxy. Particular "alkoxy" radicals are methoxy and ethoxy, and in particular methoxy.

The term "oxy", alone or in combination, signifies a -O- group.

The term "halogen" or "halo", alone or in combination, denotes fluorine, chlorine, bromine or iodine, and is particularly fluorine, chlorine or bromine, more particularly fluorine and chlorine. The term "halo", in combination with another group, denotes substitution of the group by at least one halogen, particularly by one to five halogens, in particular one to four halogens, i.e. one, two, three or four halogens. Particular "halogen" is fluorine.

The term "haloalkyl", alone or in combination, means an alkyl group substituted by at least one halogen, particularly by one to five halogens, especially one to three halogens. Particular "haloalkyl" is trifluoroethyl.

The term "haloalkoxy", alone or in combination, means an alkoxy group substituted by at least one halogen, particularly by one to five halogens, especially one to three halogens. Particular "haloalkoxy" groups are trifluoroethoxy, fluoroethoxy, fluoropropoxy, difluoroethoxy and difluoropropoxy. Particular "haloalkoxy" group is trifluoroethoxy.

The terms "hydroxyl" and "hydroxy", alone or in combination, refer to a -OH group.

The term "carbonyl", alone or in combination, signifies a -C(O)- group.

The term "amino", alone or in combination, means a primary amino group (-NH ₂ ), a secondary amino group (-NH-), or a tertiary amino group (-N-).

The term "aminocarbonyl", alone or in combination, signifies the -C(O) _-NH2 group.

The term "pharmaceutical salt" refers to those salts that keep the biological effectiveness and character of free alkali or free acid, and they are not biologically or otherwise unsuitable. Said salt is formed with inorganic acids such as hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid, phosphoric acid, particularly hydrochloric acid, and organic acids such as acetic acid, propionic acid, glycolic acid, pyruvic acid, oxalic acid, maleic acid, malonic acid, succinic acid, fumaric acid, tartaric acid, citric acid, benzoic acid, cinnamic acid, mandelic acid, methanesulfonic acid, ethanesulfonic acid, p-toluenesulfonic acid, salicylic acid, N-acetylcysteine. In addition, these salts can be prepared by adding of inorganic bases or organic bases to free acid. The salt deriving from inorganic bases includes, but is not limited to, sodium, potassium, lithium, ammonium, calcium, magnesium salts. The salt that derives from organic base includes, but is not limited to the salt of following material: primary, secondary and tertiary amine, substituted amine, comprise naturally occurring substituted amine, cyclic amine and basic ion exchange resin, as isopropylamine, trimethylamine, diethylamine, triethylamine, tripropylamine, ethanolamine, lysine, arginine, N- ethylpiperidine, piperidine, polyamine resin.The compound of formula (I) also can exist with the form of zwitterion.The pharmaceutically acceptable salt of the compound of particularly preferred formula (I) is the salt of hydrochloric acid, hydrobromic acid, sulfuric acid, phosphoric acid and methanesulfonic acid.

"Pharmaceutically acceptable esters" means that the compounds of formula (I) can be derivatized at functional groups to provide derivatives that are capable of conversion back to the parent compound in vivo. Examples of such compounds include physiologically acceptable and metabolically labile ester derivatives, such as methoxymethyl ester, methylthiomethyl ester, and pivaloyloxymethyl ester. In addition, any physiologically acceptable equivalents of the compounds of formula (I) that are similar to the metabolically labile esters and are capable of producing the parent compound of formula (I) in vivo are within the scope of this invention.

If one of the starting materials or the compound of formula (I) contains one or more functional groups that are unstable or reactive under the reaction conditions of one or more reaction steps, then suitable protecting groups can be introduced before the key steps using methods well known in the art (as described in, for example, T.W.Greene and P.G.M.Wuts in "Protective Groups in Organic Chemistry," 3rd edition, 1999, Wiley, New York). Such protecting groups can be removed at a later stage of the synthesis using standard methods described in the literature. Examples of protecting groups are tert-butyloxycarbonyl (Boc), 9-fluorenylmethyl carbamate (Fmoc), 2-trimethylsilylethyl carbamate (Teoc), benzyloxycarbonyl (Cbz) and p-methoxybenzyloxycarbonyl (Moz).

The compounds of formula (I) may contain several asymmetric centers and may exist as optically pure enantiomers, mixtures of enantiomers, such as, for example, racemates, mixtures of diastereomers, diastereomeric racemates or mixtures of diastereomeric racemates.

The term "asymmetric carbon atom" refers to a carbon atom having four different substituents. According to the Cahn-Ingold-Prelog Convention, an asymmetric carbon atom can be in the "R" or "S" configuration.

The present invention particularly relates to compounds of formula (I), wherein

^R3 and ^R4 are independently selected from alkyl, alkoxy, alkoxyalkyl and alkoxycarbonylalkyl;

or ^R and ^R together with the nitrogen atom to which they are attached form a heterocyclyl or substituted heterocyclyl, wherein heterocyclyl is pyrrolidinyl, morpholinyl, oxomorpholinyl, 2-oxo-5-aza-bicyclo[2.2.1]heptyl, 7-oxa-4-aza-spiro[2.5]octyl, piperazinyl, 2-oxa-6-aza-spiro[3.4]octyl, piperidinyl or thiomorpholinyl, and wherein substituted heterocyclyl is a heterocyclyl substituted with one to four substituents independently selected from the group consisting of alkyl, halogen, aminocarbonyl, hydroxyalkyl, alkoxycarbonyl, alkylthiocarbamoyl and alkylcarbonyloxy.

The present invention particularly relates to:

A compound of formula (I), wherein R ¹ is cycloalkylalkoxy;

A compound of formula (I), wherein R ¹ is cyclopropylmethoxy or trifluoroethoxy;

A compound of formula (I), wherein R ¹ is cyclopropylmethoxy;

A compound of formula (I), wherein R ² is cyclopropyl or difluoroazetidinyl;

A compound of formula (I) wherein ^R and ^R are independently selected from alkyl, alkoxy, alkoxyalkyl and alkoxycarbonylalkyl, or wherein ^R and ^R together with the nitrogen atom to which they are attached form a substituted pyrrolidinyl, substituted morpholinyl, substituted oxomorpholinyl, substituted piperidinyl, substituted thiomorpholinyl or substituted 5-azaspiro[2.4]heptyl, wherein the substituted pyrrolidinyl, substituted morpholinyl, substituted oxomorpholinyl, substituted piperidinyl, substituted thiomorpholinyl or substituted 5-azaspiro[2.4]heptyl is a pyrrolidinyl, morpholinyl, oxomorpholinyl, piperidinyl, thiomorpholinyl or 5-azaspiro[2.4]heptyl substituted with one to four substituents independently selected from alkyl, halogen, aminocarbonyl, hydroxyalkyl, alkoxycarbonyl, alkylthiocarbamoyl, alkylcarbonyloxy and hydroxy, or wherein R and R are taken together with the nitrogen atom to which they are attached to form a substituted pyrrolidinyl, substituted morpholinyl, substituted oxomorpholinyl, substituted piperidinyl, substituted thiomorpholinyl or ⁵ -azaspiro[2.4]heptyl ⁴ together with the nitrogen atom to which they are attached form 2-oxo-5-aza-bicyclo[2.2.1]heptyl, 7-oxa-4-aza-spiro[2.5]octyl, piperazinyl or 2-oxa-6-aza-spiro[3.4]octyl;

A compound of formula (I) wherein R ³ and R ⁴ are independently selected from alkyl, alkoxy, alkoxyalkyl and alkoxycarbonylalkyl, or wherein R ³ and R ⁴ together with the nitrogen atom to which they are attached form a substituted pyrrolidinyl, substituted morpholinyl, substituted oxomorpholinyl, substituted piperidinyl or substituted thiomorpholinyl, wherein the substituted pyrrolidinyl, substituted morpholinyl, substituted oxomorpholinyl, substituted piperidinyl or substituted thiomorpholinyl is a pyrrolidinyl, morpholinyl, oxomorpholinyl, piperidinyl or thiomorpholinyl substituted with one to four substituents independently selected from alkyl, halogen, aminocarbonyl, hydroxyalkyl, alkoxycarbonyl, alkylthiocarbamoyl and alkylcarbonyloxy, or wherein R ³ and R ⁴ together with the nitrogen atom to which they are attached form 2-oxo-5-aza-bicyclo[2.2.1] Heptyl, 7-oxa-4-aza-spiro[2.5]octyl, piperazinyl or 2-oxa-6-aza-spiro[3.4]octyl;

A compound of formula (I), wherein ^R3 and ^R4 are independently selected from alkyl, alkoxy and alkoxyalkyl, or wherein ^R3 and ^R4 together with the nitrogen atom to which they are attached form a heterocyclyl or substituted heterocyclyl, wherein the heterocyclyl is pyrrolidinyl, morpholinyl or 5-azaspiro[2.4]heptyl, and wherein the substituted heterocyclyl is a heterocyclyl substituted with one to three substituents independently selected from alkyl, halogen and aminocarbonyl;

A compound of formula (I) wherein R ³ and R ⁴ are independently selected from methyl, tert-butyl, methoxyethyl or methoxybutyl, or wherein R ³ and R ⁴ together with the nitrogen atom to which they are attached form dimethylmorpholinyl, dimethylpyrrolidinyl, (aminocarbonyl)(difluoro)pyrrolidinyl, (aminocarbonyl)(dimethyl)pyrrolidinyl or (aminocarbonyl)5-azaspiro[2.4]heptyl;

A compound of formula (I), wherein R ³ and R ⁴ are independently selected from alkyl, alkoxy and alkoxyalkyl, or wherein R ³ and R ⁴ together with the nitrogen atom to which they are attached form a heterocyclyl or substituted heterocyclyl, wherein the heterocyclyl is pyrrolidinyl or morpholinyl, and wherein the substituted heterocyclyl is a heterocyclyl substituted with one to three substituents independently selected from alkyl, halogen and aminocarbonyl;

A compound of formula (I) wherein R ³ and R ⁴ are independently selected from methyl, tert-butyl, methoxyethyl or methoxybutyl, or wherein R ³ and R ⁴ together with the nitrogen atom to which they are attached form dimethylmorpholinyl, dimethylpyrrolidinyl, (aminocarbonyl)(difluoro)pyrrolidinyl or (aminocarbonyl)(dimethyl)pyrrolidinyl;

A compound of formula (I), wherein R ³ and R ⁴ are independently selected from methyl, ethyl, isopropyl, tert-butyl, methoxyethyl, ethoxycarbonylmethyl and methoxybutyl, or wherein R ³ and R ⁴ together with the nitrogen atom to which they are attached form methylpyrrolidinyl, dimethylpyrrolidinyldimethylmorpholinyl, 2-oxo-5-aza-bicyclo[2.2.1]heptyl, difluoropyrrolidinyl, 7-oxa-4-aza-spiro[2.5]octyl, methoxycarbonylpyrrolidinyl, (aminocarbonyl)(difluoro)pyrrolidinyl, hydroxyethylpiperazinyl, oxomorpholinyl, dimethylthiocarbamoylpyrrolidinyl, (methylcarbonyloxy)(methyl)pyrrolidinyl, tetrafluoropyrrolidinyl, methylcarbonyloxypyrrolidinyl, 2-oxa-6-aza-spiro[3.4]octyl, aminocarbonylpiperidinyl, aminocarbonylthiomorpholinyl, (aminocarbonyl)5-azaspiro[2.4]heptyl or (hydroxy)(alkyl)(aminocarbonyl)pyrrolidinyl; and

A compound of formula (I) wherein ^R and ^R are independently selected from methyl, ethyl, isopropyl, tert-butyl, methoxyethyl, ethoxycarbonylmethyl and methoxybutyl, or wherein ^R and ^R together with the nitrogen atom to which they are attached form methylpyrrolidinyl, dimethylpyrrolidinyldimethylmorpholinyl, 2-oxo-5-aza-bicyclo[2.2.1]heptyl, difluoropyrrolidinyl, 7-oxa-4-aza-spiro[2.5]octyl, methoxycarbonylpyrrolidinyl, (aminocarbonyl)(difluoro)pyrrolidinyl, hydroxyethylpiperazinyl, oxomorpholinyl, dimethylthiocarbamoylpyrrolidinyl, (methylcarbonyloxy)(methyl)pyrrolidinyl, tetrafluoropyrrolidinyl, methylcarbonyloxypyrrolidinyl, 2-oxa-6-aza-spiro[3.4]octyl, aminocarbonylpiperidinyl or aminocarbonylthiomorpholinyl.

The present invention also relates to compounds of formula (I) selected from the group consisting of:

(5-Cyclopropyl-6-cyclopropylmethoxy-pyrazin-2-yl)-((R)-2-methyl-pyrrolidin-1-yl)-methanone;

[6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazin-2-yl]-((R)-2-methyl-pyrrolidin-1-yl)-methanone;

6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carboxylic acid tert-butyl-(2-methoxy-ethyl)-amide;

[6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazin-2-yl]-(3,3-dimethyl-morpholin-4-yl)-methanone;

[6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazin-2-yl]-((S)-2-methyl-pyrrolidin-1-yl)-methanone;

[6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazin-2-yl]-(1R,4R)-2-oxa-5-aza-bicyclo[2.2.1]hept-5-yl-methanone;

6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carboxylic acid tert-butyl-methyl-amide;

[6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazin-2-yl]-(3,3-difluoro-pyrrolidin-1-yl)-methanone;

6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carboxylic acid ethyl-isopropyl-amide;

[6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazin-2-yl]-(7-oxa-4-aza-spiro[2.5]octan-4-yl)-methanone;

{tert-Butyl-[6-cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carbonyl]-amino}-acetic acid ethyl ester;

6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carboxylic acid (2-methoxy-1,1-dimethyl-ethyl)-methyl-amide;

[6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazin-2-yl]-(2,2-dimethyl-morpholin-4-yl)-methanone;

5-Cyclopropyl-6-cyclopropylmethoxy-pyrazine-2-carboxylic acid (2-methoxy-1,1-dimethyl-ethyl)-methyl-amide;

(5-Cyclopropyl-6-cyclopropylmethoxy-pyrazin-2-yl)-(2,2-dimethyl-pyrrolidin-1-yl)-methanone;

(S)-1-(5-Cyclopropyl-6-cyclopropylmethoxy-pyrazine-2-carbonyl)-pyrrolidine-2-carboxylic acid methyl ester;

(5-Cyclopropyl-6-cyclopropylmethoxy-pyrazin-2-yl)-(7-oxa-4-aza-spiro[2.5]octan-4-yl)-methanone;

(S)-1-(5-Cyclopropyl-6-cyclopropylmethoxy-pyrazine-2-carbonyl)-4,4-difluoro-pyrrolidine-2-carboxylic acid amide;

(S)-1-[6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carbonyl]-4,4-difluoro-pyrrolidine-2-carboxylic acid amide;

[6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazin-2-yl]-[4-(2-hydroxy-ethyl)-piperazin-1-yl]-methanone;

[6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazin-2-yl]-(2,2-dimethyl-pyrrolidin-1-yl)-methanone;

(R)-1-[6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carbonyl]-pyrrolidine-2-carboxylic acid methyl ester;

4-[6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carbonyl]-morpholin-2-one;

(R)-1-[6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carbonyl]-pyrrolidine-2-carboxylic acid dimethylamide;

Acetic acid 1-(5-cyclopropyl-6-cyclopropylmethoxy-pyrazine-2-carbonyl)-3-methyl-pyrrolidin-3-yl ester;

(5-Cyclopropyl-6-cyclopropylmethoxy-pyrazin-2-yl)-(3,3,4,4-tetrafluoro-pyrrolidin-1-yl)-methanone;

Acetic acid (S)-1-[6-cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carbonyl]-pyrrolidin-3-yl ester;

[6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazin-2-yl]-(2-oxa-6-aza-spiro[3.4]octan-6-yl)-methanone;

Acetic acid 1-[6-cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carbonyl]-3-methyl-pyrrolidin-3-yl ester;

[6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazin-2-yl]-(3,3,4,4-tetrafluoro-pyrrolidin-1-yl)-methanone;

5-(3,3-Difluoro-azetidin-1-yl)-6-(2,2,2-trifluoro-ethoxy)-pyrazine-2-carboxylic acid tert-butyl-methyl-amide;

[5-(3,3-Difluoro-azetidin-1-yl)-6-(2,2,2-trifluoro-ethoxy)-pyrazin-2-yl]-(2,2-dimethyl-pyrrolidin-1-yl)-methanone;

1-[6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carbonyl]-piperidine-2-carboxylic acid amide;

1-(5-Cyclopropyl-6-cyclopropylmethoxy-pyrazine-2-carbonyl)-4,4-dimethyl-pyrrolidine-2-carboxylic acid amide;

1-[6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carbonyl]-4,4-dimethyl-pyrrolidine-2-carboxylic acid amide;

(-)-1-[6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carbonyl]-piperidine-2-carboxylic acid amide;

(-)-4-[6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carbonyl]-thiomorpholine-3-carboxylic acid amide;

(-)-1-[6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carbonyl]-4,4-dimethyl-pyrrolidine-2-carboxylic acid amide; and

(-)-1-(5-Cyclopropyl-6-cyclopropylmethoxy-pyrazine-2-carbonyl)-4,4-dimethyl-pyrrolidine-2-carboxylic acid amide.

The present invention also relates to compounds of formula (I) selected from the group consisting of:

(±)-5-[6-(cyclopropylmethoxy)-5-(3,3-difluoroazetidin-1-yl)pyrazine-2-carbonyl]-5-azaspiro[2.4]heptane-6-carboxamide;

(2S)-1-[6-(cyclopropylmethoxy)-5-(3,3-difluoroazetidin-1-yl)pyrazine-2-carbonyl]-4-hydroxy-4-methylpyrrolidine-2-carboxamide; and

(2S)-1-[5-(3,3-Difluoroazetidin-1-yl)-6-(2,2-difluoroethoxy)pyrazine-2-carbonyl]-4,4-difluoro-pyrrolidine-2-carboxamide.

The present invention also relates to compounds of formula (I) selected from the group consisting of:

6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carboxylic acid tert-butyl-(2-methoxy-ethyl)-amide;

[6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazin-2-yl]-(3,3-dimethyl-morpholin-4-yl)-methanone;

6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carboxylic acid tert-butyl-methyl-amide;

6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carboxylic acid (2-methoxy-1,1-dimethyl-ethyl)-methyl-amide;

(5-Cyclopropyl-6-cyclopropylmethoxy-pyrazin-2-yl)-(2,2-dimethyl-pyrrolidin-1-yl)-methanone;

(S)-1-[6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carbonyl]-4,4-difluoro-pyrrolidine-2-carboxylic acid amide;

[6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazin-2-yl]-(2,2-dimethyl-pyrrolidin-1-yl)-methanone;

1-(5-Cyclopropyl-6-cyclopropylmethoxy-pyrazine-2-carbonyl)-4,4-dimethyl-pyrrolidine-2-carboxylic acid amide; and

(-)-1-[6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carbonyl]-4,4-dimethyl-pyrrolidine-2-carboxylic acid amide.

The present invention also relates to the compound (±)-5-[6-(cyclopropylmethoxy)-5-(3,3-difluoroazetidin-1-yl)pyrazine-2-carbonyl]-5-azaspiro[2.4]heptane-6-carboxamide.

The compound of formula (I) can be prepared by a process comprising coupling a compound of formula II with an amine of formula III

wherein ^R1 and ^R2 are as defined above,

wherein R ³ and R ⁴ are as defined above, the coupling is carried out by amide coupling methods known in the art, such as, for example, with the aid of an amide coupling agent under basic conditions, and, if desired, the resulting compound of formula (I) is converted into a pharmaceutically acceptable salt thereof.

Unless otherwise indicated, in the following schemes, R ¹ to R ⁴ have the meanings given above.

The compound of formula III or II may contain functional groups that will interfere with the coupling procedure described in the amide coupling step (II to I). In this case, it will be understood that III or II will need to be appropriately protected by methods known in the art before the amide coupling step is carried out, and that the compound will need to be deprotected by methods known in the art after the coupling step to obtain the compound of formula (I).

Amide coupling agents for the reaction of the compound of formula II with the amine of formula III are, for example, N,N'-carbonyldiimidazole (CDI), N,N'-dicyclohexylcarbodiimide (DCC), 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDCI), 1-[bis(dimethylamino)-methylene]-1H-1,2,3-triazolo[4,5-b]pyridine-3-oxide hexafluorophosphate (HATU), 1-hydroxy-1,2,3-benzotriazole (HOBT), O-benzotriazol-1-yl-N,N,N',N'-tetramethyluronium tetrafluoroborate (TBTU), or O-benzotriazole-N,N,N',N'-tetramethyl-uronium-hexafluoro-phosphate (HBTU). Particular coupling agents are TBTU and HATU. Suitable bases include triethylamine, N-methylmorpholine and in particular diisopropylethylamine.An alternative method known in the art may start with the preparation of the acid chloride from II and coupling with an amine of formula III in the presence of a suitable base.

The synthesis of compounds of formula (I) can, for example, be achieved according to the following scheme.

Following the process according to Scheme 1, compound AA (5-chloro-pyrazine-2-carboxylic acid methyl ester, CAN 33332-25-1) can be used as a starting material for the synthesis of compound Ia, wherein R2 is a haloazetidinyl group ( ^R2a is a haloazetidinyl group). AA is commercially available or can be synthesized by one skilled in the art as described in the literature.

Compound AB can be prepared from AA by reacting with the corresponding halide azetidine in the presence of a base, especially triethylamine, in an inert solvent, especially dioxane, at a temperature between room temperature and 45°C.

The conversion of compound AB to AC can be achieved by electrophilic aromatic bromination in a suitable solvent, especially with N-bromosuccinimide in chloroform at elevated temperature, especially at 60°C, or by using other conditions known in the literature.

Saponification of esters of general formula AC by methods known to those skilled in the art using, for example, aqueous solutions of LiOH, NaOH or KOH in tetrahydrofuran/ethanol or other suitable solvents at temperatures between 0° C. and the reflux temperature of the solvent used gives acids of general formula AD.

Solution 1

Compound AD can be converted to compound II-a by reacting with an appropriately substituted primary or secondary alcohol AE in the presence of a base such as potassium hydroxide with or without an inert solvent such as DMSO at room temperature to the reflux temperature of the solvent, especially at room temperature.

Compound II-a can be further elaborated to compound I-a by coupling a compound of formula II-a with an amine of formula III by amide coupling methods known in the art, such as, for example, with the aid of an amide coupling reagent under basic conditions. For example, coupling agents such as N,N'-carbonyl-diimidazole (CDI), N,N'-dicyclohexylcarbodiimide (DCC), 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDCI), 1-[bis(dimethylamino)-methylene]-1H-1,2,3-triazolo[4,5-b]pyridine-3-oxide hexafluorophosphate (HATU), 1-hydroxy-1,2,3-benzotriazole (HOBT), O-benzotriazol-1-yl-N,N,N',N'-tetramethyluronium tetrafluoroborate (TBTU), and O-benzotriazole-N,N,N',N'-tetramethyl-uronium-hexafluoro-phosphate (HBTU) can be used to achieve this transformation. A convenient method is to use, for example, O-benzotriazole-N, N, N', N'-tetramethyl-urea-hexafluoro-phosphate (HBTU) and a base such as N-ethyl-N-isopropylpropane-2-amine (DIEA) in an inert solvent such as dimethylformamide at room temperature. An alternative method known in the art can begin by preparing the acyl chloride by II-a and coupling with an amine of formula III in the presence of a suitable base.

Amines III are commercially available, described in the literature, can be synthesized by a person skilled in the art or obtained as described in the experimental part.

If one of the starting materials, a compound of formula AE or III, contains one or more functional groups that are unstable or reactive under the reaction conditions of one or more reaction steps, a suitable protecting group (P) can be introduced prior to the key step using methods well known in the art (as described, for example, in T. W. Greene et al., "Protective Groups in Organic Chemistry", John Wiley and Sons Inc. New York 1999, 3rd edition). Such protecting groups can be removed at a later stage of the synthesis using standard methods known in the art.

If one or more compounds of formula AE or III contain a chiral center, the pyridine of formula I-a can be obtained as a mixture of diastereomers or enantiomers, which can be separated by methods known in the art, such as (chiral) HPLC or crystallization. Racemic compounds can be separated into their enantiomers via diastereomeric salts, for example, by crystallization or by special chromatographic methods using chiral adsorbents or chiral eluents to separate the enantiomers.

Following the procedure according to Scheme 2, compound BA (3,5-dibromo-2-pyrazinamine, CAN 24241-18-7) can be used as a starting material for the synthesis of compound Ib, wherein R ² is cycloalkyl (R ^2b is cycloalkyl).

Compound BA can be converted to compound BB by reacting with an appropriately substituted primary or secondary alcohol AE in the presence of a base such as sodium hydride with or without an inert solvent such as DMF at a temperature ranging from room temperature to the reflux temperature of the solvent, especially at room temperature.

Boc-protection of compounds of general formula BB by methods known to those skilled in the art using, for example, di-tert-butyl dicarbonate in an inert solvent, especially dichloromethane, in the presence of a catalytic amount of a base, especially dimethylaminopyridine, yields compounds of general formula BC (if an excess of di-tert-butyl dicarbonate is used in the reaction).

Option 2

Compounds of general formula BD can be obtained from compounds of general formula BC by palladium(II), especially palladium(II) acetate, catalyzed carbonylation in the presence of a suitable base such as a tertiary amine base, especially triethylamine, in a suitable solvent such as an alcohol, especially methanol.

Solvolysis of boc-protected compounds of general formula BD by methods known to those skilled in the art using, for example, protic solvents, especially methanol, at elevated temperature, especially reflux temperature, yields compounds of general formula BE.

Compounds of general formula BF can be obtained from compounds of general formula BE by reaction with a nitrosating agent such as a metal nitrite or an organic nitrite, more particularly tert-butyl nitrite, in the presence of a bromine source such as hydrobromic acid or more particularly trimethylsilyl bromide, in a suitable solvent such as a halogenated hydrocarbon, more particularly dibromomethane.

Compounds BH wherein ^R is cycloalkyl ( ^R is cycloalkyl) can be prepared from BF by reacting a suitably substituted cycloalkyl or cycloalkenyl metal species BG, in particular cyclopropylboronic acid or cyclopropyltrifluoro-borate salts, with BF in the presence of a suitable catalyst, in particular a palladium catalyst such as palladium(II) acetate, in the presence of cyclohexylphosphine, in an inert solvent such as toluene, at room temperature to the reflux temperature of the solvent, in the presence of a suitable base such as potassium phosphate. In the event that one skilled in the art chooses to couple with a cycloalkenyl metal species such as a cycloalkenyl borate, compound BH will be obtained only after an additional hydrogenation step, for example by hydrogenation with hydrogen in the presence of a palladium catalyst such as palladium on carbon, in an inert solvent such as ethanol, at a suitable temperature and pressure, in particular at ambient temperature and pressure.

Saponification of esters of general formula BH by methods known to those skilled in the art using, for example, aqueous LiOH, NaOH or KOH in tetrahydrofuran/ethanol or other suitable solvents at temperatures between 0° C. and the reflux temperature of the solvent used yields acids of general formula II-b.

Compound II-b can be further elaborated to compound I-b by coupling a compound of formula II-b with an amine of formula III by amide coupling methods known in the art, such as, for example, with the aid of an amide coupling reagent under basic conditions. For example, coupling agents such as N,N'-carbonyl-diimidazole (CDI), N,N'-dicyclohexylcarbodiimide (DCC), 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDCI), 1-[bis(dimethylamino)-methylene]-1H-1,2,3-triazolo[4,5-b]pyridine-3-oxide hexafluorophosphate (HATU), 1-hydroxy-1,2,3-benzotriazole (HOBT), O-benzotriazol-1-yl-N,N,N',N'-tetramethyluronium tetrafluoroborate (TBTU), and O-benzotriazole-N,N,N',N'-tetramethyl-uronium-hexafluoro-phosphate (HBTU) can be used to achieve this transformation. A convenient method is to use, for example, O-benzotriazole-N, N, N', N'-tetramethyl-urea-hexafluoro-phosphate (HBTU) and a base such as N-ethyl-N-isopropylpropane-2-amine (DIEA) in an inert solvent such as dimethylformamide at room temperature. An alternative method known in the art can begin by preparing the acyl chloride from II-b and coupling it with an amine of formula III in the presence of a suitable base.

Amines III are commercially available or described in the literature and can be synthesized by a person skilled in the art or obtained as described in the experimental part.

If one of the starting materials, a compound of formula AE, BG or III, contains one or more functional groups that are unstable or reactive under the reaction conditions of one or more reaction steps, a suitable protecting group (P) can be introduced prior to the key step using methods well known in the art (as described, for example, in T. W. Greene et al., "Protective Groups in Organic Chemistry", John Wiley and Sons Inc. New York 1999, 3rd edition). Such protecting groups can be removed at a later stage of the synthesis using standard methods known in the art.

If one or more compounds of formula AE, BG or III contain a chiral center, the pyridine of formula I-b may be obtained as a mixture of diastereomers or enantiomers, which can be separated by methods known in the art, such as (chiral) HPLC or crystallization. Racemic compounds can be separated into their enantiomers via diastereomeric salts, for example, by crystallization or by special chromatographic methods using chiral adsorbents or chiral eluents to separate the enantiomers.

The present invention also relates to a method for preparing a compound of formula (I), which comprises reacting a compound of formula (II) in the presence of NHR ³ R ⁴ , an amide coupling agent and a base.

wherein R ¹ to R ⁴ are as defined above.

Amide coupling agents and bases suitable for use in the process of the present invention are as defined above.

The present invention also relates in particular to:

The compounds of formula (I) are useful in treating or preventing pain, atherosclerosis, age-related macular degeneration, diabetic retinopathy, glaucoma, retinal vein occlusion, retinopathy of prematurity, ocular ischemic syndrome, geographic atrophy, diabetes mellitus, inflammation, inflammatory bowel disease, ischemia-reperfusion injury, acute liver failure, liver fibrosis, lung fibrosis, kidney fibrosis, systemic fibrosis, acute allograft rejection, and rejection, chronic allograft nephropathy, diabetic nephropathy, glomerulonephropathy, cardiomyopathy, heart failure, myocardial ischemia, myocardial infarction, systemic sclerosis, thermal injury, burns, hypertrophic scars, keloids, gingivitis pyrexia, liver cirrhosis or tumor, regulation of bone mass, neurodegeneration, amyotrophic lateral sclerosis, stroke, transient ischemic attack, or uveitis;

Use of a compound of formula (I) in the preparation of a medicament for treating or preventing pain, atherosclerosis, age-related macular degeneration, diabetic retinopathy, glaucoma, retinal vein occlusion, retinopathy of prematurity, ocular ischemic syndrome, geographic atrophy, diabetes, inflammation, inflammatory bowel disease, ischemia-reperfusion injury, acute liver failure, liver fibrosis, pulmonary fibrosis, renal fibrosis, systemic fibrosis, acute allograft rejection, chronic allograft nephropathy, diabetic nephropathy, glomerulonephropathy, cardiomyopathy, heart failure, myocardial ischemia, myocardial infarction, systemic sclerosis, thermal injury, burns, hypertrophic scars, keloids, gingivitis fever, cirrhosis or tumors, bone modulation, neurodegeneration, amyotrophic lateral sclerosis, stroke, transient ischemic attack or uveitis;

A compound of formula (I) for use in the treatment or prevention of pain, atherosclerosis, age-related macular degeneration, diabetic retinopathy, glaucoma, retinal vein occlusion, retinopathy of prematurity, ocular ischemic syndrome, geographic atrophy, diabetes, inflammation, inflammatory bowel disease, ischemia-reperfusion injury, acute liver failure, liver fibrosis, pulmonary fibrosis, renal fibrosis, systemic fibrosis, acute allograft rejection, chronic allograft nephropathy, diabetic nephropathy, glomerulonephropathy, cardiomyopathy, heart failure, myocardial ischemia, myocardial infarction, systemic sclerosis, thermal injury, burns, hypertrophic scars, keloids, gingivitis fever, cirrhosis or tumors, bone modulation, neurodegeneration, amyotrophic lateral sclerosis, stroke, transient ischemic attack or uveitis; and

A method for treating or preventing pain, atherosclerosis, age-related macular degeneration, diabetic retinopathy, glaucoma, retinal vein occlusion, retinopathy of prematurity, ocular ischemic syndrome, geographic atrophy, diabetes, inflammation, inflammatory bowel disease, ischemia-reperfusion injury, acute liver failure, liver fibrosis, pulmonary fibrosis, renal fibrosis, systemic fibrosis, acute allograft rejection, chronic allograft nephropathy, diabetic nephropathy, glomerulonephropathy, cardiomyopathy, heart failure, myocardial ischemia, myocardial infarction, systemic sclerosis, thermal injury, burns, hypertrophic scars, keloids, gingivitis, liver cirrhosis or tumors, bone modulation, neurodegeneration, amyotrophic lateral sclerosis, stroke, transient ischemic attack or uveitis, the method comprising administering to a patient in need thereof an effective amount of a compound of formula (I).

The present invention particularly relates to compounds of formula (I) for use in treating or preventing ischemia, reperfusion injury, liver fibrosis or kidney fibrosis, in particular ischemia or reperfusion injury.

The present invention also particularly relates to compounds of formula (I) for use in the treatment or prevention of diabetic retinopathy, retinal vein occlusion or uveitis.

The present invention also relates to compounds of formula (I) prepared according to the process of the present invention.

Another embodiment of the present invention provides a pharmaceutical composition or medicine comprising a compound of the present invention and a therapeutically inert carrier, diluent or excipient, and methods for preparing such compositions and medicines using the compounds of the present invention. In one example, the compound of formula (I) can be formulated as follows: by mixing a physiologically acceptable carrier, i.e., a carrier that is non-toxic to the recipient at the dose and concentration employed, at an appropriate pH at ambient temperature and to a desired degree of purity into a galenic dosage form. The pH of the formulation depends primarily on the specific application and the concentration of the compound, but is preferably anywhere within the range of about 3 to about 8. In one example, the compound of formula (I) is formulated in acetate buffer at pH 5. In another embodiment, the compound of formula (I) is sterile. The compound can be stored, for example, as a solid or amorphous composition, as a lyophilized formulation, or as an aqueous solution.

The composition is formulated, dosed, and administered in a manner consistent with good medical practice. Factors for consideration include the specific condition being treated, the specific mammal being treated, the clinical condition of the individual patient, the cause of the condition, the site of delivery of the agent, the method of administration, the timing of administration, and other factors known to practitioners.

The compounds of the present invention can be administered by any suitable means, including oral, topical (including buccal and sublingual), rectal, vaginal, transdermal, parenteral, subcutaneous, intraperitoneal, intrapulmonary, intradermal, intrathecal and epidural and intranasal, and, if desired for local treatment, intralesional administration. Parenteral infusions include intramuscular, intravenous, intraarterial, intraperitoneal, or subcutaneous administration. The compounds of the present invention can be used particularly by intravitreal administration.

The compounds of the present invention can be administered in any convenient administration form, for example, tablets, powders, capsules, solutions, dispersions, suspensions, syrups, sprays, suppositories, gels, emulsions, patches, etc. Such compositions may contain conventional components of pharmaceutical preparations, for example, diluents, carriers, pH adjusters, sweeteners, fillers, and other active agents.

Typical formulations are prepared by mixing a compound of the invention with a carrier or excipient. Suitable carriers and excipients are well known to those skilled in the art and are described in detail in, for example, Ansel, Howard C., et al., Ansel's Pharmaceutical Dosage Forms and Drug Delivery Systems. Philadelphia: Lippincott, Williams & Wilkins, 2004; Gennaro, Alfonso R., et al., Remington: The Science and Practice of Pharmacy. Philadelphia: Lippincott, Williams & Wilkins, 2000; and Rowe, Raymond C. Handbook of Pharmaceutical Excipients. Chicago, Pharmaceutical Press, 2005. The formulation may also include one or more buffers, stabilizers, surfactants, wetting agents, lubricants, emulsifiers, suspending agents, preservatives, antioxidants, opaquing agents, glidants, processing aids, colorants, sweeteners, flavoring agents, flavor enhancers, diluents and other known additives to provide a good presentation of the drug (i.e., the compound of the present invention or its pharmaceutical composition) or to assist in the preparation of a pharmaceutical product (i.e., a drug).

The invention will now be illustrated by the following non-limiting examples.

Example

abbreviation

bp = boiling point; CAN = CAS registry number; DBU = 1,8-diazabicyclo[5.4.0]undec-7-ene; DCM = dichloromethane; DIEA = N-ethyl-N-isopropylpropan-2-amine; DMF = dimethylformamide; DMSO = dimethyl sulfoxide; dppf = 1,1′-bis(diphenylphosphino)ferrocene; EI = electron ionization; ESI = electrospray; h = hour; HATU = 2-(3H-[1,2,3]triazolo[4,5-b]pyridine-3-yl)-1,2-diol; = 1-Hydroxy-1-Methyl-2-nitropropane-2-yl)-1,1,3,3-tetramethylisothiazolyl hexafluorophosphate (V); HBTU = O-benzotriazole-N,N,N',N'-tetramethyl-uronium-hexafluoro-phosphate; HPLC = LC = high performance liquid chromatography; m-CPBA = meta-chloroperbenzoic acid; mp = melting point; MS = mass spectrum; NMR data are reported in parts per million (δ) relative to the internal standard tetramethylsilane and referenced to the deuterium lock signal from the sample solvent ( _d6- DMSO, unless otherwise stated); coupling constants (J) are in Hertz; Rt = retention time; TBME = methyl tert-butyl ether, TBTU = O-(benzotriazol-1-yl)-N,N,N',N'-tetramethyl-uronium-tetrafluoroborate; TEMPO = 2,2,6,6-tetramethylpiperidin-1-oxyl; TFA = trifluoroacetic acid; THF = tetrahydrofuran; tlc = thin layer chromatography.

Example 1

(5-Cyclopropyl-6-cyclopropylmethoxy-pyrazin-2-yl)-((R)-2-methyl-pyrrolidin-1-yl)-methanone

a) 5-Bromo-3-cyclopropylmethoxy-pyrazin-2-ylamine

To a solution of cyclopropyl-methanol (16.47 mL, 205.62 mmol) in DMSO (200 mL) was added sodium hydride (60% in oil, 4.93 g, 205.62 mmol) at 0°C and the reaction mixture was stirred at 0°C for 2 hours. To this suspension was added 3,5-dibromo-pyrazin-2-ylamine (20 g, 79.09 mmol) in DMSO (40 mL) and the mixture was stirred at ambient temperature for 12 hours. The mixture was partitioned between water (300 mL) and ethyl acetate and the organic phase was dried _{over Na2SO4} , filtered and concentrated in vacuo. The crude material was purified by chromatography (silica gel, 500 g, 10% ethyl acetate in hexanes) to yield the desired product (14 g, 72.52%) as a yellow solid; LC-MS (UV peak area, ESI) 94.7%, 244.0 [MH ⁺ ].

b) Di-tert-butyl [5-bromo-3-(cyclopropylmethoxy)pyrazin-2-yl]iminodicarbonate

To a solution of 5-bromo-3-cyclopropylmethoxy-pyrazine-2-ylamine (30 g, 122.91 mmol) in DCM (200 mL) was added di-tert-butyl dicarbonate (67.7 mL, 307.26 mmol) and 4-dimethylaminopyridine (1.49 g, 12.29 mmol). The reaction mixture was stirred at ambient temperature for 18 hours. The mixture was partitioned between water (300 mL) and dichloromethane and the organic phase was separated, washed with brine, dried over Na ₂ SO ₄ , filtered and concentrated in vacuo. The crude material was purified by chromatography (silica gel, 600 g, 5%-7% ethyl acetate in hexanes) to produce the desired product (45 g, 82.8%) as a yellow oil; LC-MS (UV peak area, ESI) 94.7%, 445.0 [MH ⁺ ].

c) Methyl 5-[di(tert-butoxycarbonyl)amino]-6-(cyclopropylmethoxy)pyrazine-2-carboxylate

To a solution of di-tert-butyl [5-bromo-3-(cyclopropylmethoxy)pyrazin-2-yl]imino-dicarbonate (20 g, 45.05 mmol) in methanol (200 mL) was added _PdCl₂ ·dppf· _CH₂Cl₂ (4.04 g, 4.95 mmol) and _{triethylamine} (9.5 mL, 67.57 mmol) and the mixture was stirred at 80°C under a 32 bar carbon monoxide atmosphere for 5 hours. After expansion and cooling, the solid was removed by filtration. The organic phase was separated, washed with brine (300 mL), _dried over _Na₂SO₄ , filtered, and concentrated in vacuo. The crude material was purified by chromatography (Combi-Flash, 120 g, 15%-20% ethyl acetate in hexanes) to yield the desired product (14 g, 73.7%) as a yellow semisolid; LC-MS (UV peak area, ESI) 96.1%, 424.4 [ ^MH⁺ ].

d) 5-Amino-6-cyclopropylmethoxy-pyrazine-2-carboxylic acid methyl ester

Methyl 5-[bis(tert-butoxycarbonyl)amino]-6-(cyclopropylmethoxy)pyrazine-2-carboxylate (15 g, 35.46 mmol) was suspended in methanol (150 mL) and water (225 mL) and the mixture was heated at 100° C. for 12 hours. After cooling, a white solid was formed, which was filtered and dried in vacuo to give the title compound (5.7 g, 72.2%) as a cream solid; LC-MS (UV peak area, ESI) 99.7%, 224.2 [MH+].

e) 5-Bromo-6-cyclopropylmethoxy-pyrazine-2-carboxylic acid methyl ester

5-Amino-6-cyclopropylmethoxy-pyrazine-2-carboxylic acid methyl ester (10 g, 44.84 mmol) was suspended in dibromomethane (150 mL). To this suspension was added trimethylsilyl bromide (14.8 mL, 112.11 mmol) at 0°C, followed by tert-butyl nitrite (57.5 mL, 448.43 mmol) and the mixture was stirred at this temperature for 3 hours. The mixture was partitioned between water (190 mL) and ethyl acetate, and the organic phase was washed with brine (200 mL ₎ , dried over _Na₂SO₄ , filtered, and concentrated in vacuo. The crude material was purified by chromatography (Combi-Flash, 80 g, 20% ethyl acetate in hexanes) to yield the desired product (6.3 g, 46.6%) as a white solid; LC-MS (UV peak area, ESI) 90.7%, 287.2 [ ^MH⁺ ].

f) 5-Cyclopropyl-6-cyclopropylmethoxy-pyrazine-2-carboxylic acid methyl ester

5-Bromo-6-cyclopropylmethoxy-pyrazine-2-carboxylic acid methyl ester (5 g, 17.42 mmol), tribasic potassium phosphate (12.9 g, 60.98 mmol) and palladium (II) acetate (389 mg, 1.74 μmol) were dissolved in toluene (45 mL) and water (5 mL) and the reaction mixture was degassed with argon for 15 minutes. Cyclopropylboronic acid (2.9 g, 34.84 mmol) and tricyclohexylphosphine (0.487 g, 1.74 mmol) were added and the reaction mixture was stirred at 60°C for 16 hours. The mixture was partitioned between water and ethyl acetate and the organic phase was washed with brine (100 mL), dried over _Na2SO4 , _filtered and concentrated in vacuo. The crude material was purified by chromatography (Combi-Flash, 80 g, 10%-15% ethyl acetate in hexanes) to give the desired product (2.6 g, 60.1%) as a white solid; LC-MS (UV peak area, ESI) 98.9%, 249.2 [MH ⁺ ].

g) 5-Cyclopropyl-6-cyclopropylmethoxy-pyrazine-2-carboxylic acid

To a solution of 5-cyclopropyl-6-cyclopropylmethoxy-pyrazine-2-carboxylic acid methyl ester (7 g, 28.23 mmol) in THF (20 mL) and _H₂O (10 mL) was added lithium hydroxide (1.54 g, 26.69 mmol) and the mixture was stirred at ambient temperature for 4.5 hours. The solvent was concentrated in vacuo and the residue was diluted with _H₂O (20 mL). The aqueous phase was acidified with hydrochloric acid (1 M, pH 2-3) and a solid separated. The solid was triturated with toluene (25 ml) and dried in vacuo to yield the title compound (5.3 g, 86.6%) as a white crystalline solid; LC-MS (UV peak area, ESI) 93.2%, 233.2 [MH-].

h)(5-Cyclopropyl-6-cyclopropylmethoxy-pyrazin-2-yl)-((R)-2-methyl-pyrrolidin-1-yl)-methanone

5-Cyclopropyl-6-cyclopropylmethoxy-pyrazine-2-carboxylic acid (50 mg, 0.21 mmol) was suspended in DMF (1.5 mL). Mukaiyama reagent (CAN 878-23-9, 117 mg, 0.42 mmol), DIEA (0.16 mL, 1.12 mmol), and (R)-2-methylpyrrolidine (CAN 41720-98-3; 15 mg, 0.17 mmol) were added and the reaction mixture was stirred at room temperature for 12 hours. The mixture was extracted with ethyl acetate and water; the organic phase was dried over _Na₂SO₄ , _filtered , and concentrated in vacuo. The crude material was purified by reverse phase preparative HPLC (Xterra-RP18, 10μ, 19x250 mm/acetonitrile/10 mM ammonium acetate in water) to give the desired product (15 mg, 64%) as a cream solid; LC-MS (UV peak area, ESI) 90.6%, 302.2 [MH ⁺ ].

Example 2

[6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazin-2-yl]-((R)-2-methyl-pyrrolidin-1-yl)-methanone

a) 5-(3,3-Difluoro-azetidin-1-yl)-pyrazine-2-carboxylic acid methyl ester

5-Chloro-pyrazine-2-carboxylic acid methyl ester (CAN 33332-25-1; 15 g, 86.92 mmol) was dissolved in dioxane (100 mL). To this solution was added 3,3-difluoroazetidine hydrochloride (CAN 288315-03-7; 13.51 g, 104.31 mmol) and triethylamine (31.3 mL, 226 mmol). The mixture was stirred at 45°C for 22 hours and then cooled to room temperature. Brine (100 mL) was added and the mixture was extracted with ethyl acetate. The organic phase was washed sequentially with sodium bicarbonate solution (10%, 300 mL) and brine (200 mL); dried _{over Na2SO4} , filtered, and concentrated in vacuo. The crude material was purified by flash chromatography (silica gel, 200 g, 30% to 50% ethyl acetate in hexanes) to give the desired product (15 g, 75.3%) as a white solid; LC-MS (UV peak area, ESI) 98.6%, 230.4 [MH ⁺ ].

b) 6-Bromo-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carboxylic acid methyl ester

To a solution of 5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carboxylic acid methyl ester (16.5 g, 72.05 mmol) in chloroform (200 mL) was added portionwise N-bromosuccinimide (25.64 g, 151.34 mmol) at 60° C., and the mixture was stirred at 60° C. for 20 hours. After cooling, water (400 mL) was added and the organic phase was separated. The organic phase was washed successively with water (200 mL), brine (200 mL), dried over Na ₂ SO ₄ , filtered, and concentrated in vacuo. The crude material was purified by flash chromatography (silica gel, 200 g, 50% ethyl acetate in hexanes) to give the desired product (17 g, 77.2%) as a light yellow solid; LC-MS (UV peak area, ESI) 97.8%, 308.0 [MH ⁺ ].

c) 6-Bromo-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carboxylic acid

To a solution of 6-bromo-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carboxylic acid methyl ester (6.0 g, 19.48 mmol) in THF (20 mL) and _H₂O (10 mL) was added lithium hydroxide (1.06 g, 25.32 mmol) and the mixture was stirred at ambient temperature for 5 hours. The solvent was concentrated in vacuo and the residue was diluted with _H₂O (30 mL). The aqueous phase was acidified with hydrochloric acid (1 M, pH ~2-3) and the solid was isolated. The solid was triturated with toluene (25 mL) and dried in vacuo to yield the title compound (4.0 g, 70.2%) as a white crystalline solid; LC-MS (UV peak area, ESI) 100%, 294.2 [ ^MH⁺ ].

d) 6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carboxylic acid

To a solution of cyclopropyl-methanol (4.96 mL, 61.21 mmol) in anhydrous DMSO (90 mL) was added potassium hydroxide (5.89 g, 107.12 mmol) portionwise at ambient temperature. To this mixture was added a solution of 6-bromo-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carboxylic acid (9.0 g, 30.61 mmol) in DMSO (10 mL). The reaction mixture was stirred at ambient temperature for 3 hours. Water (100 mL) was added and the aqueous phase was acidified with aqueous hydrochloric acid (10%, pH ~ 3-4), and the solid was filtered. The solid was triturated with toluene (50 mL) and dried in vacuo to produce the title compound (8.0 g, 91.6%) as a white crystalline solid; LC-MS (UV peak area, ESI) 100%, 286.2 [MH ⁺ ].

e) [6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazin-2-yl]-((R)-2-methyl-pyrrolidin-1-yl)-methanone

The title compound was synthesized in analogy to Example 1h using 6-cyclopropyl-methoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carboxylic acid (Example 2d, 50 mg, 0.17 mmol) and (R)-2-methylpyrrolidine (CAN 41720-98-3; 15 mg, 0.17 mmol) as starting materials, and the title compound was isolated (25 mg, 40.4%) as a cream-colored solid; LC-MS (UV peak area, ESI) 98.42%, 431.0 [MH ⁺ ].

Example 3

6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carboxylic acid tert-butyl-(2-methoxy-ethyl)-amide

The title compound was synthesized in analogy to Example 1h using 6-cyclopropyl-methoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carboxylic acid (Example 2d, 50 mg, 0.17 mmol) and tert-butyl-(2-methoxy-ethyl)-amine (CAN 22687-22-5; 20 mg, 0.14 mmol) as starting materials and isolated (35 mg, 69.9%) as a cream-colored solid; LC-MS (UV peak area, ESI) 100%, 399.2 [MH ⁺ ].

Example 4

[6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazin-2-yl]-(3,3-dimethyl-morpholin-4-yl)-methanone

The title compound was synthesized in analogy to Example 1h using 6-cyclopropyl-methoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carboxylic acid (Example 2d, 50 mg, 0.17 mmol) and 3,3-dimethylmorpholine hydrochloride (CAN 59229-63-9; 22 mg, 0.14 mmol) as starting materials, and the title compound was isolated (50 mg, 67.08%) as a white solid; LC-MS (UV peak area, ESI) 93.6%, 383.2 [MH ⁺ ].

Example 5

[6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazin-2-yl]-((S)-2-methyl-pyrrolidin-1-yl)-methanone

The title compound was synthesized in analogy to Example 1h using 6-cyclopropyl-methoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carboxylic acid (Example 2d, 100 mg, 0.35 mmol) and (S)-2-methylpyrrolidine (CAN 59335-84-1; 25 mg, 0.28 mmol) as starting materials, and the title compound was isolated (74 mg, 59.9%) as a white solid; LC-MS (UV peak area, ESI) 99.5%, 353.0 [MH ⁺ ].

Example 6

[6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazin-2-yl]-2-oxa-5-aza-bicyclo[2.2.1]hept-5-yl-methanone

The title compound was synthesized in analogy to Example 1h using 6-cyclopropyl-methoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carboxylic acid (Example 2d, 50 mg, 0.17 mmol) and 2-oxa-5-aza-bicyclo[2.2.1]heptane (CAN 909186-56-7; 20 mg, 0.17 mmol) as starting materials and isolated (60 mg, 59.9%) as a cream solid; LC-MS (UV peak area, ESI) 93.0%, 367.0 [MH ⁺ ].

Example 7

6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carboxylic acid tert-butyl-methyl-amide

The title compound was synthesized in analogy to Example 1h using 6-cyclopropyl-methoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carboxylic acid (Example 2d, 50 mg, 0.17 mmol) and N-tert-butyl-methylamine (CAN 14610-37-8; 25 mg, 0.26 mmol) as starting materials, and the title compound was isolated (46 mg, 74.1%) as a milky white solid; LC-MS (UV peak area, ESI) 93.8%, 355.2 [MH ⁺ ].

Example 8

[6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazin-2-yl]-(3,3-difluoro-pyrrolidin-1-yl)-methanone

The title compound was synthesized in analogy to Example 1h using 6-cyclopropyl-methoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carboxylic acid (Example 2d, 50 mg, 0.17 mmol) and 3,3-difluoro-pyrrolidine hydrochloride (CAN163457-23-6; 37 mg, 0.26 mmol) as starting materials, and the title compound was isolated (30 mg, 46.1%) as a colorless sticky solid; LC-MS (UV peak area, ESI) 99.8%, 375.2 [MH ⁺ ].

Example 9

6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carboxylic acid ethyl-isopropyl-amide

The title compound was synthesized in analogy to Example 1h using 6-cyclopropyl-methoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carboxylic acid (Example 2d, 19.4 mg, 68 μmol) and N-ethyl-2-propylamine (CAN 19961-27-4; 8.2 μL, 68 μmol) as starting materials, and the title compound was isolated (16.8 mg, 70%) as a yellow oil; LC-MS (UV peak area, ESI) 99.8%, 375.2 [MH ⁺ ].

Example 10

[6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazin-2-yl]-(7-oxa-4-aza-spiro[2.5]octan-4-yl)-methanone

The title compound was synthesized in analogy to Example 1h using 6-cyclopropyl-methoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carboxylic acid (Example 2d, 50 mg, 0.17 mmol) and 7-oxa-4-azaspiro[2.5]octane (CAN218595-22-3; 17 mg, 0.14 mmol) as starting materials and isolated (45 mg, 67.4%) as a colorless sticky solid; LC-MS (UV peak area, ESI) 100%, 380.8 [M°C ⁺ ].

Example 11

{tert-Butyl-[6-cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carbonyl]-amino}-acetic acid ethyl ester

The title compound was synthesized in analogy to Example 1h using 6-cyclopropyl-methoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carboxylic acid (Example 2d, 100 mg, 0.35 mmol) and tert-butylamino-acetic acid ethyl ester (CAN37885-76-0; 45 mg, 0.28 mmol) as starting materials, and the title compound was isolated (50 mg, 33.4%) as a colorless viscous liquid; LC-MS (UV peak area, ESI) 100%, 427.0 [MH ⁺ ].

Example 12

6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carboxylic acid (2-methoxy-1,1-dimethyl-ethyl)-methyl-amide

The title compound was synthesized in analogy to Example 1h using 6-cyclopropyl-methoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carboxylic acid (Example 2d, 100 mg, 0.35 mmol) and (2-methoxy-1,1-dimethyl-ethyl)-methyl-amine (CAN 1177316-77-6; 43 mg, 0.28 mmol) as starting materials, and the title compound was isolated (70 mg, 52%) as a colorless viscous liquid; LC-MS (UV peak area, ESI) 99.8%, 384.8 [MH ⁺ ].

Example 13

[6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazin-2-yl]-(2,2-dimethyl-morpholin-4-yl)-methanone

The title compound was synthesized in analogy to Example 1h using 6-cyclopropyl-methoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carboxylic acid (Example 2d, 100 mg, 0.35 mmol) and 2,2-dimethylmorpholine (CAN 147688-58-2; 33 mg, 0.28 mmol) as starting materials, and the title compound was isolated (60 mg, 44.7%) as a white solid; LC-MS (UV peak area, ESI) 100%, 382.8 [MH ⁺ ].

Example 14

5-Cyclopropyl-6-cyclopropylmethoxy-pyrazine-2-carboxylic acid (2-methoxy-1,1-dimethyl-ethyl)-methyl-amide

The title compound was synthesized in analogy to Example 1h using 5-cyclopropyl-6-cyclopropylmethoxy-pyrazine-2-carboxylic acid (Example 1g, 50 mg, 0.21 mmol) and (2-methoxy-1,1-dimethyl-ethyl)-methyl-amine (CAN 1177316-77-6; 37.44 mg, 0.32 mmol) as starting materials and isolated (30 mg, 42.1%) as a colorless viscous liquid; LC-MS (UV peak area, ESI) 100%, 334.0 [MH ⁺ ].

Example 15

(5-Cyclopropyl-6-cyclopropylmethoxy-pyrazin-2-yl)-(2,2-dimethyl-pyrrolidin-1-yl)-methanone

The title compound was synthesized in analogy to Example 1h using 5-cyclopropyl-6-cyclopropylmethoxy-pyrazine-2-carboxylic acid (Example 1g, 50 mg, 0.21 mmol) and 2,2-dimethylpyrrolidine (CAN 35018-15-6; 51 mg, 0.32 mmol) as starting materials, and the title compound was isolated (65 mg, 97.0%) as a colorless viscous liquid; LC-MS (UV peak area, ESI) 100%, 317 [MH ⁺ ].

Example 16

(S)-1-(5-Cyclopropyl-6-cyclopropylmethoxy-pyrazine-2-carbonyl)-pyrrolidine-2-carboxylic acid methyl ester

The title compound was synthesized in analogy to Example 1h using 5-cyclopropyl-6-cyclopropylmethoxy-pyrazine-2-carboxylic acid (Example 1g, 50 mg, 0.21 mmol) and (S)-pyrrolidine-2-carboxylic acid methyl ester (CAN 43041-12-9; 42 mg, 0.32 mmol) as starting materials, and the title compound was isolated (26 mg, 35.6%) as a colorless viscous liquid; LC-MS (UV peak area, ESI) 100%, 345.8 [MH ⁺ ].

Example 17

(5-Cyclopropyl-6-cyclopropylmethoxy-pyrazin-2-yl)-(7-oxa-4-aza-spiro[2.5]octan-4-yl)-methanone

The title compound was synthesized in analogy to Example 1h using 5-cyclopropyl-6-cyclopropylmethoxy-pyrazine-2-carboxylic acid (Example 1g, 50 mg, 0.21 mmol) and 7-oxa-4-azaspiro[2.5]octane (CAN 126616-59-9; 36.2 mg, 0.32 mmol) as starting materials, and the title compound was isolated (55 mg, 78.5%) as a colorless viscous liquid; LC-MS (UV peak area, ESI) 100%, 330.2 [MH ⁺ ].

Example 18

(S)-1-(5-Cyclopropyl-6-cyclopropylmethoxy-pyrazine-2-carbonyl)-4,4-difluoro-pyrrolidine-2-carboxylic acid amide

The title compound was synthesized in analogy to Example 1h using 5-cyclopropyl-6-cyclopropylmethoxy-pyrazine-2-carboxylic acid (Example 1g, 50 mg, 0.21 mmol) and (2S)-4,4-difluoro-2-pyrrolidinecarboxamide hydrochloride (1:1) (CAN 426844-51-1; 43.8 mg, 0.24 mmol) as starting materials, and the title compound was isolated (62 mg, 79%) as a light yellow solid; LC-MS (UV peak area, ESI) 100%, 411.1486 [M+HCOO ⁺ ].

Example 19

(S)-1-[6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carbonyl]-4,4-difluoro-pyrrolidine-2-carboxylic acid amide

The title compound was synthesized in analogy to Example 1h using 6-cyclopropyl-methoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carboxylic acid (Example 2d, 50 mg, 0.17 mmol) and (2S)-4,4-difluoro-2-pyrrolidinecarboxamide hydrochloride (1:1) (CAN 426844-51-1; 36 mg, 0.19 mmol) as starting materials and isolated (29 mg, 40%) as a cream-colored solid; LC-MS (UV peak area, ESI) 100%, 418.1504 [MH ⁺ ].

Example 20

[6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazin-2-yl]-[4-(2-hydroxy-ethyl)-piperazin-1-yl]-methanone

The title compound was synthesized in analogy to Example 1h using 6-cyclopropyl-methoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carboxylic acid (Example 2d, 50 mg, 0.17 mmol) and 2-piperazin-1-yl-ethanol (CAN 103-76-4; 18.27 mg, 0.14 mmol) as starting materials and isolated (22 mg, 31.6%) as a cream solid; LC-MS (UV peak area, ESI) 100%, 398.2 [MH ⁺ ].

Example 21

[6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazin-2-yl]-(2,2-dimethyl-pyrrolidin-1-yl)-methanone

The title compound was synthesized in analogy to Example 1h using 6-cyclopropyl-methoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carboxylic acid (Example 2d, 50 mg, 0.17 mmol) and 2,2-dimethylpyrrolidine (CAN 35018-15-6; 15 mg, 0.17 mmol) as starting materials, and the title compound was isolated (42 mg, 65.6%) as a milky white solid; LC-MS (UV peak area, ESI) 99.5%, 367.2 [MH ⁺ ].

Example 22

(R)-1-[6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carbonyl]-pyrrolidine-2-carboxylic acid methyl ester

The title compound was synthesized in analogy to Example 1h using 6-cyclopropyl-methoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carboxylic acid (Example 2d, 50 mg, 0.17 mmol) and (R)-pyrrolidine-2-carboxylic acid methyl ester (CAN2577-48-2; 22 mg, 0.17 mmol) as starting materials, and the title compound was isolated (32 mg, 46.3%) as a milky white solid; LC-MS (UV peak area, ESI) 100%, 397.2 [MH ⁺ ].

Example 23

4-[6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carbonyl]-morpholin-2-one

The title compound was synthesized in analogy to Example 1h using 6-cyclopropyl-methoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carboxylic acid (Example 2d, 50 mg, 0.17 mmol) and morpholin-2-one (CAN 4441-15-0; 18 mg, 0.17 mmol) as starting materials and isolated (4 mg, 4.68%) as a cream-colored solid; LC-MS (UV peak area, ESI) 100%, 369.2 [MH ⁺ ].

Example 24

(R)-1-[6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carbonyl]-pyrrolidine-2-carboxylic acid dimethylamide

The title compound was synthesized in analogy to Example 1h using 6-cyclopropyl-methoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carboxylic acid (Example 2d, 50 mg, 0.17 mmol) and (R)-pyrrolidine-2-carboxylic acid dimethylamide (27 mg, 0.17 mmol) as starting materials, and the title compound was isolated (19 mg, 25.6%) as a milky white solid; LC-MS (UV peak area, ESI) 100%, 426.2 [MH ⁺ ].

Example 25

Acetate 1-(5-cyclopropyl-6-cyclopropylmethoxy-pyrazine-2-carbonyl)-3-methyl-pyrrolidin-3-yl ester

The title compound was synthesized in analogy to Example 1h using 5-cyclopropyl-6-cyclopropylmethoxy-pyrazine-2-carboxylic acid (Example 1g, 50 mg, 0.21 mmol) and 3-methyl-pyrrolidin-3-yl acetate (30 mg, 0.21 mmol) as starting materials, and the title compound was isolated (30 mg, 40%) as a milky white sticky solid; LC-MS (UV peak area, ESI) 100%, 359.8 [MH ⁺ ].

Example 26

(5-Cyclopropyl-6-cyclopropylmethoxy-pyrazin-2-yl)-(3,3,4,4-tetrafluoro-pyrrolidin-1-yl)-methanone

The title compound was synthesized in analogy to Example 1h using 5-cyclopropyl-6-cyclopropylmethoxy-pyrazine-2-carboxylic acid (Example 1g, 50 mg, 0.21 mmol) and 3,3,4,4-tetrafluoro-pyrrolidine (CAN 1810-13-5; 30 mg, 0.21 mmol) as starting materials, and the title compound was isolated (50 mg, 65.8%) as a milky white sticky solid; LC-MS (UV peak area, ESI) 93.20%, 360.2 [MH ⁺ ].

Example 27

Acetic acid (S)-1-[6-cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carbonyl]-pyrrolidin-3-yl ester

The title compound was synthesized in analogy to Example 1h using 6-cyclopropyl-methoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carboxylic acid (Example 2d, 50 mg, 0.17 mmol) and (S)-pyrrolidin-3-yl acetate (21.93 mg, 0.17 mmol) as starting materials, and the title compound was isolated (40 mg, 57.8%) as a milky white sticky solid; LC-MS (UV peak area, ESI) 100%, 397.0 [MH ⁺ ].

Example 28

[6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazin-2-yl]-(2-oxa-6-aza-spiro[3.4]octan-6-yl)-methanone

The title compound was synthesized in analogy to Example 1h using 6-cyclopropyl-methoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carboxylic acid (Example 2d, 50 mg, 0.17 mmol) and 2-oxa-6-aza-spiro[3.4]octane (CAN 220290-68-6; 20 mg, 0.17 mmol) as starting materials and isolated (25 mg, 37.8%) as a milky white sticky solid; LC-MS (UV peak area, ESI) 99.8%, 381.0 [MH ⁺ ].

Example 29

Acetic acid 1-[6-cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carbonyl]-3-methyl-pyrrolidin-3-yl ester

The title compound was synthesized in analogy to Example 1h using 6-cyclopropyl-methoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carboxylic acid (Example 2d, 50 mg, 0.17 mmol) and acetic acid 3-methyl-pyrrolidin-3-yl ester (25 mg, 0.17 mmol) as starting materials, and the title compound was isolated (20 mg, 28.2%) as a cream solid; LC-MS (UV peak area, ESI) 100%, 411.2 [MH ⁺ ].

Example 30

[6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazin-2-yl]-(3,3,4,4-tetrafluoro-pyrrolidin-1-yl)-methanone

The title compound was synthesized in analogy to Example 1h using 6-cyclopropyl-methoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carboxylic acid (Example 2d, 50 mg, 0.17 mmol) and 3,3,4,4-tetrafluoro-pyrrolidine (CAN1810-13-5; 30 mg, 0.21 mmol) as starting materials, and the title compound was isolated (45 mg, 60%) as a milky white solid; LC-MS (UV peak area, ESI) 99.4%, 411.4 [MH ⁺ ].

Example 31

5-(3,3-Difluoro-azetidin-1-yl)-6-(2,2,2-trifluoro-ethoxy)-pyrazine-2-carboxylic acid tert-butyl-methyl-amide

a) 5-(3,3-Difluoro-azetidin-1-yl)-6-(2,2,2-trifluoro-ethoxy)-pyrazine-2-carboxylic acid

To a solution of 2,2,2-trifluoroethanol (0.496 mL, 6.8 mmol) in anhydrous DMSO (12 mL) was added potassium hydroxide (0.668 g, 11.9 mmol) followed by 6-bromo-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carboxylic acid (1.0 g, 3.4 mmol) at ambient temperature. The reaction mixture was stirred at ambient temperature for 1.5 hours. Water (100 mL) was added, the mixture was acidified with aqueous hydrochloric acid (10%, pH 3-4) and extracted with ethyl acetate. The organic phases were washed with water, combined, dried over Na ₂ SO ₄ , filtered and concentrated. The solid was crystallized from ethyl acetate by adding heptane and dried in vacuo to yield the title compound (0.96 g, 90.1%) as a white crystalline solid; LC-MS (UV peak area, ESI) 91%, 312.0417 [MH ⁻ ].

b) 5-(3,3-Difluoro-azetidin-1-yl)-6-(2,2,2-trifluoro-ethoxy)-pyrazine-2-carboxylic acid tert-butyl-methyl-amide

The title compound was synthesized in analogy to Example 1h using 5-(3,3-difluoro-azetidin-1-yl)-6-(2,2,2-trifluoro-ethoxy)-pyrazine-2-carboxylic acid (Example 31a, 40 mg, 0.128 mmol) and N,2-dimethyl-2-propylamine (CAN 14610-37-8; 16.9 μL, 0.140 mmol) as starting materials and isolated (48 mg, 98%) as a white solid; LC-MS (UV peak area, ESI) 91%, 383.1519 [MH+].

Example 32

[5-(3,3-Difluoro-azetidin-1-yl)-6-(2,2,2-trifluoro-ethoxy)-pyrazin-2-yl]-(2,2-dimethyl-pyrrolidin-1-yl)-methanone

The title compound was synthesized in analogy to Example 1h using 5-(3,3-difluoro-azetidin-1-yl)-6-(2,2,2-trifluoro-ethoxy)-pyrazine-2-carboxylic acid (Example 31a, 40 mg, 0.128 mmol) and 2,2-dimethylpyrrolidine (CAN35018-15-6; 14 mg, 0.140 mmol) as starting materials and isolated (49 mg, 97%) as a white solid; LC-MS (UV peak area, ESI) 91%, 395.1507 [MH ⁺ ].

Example 33

1-[6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carbonyl]-piperidine-2-carboxylic acid amide

The title compound was synthesized in analogy to Example 1h using 6-cyclopropyl-methoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carboxylic acid (Example 2d, 100 mg, 0.351 mmol) and 2-piperidinecarboxamide (CAN 19889-77-1; 49.4 mg, 0.368 mmol) as starting materials, and the title compound was isolated (120 mg, 87%) as a light yellow solid; LC-MS (UV peak area, ESI) 100%, 396.1851 [MH ⁺ ].

Example 34

1-(5-Cyclopropyl-6-cyclopropylmethoxy-pyrazine-2-carbonyl)-4,4-dimethyl-pyrrolidine-2-carboxylic acid amide

a) 4,4-Dimethyl-pyrrolidine-1,2-dicarboxylic acid 1-tert-butyl ester

To a solution of 4,4-dimethyl-proline (1.7 g, 11.8 mmol) in anhydrous dioxane (29 mL) and water (24 mL) was added 1 N sodium hydroxide solution (9 mL) at ambient temperature, followed by the slow addition of di-tert-butyl dicarbonate (1.80 g, 8.2 mmol) dissolved in dioxane (5 mL). Additional 1 N sodium hydroxide solution (3 mL) was added and the mixture was stirred overnight. Additional di-tert-butyl dicarbonate (1.80 g, 8.2 mmol) dissolved in dioxane (5 mL) was added and stirring continued for 3 hours. The mixture was concentrated, 1 N sodium bisulfite solution (22 mL) was added and the suspension was extracted with ethyl acetate. The organic phases were washed with water and brine, combined, dried over _MgSO₄ , filtered and concentrated. The solid was crystallized from diethyl ether by the addition of heptane and dried in vacuo to yield the title compound (2.54 g, 89%) as a white crystalline solid; MS (ESI) 242.0 [MH-].

b) 4,4-Dimethyl-pyrrolidine-1,2-dicarboxylic acid 1-tert-butyl 2-(2,5-dioxo-pyrrolidin-1-yl) ester

A solution of 1-tert-butyl 4,4-dimethyl-pyrrolidine-1,2-dicarboxylate (2.0 g, 8.22 mmol) in THF (20 mL) was cooled to 0°C. To the cooled solution were added N-hydroxysuccinimide (1.2 g, 10.4 mmol) and diisopropylcarbodiimide (1.32 g, 10.4 mmol). The cooling was removed and the mixture was stirred at room temperature for 3 hours. The urea was filtered off, washed with diethyl ether and the filtrate was concentrated. The residue was partitioned between ethyl acetate and cold water; the organic phases were washed with cold brine, combined, dried over _MgSO₄ , filtered and concentrated in vacuo. The residue was purified by flash chromatography (silica, heptane/ethyl acetate 9:1) to give the title compound (1.95 g, 70%) as a colorless oil; MS (ESI) 341.1 [ ^MH⁺ ].

b) 2-Carbamoyl-4,4-dimethyl-pyrrolidine-1-carboxylic acid tert-butyl ester

A solution of 1-tert-butyl 4,4-dimethyl-pyrrolidine-1,2-dicarboxylate 2-(2,5-dioxo-pyrrolidin-1-yl) ester (1.9 g, 5.58 mmol) in DCM (20 mL) was cooled to 0°C. Gaseous ammonia was bubbled through the cold solution for 15 minutes, and stirring was continued in the cold for 1 hour. The succinimide was filtered off, washed with DCM, and the filtrate was partitioned between ethyl acetate and cold brine; the organic _phases were combined, dried over _Na2SO4 , filtered, and concentrated in vacuo. The residue was purified by flash chromatography (silica, ethyl acetate) to give the title compound (1.33 g, 98%) as a colorless foam; MS (ESI) 243.1 [MH ⁺ ].

d) 4,4-Dimethyl-pyrrolidine-2-carboxylic acid amide hydrochloride

A solution of tert-butyl 2-carbamoyl-4,4-dimethyl-pyrrolidine-1-carboxylate (1.2 g, 4.95 mmol) in dioxane (5 mL) was cooled to 10°C. Hydrogen chloride dissolved in dioxane (10 mL, 6.4 N) was added and the mixture was stirred for 1.5 hours. Diethyl ether (50 mL) was added to completely precipitate the product, which was filtered and dried to yield the title compound (0.84 g, 95%) as a colorless solid; MS (ESI) 143.0 [MH ⁺ ].

e) 1-(5-Cyclopropyl-6-cyclopropylmethoxy-pyrazine-2-carbonyl)-4,4-dimethyl-pyrrolidine-2-carboxylic acid amide

The title compound was synthesized in analogy to Example 1h using 5-cyclopropyl-6-cyclopropylmethoxy-pyrazine-2-carboxylic acid (Example 1g, 100 mg, 0.427 mmol) and 4,4-dimethyl-pyrrolidine-2-carboxylic acid amide hydrochloride (Example 34d; 83.9 mg, 0.47 mmol) as starting materials, and the title compound was isolated (142 mg, 93%) as a light yellow foam; LC-MS (UV peak area, ESI) 100%, 359.2085 [MH ⁺ ].

Example 35

1-[6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carbonyl]-4,4-dimethyl-pyrrolidine-2-carboxylic acid amide

The title compound was synthesized in analogy to Example 1h using 6-cyclopropyl-methoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carboxylic acid (Example 2d, 100 mg, 0.351 mmol) and 4,4-dimethyl-pyrrolidine-2-carboxylic acid amide hydrochloride (Example 34d; 68.9 mg, 0.386 mmol) as starting materials and isolated (133 mg, 93%) as a white foam; LC-MS (UV peak area, ESI) 100%, 410.2004 [MH ⁺ ].

Example 36

(-)-1-[6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carbonyl]-piperidine-2-carboxylic acid amide

The enantiomers of 1-[6-cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carbonyl]-piperidine-2-carboxylic acid amide (Example 33) were separated by chiral HPLC (Reprosil Chiral NR, 30% ethanol in n-heptane). The (-) enantiomer (48 mg, 44%) was isolated as a white solid; LC-MS (UV peak area/ESI) 100%, 396.1842 [ ^{MH +} ]; (-) enantiomer, ∼96% ee;

Example 37

(-)-4-[6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carbonyl]-thiomorpholine-3-carboxylic acid amide

a) 4-[6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carbonyl]-thiomorpholine-3-carboxylic acid amide

The title compound was synthesized in analogy to Example 1h using 6-cyclopropyl-methoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carboxylic acid (Example 2d, 100 mg, 0.351 mmol) and 3-thiomorpholinecarboxamide (CAN103742-31-0; 56.4 mg, 0.386 mmol) as starting materials, and the title compound was isolated (140 mg, 97%) as a cream-colored solid; LC-MS (UV peak area, ESI) 100%, 414.1411 [MH ⁺ ].

b) (-)-4-[6-cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carbonyl]-thiomorpholine-3-carboxylic acid amide

The enantiomers of 4-[6-cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carbonyl]-thiomorpholine-3-carboxylic acid amide (Example 37a) were separated by chiral HPLC (Reprosil Chiral NR, 30% ethanol in n-heptane). The (-) enantiomer (48 mg, 39%) was isolated as a light yellow solid; LC-MS (UV peak area/ESI) 100%, 414.1405 [MH ⁺ ]; (-) enantiomer, ˜100% ee;

Example 38

(-)-1-[6-Cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carbonyl]-4,4-dimethyl-pyrrolidine-2-carboxylic acid amide

The enantiomers of 1-[6-cyclopropylmethoxy-5-(3,3-difluoro-azetidin-1-yl)-pyrazine-2-carbonyl]-4,4-dimethyl-pyrrolidine-2-carboxylic acid amide (Example 35) were separated by chiral HPLC (Reprosil Chiral NR, 20% ethanol in n-heptane). The (-) enantiomer (52 mg, 44%) was isolated as a white solid; LC-MS (UV peak area/ESI) 100%, 410.2003 [MH ⁺ ]; (-) enantiomer, ˜100% ee;

Example 39

(-)-1-(5-Cyclopropyl-6-cyclopropylmethoxy-pyrazine-2-carbonyl)-4,4-dimethyl-pyrrolidine-2-carboxylic acid amide

The enantiomers of 1-(5-cyclopropyl-6-cyclopropylmethoxy-pyrazine-2-carbonyl)-4,4-dimethyl-pyrrolidine-2-carboxylic acid amide (Example 34e) were separated by chiral HPLC (Reprosil Chiral NR, 20% ethanol in n-heptane). The (-) enantiomer (52 mg, 41%) was isolated as a white foam; LC-MS (UV peak area/ESI) 100%, 359.2082 [MH ⁺ ]; (-) enantiomer, ∼99% ee;

Example 40

(±)-5-[6-(Cyclopropylmethoxy)-5-(3,3-difluoroazetidin-1-yl)pyrazine-2-carbonyl]-5-azaspiro[2.4]heptane-6-carboxamide

a)(±)-tert-Butyl 6-carbamoyl-5-azaspiro[2.4]heptane-5-carboxylate

Carbonyldiimidazole (211 mg, 1.3 mmol) was added to an ice-cold solution of (±)-5-(tert-butoxycarbonyl)-5-azaspiro[2.4]heptane-6-carboxylic acid (CAN 1454843-77-6, 112 mg, 464 μmol) in DMF (1 mL). The reaction mixture was warmed to ambient temperature and continued to stir for 2 h. Under ice cooling, NH ₃ gas was bubbled through the reaction mixture for 10 min. Stirring was continued at ambient temperature for 72 h. The reaction mixture was poured into 30 mL of ice/water and extracted with EtOAc (2 x 30 mL). The combined extracts were washed with ice/brine (20 mL), dried over Na ₂ SO ₄ and concentrated in vacuo to produce the title compound (54 mg, 48%) as a colorless oil, which was used in the next reaction step without further purification, MS (ESI) 141.1 [MH-Boc ⁺ ].

b) (±)-5-Azaspiro[2.4]heptane-6-carboxamide hydrochloride

A solution of (±)-tert-butyl 6-carbamoyl-5-azaspiro[2.4]heptane-5-carboxylate (Example 40a, 65 mg, 270 μmol) in 4M HCl in dioxane (1.4 mL) was stirred at ambient temperature for 4 h. The solvent was removed under reduced pressure to yield the title compound (55 mg, quantitative) as a light yellow oil, which was used in the next reaction step without further purification, LC-MS 141.1023 [MH ⁺ ].

c) (±)-5-[6-(cyclopropylmethoxy)-5-(3,3-difluoroazetidin-1-yl)pyrazine-2-carbonyl]-5-azaspiro[2.4]heptane-6-carboxamide

Under argon atmosphere, 2-bromo-1-ethylpyridine tetrafluoroborate (38.3 mg, 119 μ mol) is added to 6- (cyclopropylmethoxy) -5- (3,3- difluoroazetidine -1- base) pyrazine -2- carboxylic acid (embodiment 2d, 20 mg, 70.1 μ mol), (±) -5- azaspiro [2.4] heptane -6- carboxamide hydrochloride (embodiment 40b, 18.6 mg, 105 μ mol) and DIEA (34.1 mg, 45.2 μ L, 264 μ mol) in dioxane (150 μ L).Reactant mixture is stirred at ambient temperature for 1 day, poured into ice/0.1M NaOH (25 mL) and extracted with EtOAc (2x 25 mL).The combined extracts are washed to pH 6 with ice/0.1N HCl (25 mL) and frozen water/brine (25 mL). The organic layer was dried _{over Na2SO4} and filtered off.The solvent was removed under reduced pressure and the crude product was purified by preparative HPLC (ACN/HCOOH 98/2%, Gemini NX 3u) to yield the title compound (18 mg, 63%) as a cream solid, MS (ESI) 408.3 [MH ⁺ ].

Example 41

(2S)-1-[6-(Cyclopropylmethoxy)-5-(3,3-difluoroazetidin-1-yl)pyrazine-2-carbonyl]-4-hydroxy-4-methylpyrrolidine-2-carboxamide

a) (2S)-4-Hydroxy-4-methylpyrrolidine-2-carboxylic acid methyl ester hydrochloride

A solution of 1-tert-butyl 2-methyl (2S)-4-hydroxy-4-methylpyrrolidine-1,2-dicarboxylate (CAN 1367552-84-8, 466 mg, 1.8 mmol) in a 4M solution of hydrogen chloride in dioxane (8.99 mL, 36 mmol) was stirred at ambient temperature for 4 h. The solvent was removed under reduced pressure to yield the title compound (446 mg, quant.) as a brown solid, which was used in the next reaction step without further purification, MS (ESI) 160.1 [MH ⁺ ].

b) (2S)-4-Hydroxy-4-methylpyrrolidine-2-carboxamide hydrochloride

By (2S)-4-hydroxy-4-methylpyrrolidine-2-methyl-formiate hydrochloride (embodiment 41a, 446mg, 2.28mmol) in the methanol solution of 7M ammonia (6.51mL, 45.6mmol) solution in ambient temperature stirred 2 days.Reaction mixture is poured on frozen water (30mL) and extracted with EtOAc (2x 40mL).Water layer is concentrated in a vacuum.Residue is suspended in methanol and EtOAc.Solid is filtered off.After adding the dioxane solution (2mL) of 4M HCl, filtrate is concentrated in a vacuum, so as to produce title compound (550mg, quantitative), is brown solid, is used for next reaction step when it is not further purified, MS (ESI)144.1[MH ⁺ ].

c) (2S)-1-[6-(cyclopropylmethoxy)-5-(3,3-difluoroazetidin-1-yl)pyrazine-2-carbonyl]-4-hydroxy-4-methylpyrrolidine-2-carboxamide

In analogy to the procedure described in Example 40c, 6-(cyclopropylmethoxy)-5-(3,3-difluoroazetidin-1-yl)pyrazine-2-carboxylic acid (Example 2d, 50 mg, 175 μmol) was reacted with (2S)-4-hydroxy-4-methylpyrrolidine-2-carboxamide hydrochloride (Example 41b, 31.7 mg, 175 μmol) to give the title compound (12 mg, 13%) as a light yellow oil, MS (ESI) 412.3 [MH ⁺ ].

Example 42

(2S)-1-[5-(3,3-Difluoroazetidin-1-yl)-6-(2,2-difluoroethoxy)pyrazine-2-carbonyl]-4,4-difluoro-pyrrolidine-2-carboxamide

a) Methyl 5-(3,3-difluoroazetidin-1-yl)-6-(2,2-difluoroethoxy)pyrazine-2-carboxylate

Over 30 minutes, lithium 2-methylpropan-2-ol (3.39 mL, 7.47 mmol) was added to a solution of methyl 6-bromo-5-(3,3-difluoroazetidin-1-yl)pyrazine-2-carboxylate (CAN 1432507-18-0, 1 g, 3.25 mmol) and 2,2-difluoroethanol (CAN 359-13-7, 346 mg, 267 μL, 4.22 mmol) in DMF (6.67 mL) at ambient temperature. The reaction mixture was heated to 70° C. and stirred for 20 h. After cooling to ambient temperature, ice water (50 mL) and 2N HCl (8 mL) were added. A brown precipitate was formed, which was filtered off and purified by column chromatography to obtain the title compound (77 mg, 7%) as a light yellow solid; MS (ESI) m/e=310.1 [MH ⁺ ].

b) 5-(3,3-Difluoroazetidin-1-yl)-6-(2,2-difluoroethoxy)pyrazine-2-carboxylic acid

A solution of methyl 5-(3,3-difluoroazetidin-1-yl)-6-(2,2-difluoroethoxy)pyrazine-2-carboxylate (Example 42a, 77 mg, 249 μmol) and lithium hydroxide hydrate (12.5 mg, 299 μmol) in tetrahydrofuran (500 μL) and water (50 μL) was stirred at ambient temperature for 12 h. The reaction mixture was poured onto ice/0.1N HCl (1 x 25 mL) and extracted with EtOAc (2 x 25 mL). The combined extracts were washed with ice/brine (25 mL), dried over Na ₂ SO ₄ , filtered, and evaporated to dryness to yield the title compound (68 mg, 93%) as a creamy white solid; MS (ESI) m/e=296.1 [MH ⁺ ].

c) (2S)-1-[5-(3,3-Difluoroazetidin-1-yl)-6-(2,2-difluoroethoxy)pyrazine-2-carbonyl]-4,4-difluoro-pyrrolidine-2-carboxamide

2-Bromo-1-ethylpyridine tetrafluoroborate (46.2 mg, 144 μmol) was added to a solution of 5-(3,3-difluoroazetidine-1-yl)-6-(2,2-difluoroethoxy)pyrazine-2-carboxylic acid (Example 42 b, 25 mg, 84.7 μmol), (2S)-4,4-difluoro-2-pyrrolidinecarboxamide hydrochloride (CAN 426844-51-1, 19.0 mg, 102 μmol) and DIEA (41.0 mg, 54.4 μL, 318 μmol) in dioxane (500 μL). The reaction mixture was stirred at ambient temperature for 1 day, poured onto ice/0.1N HCl (1 x 25 mL) and extracted with EtOAc (2 x 25 mL). The combined extracts were washed with ice water/brine (1 _x 25 mL), dried over _Na2SO4 , filtered off and evaporated in vacuo. The crude product was crystallized from EtOAc and heptane to give the title compound (19 mg, 53%) as a cream solid; MS (ESI) m/e = 428.1161 [MH ⁺ ].

Example 43

Pharmacological tests

The following tests were performed to determine the activity of the compounds of formula I:

Radioligand binding assay

The affinity of the compounds of the invention for the cannabinoid CB1 receptor was determined using the recommended amount of membrane preparations (PerkinElmer) from human embryonic kidney (HEK) cells expressing the human CNR1 or CNR2 receptor, respectively, bound to 1.5 or 2.6 nM [3H]-CP-55,940 (Perkin Elmer) as a radioligand. Binding was performed in a total volume of 0.2 ml of binding buffer (50 mM Tris, 5 mM MgCl2, 2.5 mM EDTA, and 0.5% (wt/vol) fatty acid-free BSA, pH 7.4, for the CB1 receptor, and 50 mM Tris, 5 mM _MgCl2 , 2.5 mM EGTA, and 0.1% (wt/vol) fatty acid-free BSA, pH 7.4, for the CB2 receptor) with shaking at 30°C for 1 hour. The reaction was terminated by rapid filtration through a microfiltration plate coated with 0.5% polyethyleneimine (UniFilter GF/B filter plate; Packard). Bound radioactivity was analyzed using nonlinear regression analysis (Activity Base, ID Business Solutions, Limited) for Ki, and Kd values for [3H]CP55,940 were determined from saturation experiments. The compounds of formula (I) exhibited excellent affinity for the CB2 receptor, with an affinity of less than 10 μM, more particularly 1 nM to 3 μM, and most particularly 1 nM to 100 nM.

cAMP assay

CHO cells expressing human CB1 or CB2 receptors were seeded at 50,000 cells/well in black 96-well plates with clear flat bottoms (Corning Costar #3904) 17-24 hours prior to the experiment in DMEM (Invitrogen No. 31331) supplemented with 1x HT and 10% fetal bovine serum and incubated in a humidified incubator at 5% _CO2 and 37°C. The medium was exchanged with Krebs Ringer Bicarbonate buffer containing 1 mM IBMX and incubated at 30°C for 30 minutes. Compounds were added to a final assay volume of 100 μl and incubated at 30°C for 30 minutes. The cAMP-Nano-TRF detection kit (Roche Diagnostics) was used to terminate the assay by adding 50 μl of lysis reagent (Tris, NaCl, 1.5% Triton X100, 2.5% NP40, 10% _NaN3 ) and 50 μl of detection solution (20 μM mAb Alexa700-cAMP 1:1 and 48 μM Ruthenium-2-AHA-cAMP) and shaking for 2 h at room temperature. Time-resolved energy transfer was measured using a TRF reader (Evotec Technologies GmbH) equipped with an Nd:YAG laser as the excitation source. The plate was measured in duplicate, with excitation at 355 nm and emission at either 730 (30 nm bandwidth) or 645 nm (75 nm bandwidth) with a 100 ns delay and a 100 ns gate, respectively, for a total exposure time of 10 s. The FRET signal was calculated as follows: FRET = T730-Alexa730-P (T645-B645), P = Ru730-B730/Ru645-B645, where T730 is the test well measured at 730 nM, T645 is the test well measured at 645 nm, and B730 and B645 are buffer controls at 730 nm and 645 nm, respectively. cAMP levels were determined using a standard curve spanning from 10 μM to 0.13 nM cAMP.

_EC50 values were determined using the Activity Base assay (ID Business Solution, Limited). _EC50 values for a wide range of cannabinoid agonists generated from this assay were consistent with values published in the scientific literature.

The compounds of the invention are CB2 agonists with _EC50 below 0.5 μM and are at least 10-fold selective over CB1 in corresponding assays. Particular compounds of the invention are CB2 agonists with _EC50 below 0.05 μM and are at least 500-fold selective over CB1 in corresponding assays.

For example, the following compounds exhibited the following human _EC50 values in the functional cAMP assay described above:

Example 1 0.0573 >10 2 0.0049 >10

Example 3 0.004 >10 4 0.0043 >10 5 0.0817 >10 6 0.2569 >10 7 0.0032 >10 8 0.0298 >10 9 0.0199 >10 10 0.015 >10 11 0.0068 >10 12 0.0092 >10 13 0.0685 >10 14 0.0146 >10 15 0.0112 >10 16 0.1907 >10 17 0.1404 >10 18 0.0235 >10 19 0.0057 >10 20 0.3157 >10 twenty one 0.0043 >10 twenty two 0.2524 >10 twenty three 0.0184 >10 twenty four 0.3331 >10 25 0.1097 >10 26 0.1236 >10 27 0.2712 >10 28 0.2041 >10 29 0.0088 >10 30 0.0263 >10

Example 31 0.1296 >10 32 0.0812 >10 33 0.3296 >10 34 0.0016 >10 35 0.0115 >10 36 0.2167 >10 37 0.3083 >10 38 0.0014 >10 39 0.0103 >10 40 0.039 >10 41 0.090 >10 42 0.3097 >10

Example A

Film-coated tablets containing the following ingredients can be prepared in a conventional manner:

nuclear: Compound of formula (I) 10.0mg 200.0mg microcrystalline cellulose 23.5mg 43.5mg Lactose hydrate 60.0mg 70.0mg Povidone K30 12.5mg 15.0mg Sodium starch glycolate 12.5mg 17.0mg magnesium stearate 1.5mg 4.5mg (Nuclear weight) 120.0mg 350.0mg Film coating: Hydroxypropyl methylcellulose 3.5mg 7.0mg Polyethylene glycol 6000 0.8mg 1.6mg talc 1.3mg 2.6mg

Iron oxide (yellow) 0.8mg 1.6mg Titanium dioxide 0.8mg 1.6mg

The active ingredient is sieved and mixed with microcrystalline cellulose, and the mixture is granulated with an aqueous solution of polyvinylpyrrolidone. The granules are then mixed with sodium starch glycolate and magnesium stearate and compressed to yield kernels of 120 or 350 mg, respectively. The kernels are then coated with an aqueous solution/suspension of the film coating described above.

Example B

Capsules containing the following ingredients can be prepared in a conventional manner:

Compound of formula (I) 25.0mg lactose 150.0mg corn starch 20.0mg talc 5.0mg

The ingredients were sieved and mixed and filled into size 2 capsules.

Example C

The injection solution may have the following composition:

Compound of formula (I) 3.0mg polyethylene glycol 400 150.0mg Acetic acid Add enough water to obtain pH 5.0 Water for injection Add to 1.0ml

Dissolve the active ingredient in a mixture of polyethylene glycol 400 and water for injection (partial). Adjust the pH to 5.0 by adding acetic acid. Add the remainder of water to bring the volume to 1.0 ml. Filter the solution, fill into vials using an appropriate overdose, and sterilize.

Claims (11)

1. A compound of formula (I) or a medicinal salt thereof in ^R1 is a _C3-8 cycloalkyl _C1-8 alkoxy or a halo- _C1-8 alkoxy; ^R2 is a _C3-8 cycloalkyl or haloazinonyl butyl group; ^R3 and ^R4 are independently selected from _C1-8 alkyl, _C1-8 alkoxy, _C1-8 alkoxy- _C1-8 alkyl, and _C1-8 alkoxy-carbonyl- _C1-8 alkyl; Alternatively, ^R3 and ^R4 together with the nitrogen atom to which they are attached form a heterocyclic group or a substituted heterocyclic group, wherein the heterocyclic group is pyrrolidinyl, morpholinyl, oxomorpholinyl, 2-oxo-5-aza-bicyclo[2.2.1]heptyl, 7-oxa-4-aza-spiro[2.5]octyl, piperazine, 2-oxa-6-aza-spiro[3.4]octyl, thiomorpholinyl or 5-azaspiro[2.4]heptyl, and wherein the substituted heterocyclic group is a heterocyclic group substituted by one to four substituents independently selected from the following: _C1-8 alkyl, halogen, aminocarbonyl, hydroxy _C1-8 alkyl, _C1-8 alkoxycarbonyl, _C1-8 alkylthiocarbamoyl, _C1-8 alkylcarbonyloxy and hydroxy. 2. The compound according to claim 1, wherein ^R1 is a _{C3-8 cycloalkylC1-8} alkoxy group. 3. The compound according to claim 1 or 2, wherein R ¹ is cyclopropylmethoxy. 4. The compound according to claim 1 or 2, wherein ^R2 is cyclopropyl or difluoroazacyclobutyl. 5. The compound according to claim 1 or 2, wherein ^R3 and ^R4 are independently selected from _C1-8 alkyl, _C1-8 alkoxy and _C1-8 alkoxy- _C1-8 alkyl, or wherein ^R3 and ^R4 together with the nitrogen atom to which they are attached form a heterocyclic group or a substituted heterocyclic group, wherein the heterocyclic group is pyrrolidinyl, morpholinyl or 5-azaspiro[2.4]heptyl, and wherein the substituted heterocyclic group is a heterocyclic group substituted by one to three substituents independently selected from _C1-8 alkyl, halogen and aminocarbonyl. 6. The compound according to claim 1 or 2, wherein ^R3 and ^R4 are independently selected from methyl, tert-butyl, methoxyethyl or methoxybutyl, or wherein ^R3 and ^R4 together with the nitrogen atom to which they are attached form dimethylmorpholino, dimethylpyrrolidinyl, (aminocarbonyl)(difluoro)pyrrolidinyl, (aminocarbonyl)(dimethyl)pyrrolidinyl or (aminocarbonyl)5-azaspiro[2.4]heptyl. 7. Compounds selected from: (5-Cyclopropyl-6-Cyclopropylmethoxy-pyrazin-2-yl)-((R)-2-methyl-pyrrolidine-1-yl)-methyl ketone; [6-Cyclopropylmethoxy-5-(3,3-difluoro-azacyclobutane-1-yl)-pyrazin-2-yl]-((R)-2-methyl-pyrrolidine-1-yl)-methyl ketone; 6-Cyclopropylmethoxy-5-(3,3-difluoro-azacyclobutane-1-yl)-pyrazin-2-carboxylic acid tert-butyl-(2-methoxy-ethyl)-amide; [6-Cyclopropylmethoxy-5-(3,3-difluoro-azacyclobutane-1-yl)-pyrazin-2-yl]-(3,3-dimethyl-morpholin-4-yl)-methyl ketone; [6-Cyclopropylmethoxy-5-(3,3-difluoro-azacyclobutane-1-yl)-pyrazin-2-yl]-((S)-2-methyl-pyrrolidine-1-yl)-methyl ketone; [6-Cyclopropylmethoxy-5-(3,3-difluoro-azacyclobutane-1-yl)-pyrazin-2-yl]-(1R,4R)-2-oxa-5-aza-bicyclo[2.2.1]hept-5-yl methyl ketone; 6-Cyclopropylmethoxy-5-(3,3-difluoro-azacyclobutane-1-yl)-pyrazine-2-carboxylic acid tert-butyl-methyl-amide; [6-Cyclopropylmethoxy-5-(3,3-difluoro-azacyclobutane-1-yl)-pyrazin-2-yl]-(3,3-difluoro-pyrrolidine-1-yl)-methyl ketone; 6-Cyclopropylmethoxy-5-(3,3-difluoro-azacyclobutane-1-yl)-pyrazine-2-carboxylic acid ethyl-isopropyl-amide; [6-Cyclopropylmethoxy-5-(3,3-difluoro-azacyclobutane-1-yl)-pyrazin-2-yl]-(7-oxa-4-aza-spiro[2.5]oct-4-yl)-methyl ketone; {tert-butyl-[6-cyclopropylmethoxy-5-(3,3-difluoro-azacyclobutane-1-yl)-pyrazine-2-carbonyl]-amino}-ethyl acetate; 6-Cyclopropylmethoxy-5-(3,3-difluoro-azacyclobutane-1-yl)-pyrazin-2-carboxylic acid (2-methoxy-1,1-dimethyl-ethyl)-methyl-amide; [6-Cyclopropylmethoxy-5-(3,3-difluoro-azacyclobutane-1-yl)-pyrazin-2-yl]-(2,2-dimethyl-morpholin-4-yl)-methyl ketone; 5-Cyclopropyl-6-cyclopropylmethoxypyrazine-2-carboxylic acid (2-methoxy-1,1-dimethyl-ethyl)-methyl-amide; (5-Cyclopropyl-6-Cyclopropylmethoxy-pyrazin-2-yl)-(2,2-Dimethyl-pyrrolidone-1-yl)-methyl ketone; (S)-1-(5-cyclopropyl-6-cyclopropylmethoxy-pyrazine-2-carbonyl)-pyrrolidine-2-carboxylic acid methyl ester; (5-Cyclopropyl-6-Cyclopropylmethoxy-pyrazin-2-yl)-(7-oxa-4-aza-spiro[2.5]oct-4-yl)-methyl ketone; (S)-1-(5-cyclopropyl-6-cyclopropylmethoxy-pyrazine-2-carbonyl)-4,4-difluoro-pyrrolidine-2-carboxamide; (S)-1-[6-cyclopropylmethoxy-5-(3,3-difluoro-azacyclobutane-1-yl)-pyrazine-2-carbonyl]-4,4-difluoro-pyrrolidine-2-carboxamide; [6-Cyclopropylmethoxy-5-(3,3-difluoro-azacyclobutane-1-yl)-pyrazin-2-yl]-[4-(2-hydroxy-ethyl)-piperazin-1-yl]-methyl ketone; [6-Cyclopropylmethoxy-5-(3,3-difluoro-azacyclobutane-1-yl)-pyrazin-2-yl]-(2,2-dimethyl-pyrrolidone-1-yl)-methyl ketone; (R)-1-[6-cyclopropylmethoxy-5-(3,3-difluoro-azacyclobutane-1-yl)-pyrazine-2-carbonyl]-pyrrolidine-2-carboxylic acid methyl ester; 4-[6-cyclopropylmethoxy-5-(3,3-difluoro-azacyclobutane-1-yl)-pyrazin-2-carbonyl]-morpholin-2-one; (R)-1-[6-cyclopropylmethoxy-5-(3,3-difluoro-azacyclobutane-1-yl)-pyrazine-2-carbonyl]-pyrrolidine-2-thiocarboxylic acid dimethylamide; 1-(5-cyclopropyl-6-cyclopropylmethoxy-pyrazine-2-carbonyl)-3-methyl-pyrrolidine-3-yl ester of acetate; (5-Cyclopropyl-6-Cyclopropylmethoxy-pyrazin-2-yl)-(3,3,4,4-Tetrafluoro-pyrrolidine-1-yl)-methyl ketone; Acetic acid (S)-1-[6-cyclopropylmethoxy-5-(3,3-difluoro-azacyclobutane-1-yl)-pyrazin-2-carbonyl]-pyrrolidine-3-yl ester; [6-Cyclopropylmethoxy-5-(3,3-difluoro-azacyclobutane-1-yl)-pyrazin-2-yl]-(2-oxa-6-aza-spiro[3.4]oct-6-yl)-methyl ketone; 1-[6-cyclopropylmethoxy-5-(3,3-difluoro-azacyclobutane-1-yl)-pyrazine-2-carbonyl]-3-methyl-pyrrolidine-3-yl ester; [6-Cyclopropylmethoxy-5-(3,3-difluoro-azacyclobutane-1-yl)-pyrazin-2-yl]-(3,3,4,4-tetrafluoro-pyrrolidine-1-yl)-methyl ketone; 5-(3,3-difluoro-azacyclobutane-1-yl)-6-(2,2,2-trifluoro-ethoxy)-pyrazine-2-carboxylic acid tert-butyl-methyl-amide; [5-(3,3-difluoro-azacyclobutane-1-yl)-6-(2,2,2-trifluoro-ethoxy)-pyrazin-2-yl]-(2,2-dimethyl-pyrrolidone-1-yl)-methyl ketone; 1-(5-Cyclopropyl-6-Cyclopropylmethoxy-pyrazine-2-carbonyl)-4,4-Dimethyl-pyrrolidine-2-carboxamide; 1-[6-Cyclopropylmethoxy-5-(3,3-difluoro-azacyclobutane-1-yl)-pyrazine-2-carbonyl]-4,4-dimethyl-pyrrolidine-2-carboxamide; (-)-4-[6-cyclopropylmethoxy-5-(3,3-difluoro-azacyclobutane-1-yl)-pyrazine-2-carbonyl]-thiomorpholine-3-carboxamide; (-)-1-[6-Cyclopropylmethoxy-5-(3,3-difluoro-azacyclobutane-1-yl)-pyrazine-2-carbonyl]-4,4-dimethyl-pyrrolidine-2-carboxamide; (-)-1-(5-Cyclopropyl-6-Cyclopropylmethoxy-pyrazine-2-carbonyl)-4,4-Dimethyl-pyrrolidine-2-carboxamide; (±)-5-[6-(cyclopropylmethoxy)-5-(3,3-difluoroazacyclobutane-1-yl)pyrazine-2-carbonyl]-5-azaspiro[2,4]heptane-6-carboxamide; (2S)-1-[6-(cyclopropylmethoxy)-5-(3,3-difluoroazacyclobutane-1-yl)pyrazin-2-carbonyl]-4-hydroxy-4-methylpyrrolidine-2-carboxamide; and (2S)-1-[5-(3,3-difluoroazacyclobutane-1-yl)-6-(2,2-difluoroethoxy)pyrazine-2-carbonyl]-4,4-difluoro-pyrrolidine-2-carboxamide. 8. Compounds selected from: 6-Cyclopropylmethoxy-5-(3,3-difluoro-azacyclobutane-1-yl)-pyrazin-2-carboxylic acid tert-butyl-(2-methoxy-ethyl)-amide; [6-Cyclopropylmethoxy-5-(3,3-difluoro-azacyclobutane-1-yl)-pyrazin-2-yl]-(3,3-dimethyl-morpholin-4-yl)-methyl ketone; 6-Cyclopropylmethoxy-5-(3,3-difluoro-azacyclobutane-1-yl)-pyrazine-2-carboxylic acid tert-butyl-methyl-amide; 6-Cyclopropylmethoxy-5-(3,3-difluoro-azacyclobutane-1-yl)-pyrazin-2-carboxylic acid (2-methoxy-1,1-dimethyl-ethyl)-methyl-amide; (5-Cyclopropyl-6-Cyclopropylmethoxy-pyrazin-2-yl)-(2,2-Dimethyl-pyrrolidone-1-yl)-methyl ketone; (S)-1-[6-cyclopropylmethoxy-5-(3,3-difluoro-azacyclobutane-1-yl)-pyrazine-2-carbonyl]-4,4-difluoro-pyrrolidine-2-carboxamide; [6-Cyclopropylmethoxy-5-(3,3-difluoro-azacyclobutane-1-yl)-pyrazin-2-yl]-(2,2-dimethyl-pyrrolidone-1-yl)-methyl ketone; 1-(5-Cyclopropyl-6-Cyclopropylmethoxy-pyrazine-2-carbonyl)-4,4-Dimethyl-pyrrolidine-2-carboxamide; (-)-1-[6-cyclopropylmethoxy-5-(3,3-difluoro-azacyclobutane-1-yl)-pyrazin-2-carbonyl]-4,4-dimethyl-pyrrolidine-2-carboxamide; and (±)-5-[6-(cyclopropylmethoxy)-5-(3,3-difluoroazacyclobutane-1-yl)pyrazine-2-carbonyl]-5-azaspiro[2.4]heptane-6-carboxamide. 9. A method for preparing a compound according to any one of claims 1 to 8, the method comprising reacting a compound of formula (II) in the presence of NHR ^{3R 4} , an amide coupling agent, and a base. ^R1 to ^R4 are defined as in any one of claims 1 to 8. 10. A pharmaceutical composition comprising the compound according to any one of claims 1 to 8 and a therapeutically inert carrier. 11. Use of the compound according to any one of claims 1 to 8 in the preparation of a medicament for the treatment or prevention of pain, atherosclerosis, age-related macular degeneration, diabetic retinopathy, glaucoma, retinal vein occlusion, retinopathy of prematurity, ocular ischemia syndrome, geographic atrophy, diabetes, inflammation, inflammatory bowel disease, ischemia-reperfusion injury, acute liver failure, liver fibrosis, pulmonary fibrosis, renal fibrosis, systemic fibrosis, acute allogeneic transplant rejection, chronic allogeneic transplant nephropathy, diabetic nephropathy, glomerulonephropathy, cardiomyopathy, heart failure, myocardial ischemia, myocardial infarction, systemic sclerosis, thermal injury, burns, hypertrophic scars, keloids, gingivitis with fever, cirrhosis or tumors, bone regrowth, neurodegeneration, amyotrophic lateral sclerosis, stroke, transient ischemic attack, or uveitis.