Radiolabeled cannabinoid receptor 2 ligands

Abstract

The present invention relates to radiolabeled cannabinoid receptor 2 ligands. In particular, the present invention relates to compounds of formula (I), wherein R 1 , R 2 and R 3 are as defined in the description and in the claims. The compounds of formula (I) can be used as radiolabeled ligands.

Description

[0001] This application is a divisional application of the application having a PCT International filing date of 25 June 2019, a PCT International application number of PCT / EP2019 / 066799, a Chinese national application number of 201980026097.4, and an invention title of “Radiolabeled Cannabinoid Receptor 2 Ligands”.

[0002] The present invention relates to a radiolabeled cannabinoid receptor 2 ligand.

[0003] The present invention particularly relates to a compound of formula (I)

[0004]

[0005] wherein

[0006] R 1 and R 2 are both ethyl; and

[0007] R 3 is 3-fluoropropyl;

[0008] with the proviso that at least one of R 1 , R 2 and R 3 comprises at least one radionuclide;

[0009] or a pharmaceutically acceptable salt thereof.

[0010] Cannabinoid receptors are a class of cell membrane receptors belonging to the G protein-coupled receptor superfamily. Two known subtypes exist, designated cannabinoid receptor 1 (CB1) and cannabinoid receptor 2 (CB2). CB1 receptors have a wide range of expression. They are mainly expressed in the central nervous (i.e. amygdala cerebellum, hippocampus) system and in smaller amounts in the periphery. CB2, encoded by the CNR2 gene, is mainly expressed in the periphery on cells of the immune system, such as macrophages, B- 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 present in the brain, where they are mainly found on microglia rather than neurons (Cabral, G.A. et al. Br J Pharmacol 2008, 153(2), 240-51).

[0011] Interest in CB2 receptor agonists has steadily risen over the past decade (currently 30-40 patent applications / year) due to the fact that many 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 mass regulation (Bab, I. et al. Br J Pharmacol 2008, 153(2), 182-8), neurogenic inflammation (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) and liver 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).

[0012] Ischemia / reperfusion (I / R) injury is the major cause of tissue damage that occurs in conditions such as stroke, myocardial infarction, cardiopulmonary bypass and other vascular surgery and organ transplantation, and is the major mechanism that complicates the process of circulatory shock of multiple etiologies. All of these conditions are characterized by disruption of normal blood pressure supply, which leads to insufficient tissue oxygenation. Reoxygenation, e.g., reperfusion, is the ultimate treatment for restoring normal tissue oxygenation. However, the lack of oxygen and nutrients from the blood creates a condition in which the restoration of circulation leads to further tissue damage. The damage of reperfusion injury is in part due to an inflammatory response of the damaged tissue. White blood cells carried to the area by the newly returned blood release many inflammatory factors such as interleukins and free radicals in response to tissue damage. The restored blood flow re-introduces oxygen within the cells, which damages cellular proteins, DNA and plasma membranes.

[0013] Remote ischemic preconditioning (RIPC) represents a strategy to exploit the body's endogenous protective capabilities against injury due to ischemia and reperfusion. It describes a very interesting phenomenon in which a short, non-lethal ischemia and reperfusion of one organ or tissue provides resistance to a subsequent episode of "lethal" ischemia-reperfusion injury in a distant organ or tissue. Although multiple hypotheses have been proposed, the exact mechanism by which a short ischemia and reperfusion of an organ or tissue provides protection is currently unknown.

[0014] The humoral hypothesis proposes that endogenous substances produced in the remote organ or tissue (such as adenosine, bradykinin, opioids, CGRP, endocannabinoids, angiotensin I or some other substance of a yet unidentified humoral factor) enter the bloodstream and activate their respective receptors in the target tissue, thereby recruiting various intracellular pathways involved in myocardial protection in ischemic preconditioning.

[0015] Recent data suggest that endocannabinoids and their receptors, in particular CB2, can be involved in preconditioning and contribute to the prevention of reperfusion injury by down-regulating the inflammatory response (Pacher, P. et al. Br J Pharmacol 2008, 153(2), 252-62). In particular, recent studies with CB2 tool agonists have confirmed 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).

[0016] Furthermore, in the last few years, an increasing body of literature suggests that CB2 can also be of interest in sub-chronic and chronic settings. Specific up-regulation of CB1 and CB2 has been shown to be relevant to the associated expression of CB2 in myofibroblasts, cells responsible for the progression of fibrosis, 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).

[0017] Activation of CB2 receptors by selective CB2 agonists has indeed been shown to exert an anti-fibrotic effect in systemic sclerosis (Garcia-Gonzalez, E. et al. Rheumatology (Oxford) 2009, 48(9), 1050-6) and CB2 receptors have emerged as key targets in experimental skin fibrosis (Akhmetshina, A. et al. Arthritis Rheum 2009, 60(4), 1129-36) and in the pathophysiology of the liver, including fibrogenesis associated with chronic liver diseases (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).

[0018] The need to unambiguously detect CB2 in tissues has accompanied the growing interest in this receptor. The use of appropriate tools to assess CB2 expression and receptor occupancy in patients or samples can validate the targeted cells for expression, allow dose finding of any CB2 ligand in human studies, or for diagnostic purposes.

[0019] So far, efficient tools for detecting CB2 receptor protein in tissues are still lacking, as a consequence of the low expression level of CB2 receptors. Another reason for the lack of specific antibodies as detection tools for CB2 can stem from the apparent difficulty of using CB2 as an immunogen.

[0020] A number of PET tracers targeting CB2 receptors have been described in recent years (Caillie, F et al, Mol. Pharmaceutics, 2017, 14(11), 4064-4078 and references mentioned therein). All of them are labelled with short-lived radioisotopes 11 C (with a decay half-life of 20.3 min) or lack selectivity with respect to CB1 receptors and have a high lipophilicity, resulting in an unfavourable signal-to-noise ratio. A novel PET tracer with high selectivity and specificity for CB2 and containing 18 F tags would be highly desirable. In particular, a longer-lived 18 F isotope (with a decay half-life of 110 min) would greatly facilitate the distribution and use of the tracer after its production. In addition, 18 The low positron emission of F makes this isotope the preferred PET radionuclide for obtaining images with higher spatial resolution.

[0021] The incorporation of fluorine atoms into the chemical structure of small molecules has profound effects on their physico-chemical and biological properties (K. Mϋller et al., 2007, 317(5846), 1881-1886). Therefore, when looking for PET tracer candidate structures that are suitable for radiofluorination, it is not obvious to identify a suitable compound that maintains and combines all the desired properties in one molecule.

[0022] Surprisingly, compounds of formula (I) as defined above have been identified to have the desired properties and were found to have a highly reduced non-specific binding.

[0023] Compounds of formula (I) have been proven to specifically and selectively bind to membranes prepared from cells recombinantly expressing CB2 receptors. Furthermore, compounds of formula (I) have been proven to specifically label CB2 receptors in spleen tissue, which is an organ with high expression of both CB1 and CB2 receptors. Moreover, in spleen tissue isolated from CB2 receptor deficient mice, no binding by compounds of formula (I) occurred. In this particular case, the total binding signal could not be reduced by an excess of unlabeled (R 1 = CH3) compounds of formula (I).

[0024] Therefore, compounds of formula (I) can be used, for example, for tissue autoradiography and PET imaging, for example to assess receptor expression and receptor occupancy, for dose finding of any CB2 ligand in human studies or for diagnostic purposes.

[0025] In the present specification, the term "radionuclide" defines an isotope of an atom having an unstable nucleus and undergoing radioactive decay. Particular radionuclides of the present invention are [ 3 H], [ 18 F], [ 11 C] and [ 14 C], more particularly [ 3 H] and [ 18 F].

[0026] The term "binding constant" refers to the equilibrium constant associated with the binding reaction of a ligand-receptor.

[0027] The term "selective binding" characterizes the binding of a ligand to a very limited type of receptors.

[0028] Therefore, the present invention relates to:

[0029] a compound of formula (I), wherein A is CH;

[0030] a compound of formula (I), wherein R 1 and R 2 both comprise at least one radionuclide or R3 comprising a radionuclide;

[0031] A compound of formula (I), wherein at least one radionuclide is independently selected from the group consisting of [ 3 H], [ 18 F] and [ 11 C];

[0032] A compound of formula (I), wherein R 1 and R 2 are both -C 3 HH-C 3 HH2;

[0033] A compound of formula (I), wherein R 3 is -CH2-CH2-CH2 18 F or -CD2-CD2-CD2 18 F;

[0034] A compound of formula (I) selected from the group consisting of

[0035] 2-Ethyl-2-[[6-[[(1S,2S)-2-(hydroxymethyl)cyclopropyl]methoxy]-5-(3- methoxyazetidin-1-yl)pyridine-2-carbonyl]amino]butyric acid 3-[ 18 F] fluorine- propyl ester; and

[0036] 2-Ethyl-2-[[6-[[(1S,2S)-2-(hydroxymethyl)cyclopropyl]methoxy]-5-(3- methoxyazetidin-1-yl)pyridine-2-carbonyl]amino]butyric acid (1,1,2,2,3,3- hexadeuterio-3- 18 F] fluorine- propyl ester; and

[0037] 2-(1,2-Dideuterioethyl)-2-[[6-[[(1S,2S)-2-(hydroxymethyl)cyclopropyl]methoxy]-5-(3- methoxyazetidin-1-yl)pyridine-2-carbonyl]amino]-3,4-dideuterio-butyric acid 3- fluorine propyl ester;

[0038] or a pharmaceutically acceptable salt thereof;

[0039] Use of a compound of formula (I) for localizing CB2 receptors in a patient, animal or sample;

[0040] Use of a compound of formula (I) for imaging CB2 receptors in a patient, animal or sample;

[0041] Use of a compound of formula (I) for determining whether another compound binds to CB2 receptors;

[0042] The use of a compound of formula (I) for determining whether another compound binds to the CB2 receptor also includes measuring the binding constant of said other compound to said CB2 receptor;

[0043] The use of a compound of formula (I) for determining whether another compound binds to the CB2 receptor in vivo is by means of a receptor occupancy study using PET;

[0044] The use as defined above is carried out in the presence of CB1 receptors.

[0045] The use of a compound of formula (I) for determining whether a disease is characterized by a change in the expression of CB2 receptors;

[0046] Use of a compound of formula (I) for determining whether a disease is characterized by a change in the expression of CB2 receptors, wherein the disease is pain, atherosclerosis, age-related macular degeneration, diabetic retinopathy, glaucoma, diabetes mellitus, inflammation, inflammatory bowel disease, ischemia-reperfusion injury, acute liver failure, liver fibrosis, lung fibrosis, kidney fibrosis, systemic fibrosis, acute allograft rejection, chronic allograft nephropathy, diabetic nephropathy, glomerulonephropathy, cardiomyopathy, heart failure, myocardial ischemia / infarction, systemic sclerosis, thermal injury, burning, hypertrophic scars, keloids, gingivitis pyrexia, liver cirrhosis or tumors, regulation of bone mass, neurodegeneration, stroke, transient ischemic attack or uveitis;

[0047] A compound of formula (I) for use in diagnosing a disease in a patient or tissue;

[0048] A compound of formula (I) for use in diagnosing a disease in a patient or tissue as defined above, wherein the disease is characterized by a change in the expression of CB2 receptors in the patient or tissue compared to the expression of CB2 receptors in a healthy subject or tissue;

[0049] A compound for use as defined above, wherein the diagnosis comprises the step of comparing the expression of CB2 receptors in the patient or tissue to the expression of CB2 receptors in a healthy subject or tissue;

[0050] A compound of formula (I) for use in predicting whether a patient affected by a disease is likely to respond to a treatment involving the administration of a CB2 ligand;

[0051] A compound of formula (I) for use in predicting whether a patient affected by a disease is likely to respond to a treatment involving the administration of a CB2 ligand, comprising comparing the expression of CB2 receptors in the patient to the expression of CB2 receptors in a healthy subject or tissue;

[0052] A compound of formula (I) for use in assessing the efficacy of a medical treatment in a patient, comprising monitoring the CB2 receptor density (i.e. CB2 receptor expression) in the patient before, during and / or after the medical treatment; and

[0053] A compound of formula (I) for use in determining the dose of a CB2 ligand that needs to be administered to a patient in need thereof.

[0054] The present invention further relates to a method for identifying a compound that binds to CB2 receptors, comprising the steps of:

[0055] (a) contacting a compound suspected of binding to CB2 receptors with a sample comprising CB2 receptors and a compound of formula (I); and

[0056] (b) monitoring whether the compound suspected of binding to CB2 receptors affects the binding of the compound of formula (I) to CB2 receptors.

[0057] The present invention also relates to a method as defined above, further comprising the step of measuring the strength of the binding of CB2 receptors to the compound suspected of binding to CB2 receptors.

[0058] The present invention also relates to a method for identifying a cell receptor that is a CB2 receptor, comprising the steps of:

[0059] (a) contacting a sample suspected of comprising CB2 receptors with a compound of formula (I); and

[0060] (b) monitoring whether binding of the compound of formula (I) occurs; and

[0061] (c) optionally further contacting the sample with another known CB2 ligand and monitoring whether the known CB2 ligand has been displaced from its binding site by the compound of formula (I).

[0062] The present application also relates to a method for measuring the percentage of CB2 receptors occupied by a compound suspected of binding to CB2 receptors (when the compound is contacted with a sample) in a sample, comprising the steps of:

[0063] (a) contacting a sample comprising at least one CB2 receptor with a compound of formula (I) to determine a baseline signal;

[0064] (b) contacting the sample with a dose of the compound suspected of binding to CB2 receptors and the compound of formula (I);

[0065] (c) monitoring displacement of the compound of formula (I) by the compound suspected of binding to CB2 receptors; and

[0066] (d) calculating the percentage of CB2 receptors occupied by the compound suspected of binding to CB2 receptors.

[0067] The present application also relates to a method for measuring the percentage of CB2 receptors occupied by a compound suspected of binding to CB2 receptors (when a dose of the compound is administered to a vertebrate) in a living vertebrate (including a human subject), comprising the steps of:

[0068] (a) administering a compound of formula (I) to the vertebrate to determine a baseline signal;

[0069] (b) administering to the vertebrate simultaneously the dose of the compound suspected of binding to CB2 receptors and the compound of formula (I);

[0070] (c) monitoring displacement of the compound of formula (I) by the compound suspected of binding to CB2 receptors; and

[0071] (d) calculating the percentage of CB2 receptors occupied by the compound suspected of binding to CB2 receptors.

[0072] The present application also relates to a method for determining the dose of a CB2 ligand that needs to be administered to a vertebrate (including a human subject) in need thereof, comprising the steps of:

[0073] (a) administering a compound of formula (I) to the vertebrate and determining a baseline signal;

[0074] (b) administering to the vertebrate different doses of a CB2 ligand and simultaneously administering to the vertebrate the compound of formula (I);

[0075] (c) monitoring the displacement of the compound of formula (I) by different doses of CB2 ligands; and

[0076] (d) calculating the percentage of CB2 receptors occupied by the CB2 ligand and determining the dose / occupancy relationship.

[0077] In step (a) above, the baseline signal is taken as 100%.

[0078] The present application also relates to a method for determining whether a disease is characterized by a change in the expression of CB2 receptors, comprising the following steps:

[0079] (a) contacting a compound of formula (I) with a sample affected by the disease and a healthy sample, or administering to a subject affected by the disease and to a healthy subject;

[0080] (b) monitoring whether binding of the compound of formula (I) occurs in both samples; and

[0081] (c) comparing the amount of compound of formula (I) bound to CB2 receptors in both samples.

[0082] The imaging techniques mentioned above for these steps above include, but are not limited to, positron emission tomography (PET) or single photon emission computed tomography (SPECT), in particular PET.

[0083] The present application also relates to a method of the present application, wherein autoradiography is used during the monitoring.

[0084] The present application further relates to a pharmaceutical composition comprising a compound of formula (I).

[0085] The present application also relates to a compound of formula (I) for use as a diagnostic, i.e. for the diagnosis of a disease.

[0086] The present application also relates to a compound of formula (I) for use in the diagnosis of pain, atherosclerosis, age-related macular degeneration, diabetic retinopathy, glaucoma, diabetes, inflammation, inflammatory bowel disease, ischemia-reperfusion injury, acute liver failure, liver fibrosis, lung fibrosis, kidney fibrosis, systemic fibrosis, acute allograft rejection, chronic allograft nephropathy, diabetic nephropathy, glomerulonephropathy, cardiomyopathy, heart failure, myocardial ischemia, myocardial infarction, systemic sclerosis, thermal injury, burn injury, hypertrophic scarring, keloid scarring, gingivitis pyrexia, cirrhosis or tumors, bone mass regulation, neurodegeneration, stroke, transient ischemic attack or uveitis.

[0087] The synthesis of the compound of formula (I) can be achieved, for example, according to the following scheme.

[0088] Scheme 1

[0089]

[0090] For the target compound 2-ethyl-2-[[6-[[(1S,2S)-2-(hydroxymethyl)cyclopropyl]methoxy]-5-(3-methoxyazacyclobut-1-yl)pyridine-2-carbonyl]amino]butyric acid 3-[ 18 F]fluoryl propyl ester (Ia) and 2-ethyl-2-[[6-[[(1S,2S)-2-(hydroxymethyl)cyclopropyl]methoxy]-5-(3-methoxyazacyclobut-1-yl)pyridine-2-carbonyl]amino]butyric acid (1,1,2,2,3,3-hexadeuterated-3-[ 18 The carboxylic acid precursor 16 of the fluoryl-propyl ester (Ib) can be generated as described in Scheme 1 from commercially available succinic anhydride 1, 1-menthol 2 and 5-bromo-6-chloropyridin-2-carboxylic acid 9 or by applying another synthetic strategy known to those skilled in the art.

[0091] Option 2

[0092]

[0093] As described in Scheme 2, the target compound (Ia) is obtained via a two-step procedure starting with carboxylic acid 16 and bis(toluenesulfonate) 17. In the second step, [Ia is obtained by using acetonitrile in...] 18 The nucleophilic substitution of F]KF / Kryptofix 2.2.2 without carrier addition, or other methods known to those skilled in the art, can introduce [the substance] with highly specific activity. 18 F.

[0094] Option 3

[0095]

[0096] As described in Scheme 3, starting with carboxylic acid 16 and hexadeuterated bis-p-benzenesulfonate 19, the deuterated target compound (Ib) can be obtained similarly to its non-deuterated analogue (Ia) via a two-step procedure. In the second step, via the use of […] in acetonitrile 18 The nucleophilic substitution of F]KF / Kryptofix 2.2.2 without carrier addition, or other methods known to those skilled in the art, can introduce [the substance] with highly specific activity. 18 F.

[0097] Option 4

[0098]

[0099] The tritium labeled target compound (Ic) can be synthesized from carboxylic acid 16 and amine 24 following the procedure described in Scheme 4 or any other route known to the skilled person. In the radiolabeling step, bis-olefin 25 is subjected to a reduction with tritium gas to provide 2-(1,2-ditrifluoroethyl)-2-[[6-[[(1 S,2S)-2-(hydroxymethyl)cyclopropyl]methoxy]-5-(3-methoxyazetidin-1 -yl)pyridine-2-carbonyl]amino]-3,4-ditrifluoro-butanoic acid 3-fluoropropyl ester.

[0100] The present application therefore also relates to a process for preparing a compound of formula (I), said process comprising one of the following steps:

[0101] (a) reacting a compound of formula (A)

[0102]

[0103] with a nucleophilic [ 18 F] fluoride reagent; or

[0104] (b) reacting a compound of formula (B)

[0105]

[0106] with [ 3 H]2;

[0107] wherein LG is a leaving group and wherein R 1 to R 3 are as defined above.

[0108] The leaving group is for example p-toluenesulfonyloxy, 4-nitrobenzenesulfonyloxy, methanesulfonyloxy or trifluoromethanesulfonyloxy.

[0109] In step (a), the [ 18 F] fluoride reagent can for example be [ 18 F] KF / K 2.2.2 .

[0110] Step (a) can for example be carried out in acetonitrile.

[0111] Step (a) can be carried out at a temperature between 25 and 200°C, but heating is not necessary.

[0112] The present application further relates to a compound prepared according to the process of the present application.

[0113] The present application will now be illustrated by non-limiting examples. Examples

[0114] Abbreviations

[0115] rac-BINAP = racemic 2,2'-bis(diphenylphosphino)-1,1 '-binaphthyl); CAN = Chemical Abstracts Service Number; DCM = dichloromethane; DIPEA = N-ethyl-N- isopropylpropan-2-amine; DMF = dimethylformamide; DPPA = diphenyl phosphoryl azide; EI = electron impact; EtOAc = ethyl acetate; HATU = 1 -[bis(dimethylamino)methylene]-1 H-1,2,3-triazolo[4,5-b]pyridinium 3-oxide hexafluorophosphate; LAH = lithium aluminium hydride; LC = liquid chromatography; LiTMP = lithium 2,2,6,6-tetramethylpiperidide; MS = mass spectrometry; NMR = nuclear magnetic resonance; NMR data are reported in parts per million (δ) relative to the internal reference tetramethylsilane, and referenced to the deuterium lock field signal from the sample solvent (d6-DMSO, unless otherwise stated); coupling constants (J) are in Hertz (Hz); PTSA = p-toluenesulfonic acid; Rt = retention time; SOR = specific optical rotation; TBTU = O-(benzotriazol-1 -yl)-N,N,N',N'-tetramethyl-uronium tetrafluoroborate; THF = tetrahydrofuran.

[0116] Experiments

[0117] All reactions were performed in flame dried glassware. Analytical reagents were used to perform the reactions and dry solvents were used where required without further purification. Unless otherwise stated, reagents were purchased from reputable commercial suppliers and used without further purification. All 1 H NMR spectra were recorded on a Bruker Advance Ultra Shield 300 MHz spectrometer. Chemical shifts reported are relative to the deuterated solvent. Mass spectra were recorded on a PE Sciex API 150 EX LC / MS turbo spray system. Flash chromatography was performed using an Isco Combi Flash companion with different size pre-packed silica cartridges (230-400 mesh, 40-63 μm) from multiple commercial suppliers. Thin layer chromatography was performed on pre-coated plates (20 x 20 cm, silica gel F254) purchased from Merck KgaA and visualized using a 254 nm CAMAG UV lamp or using basic potassium permanganate solution. All reactions were monitored using thin layer chromatography, LCMS and 1 H NMR spectra were recorded on a Bruker Advance Ultra Shield 300 MHz spectrometer. Chemical shifts reported are relative to the deuterated solvent. Mass spectra were recorded on a PE Sciex API 150 EX LC / MS turbo spray system. Flash chromatography was performed using an Isco Combi Flash companion with different size pre-packed silica cartridges (230-400 mesh, 40-63 μm) from multiple commercial suppliers. Thin layer chromatography was performed on pre-coated plates (20 x 20 cm, silica gel F254) purchased from Merck KgaA and visualized using a 254 nm CAMAG UV lamp or using basic potassium permanganate solution. All reactions were monitored using thin layer chromatography, LCMS and

[0118] Example 1

[0119] 2-ethyl-2-[[6-[[(1S,2S)-2-(hydroxymethyl)cyclopropyl]methoxy]-5-(3- methoxyazetidin-1-yl)pyridine-2-carbonyl]amino]butanoic acid 3-18 F]Fluoropropyl ester

[0120]

[0121] a) Bis(1R,2S,5R)-5-methyl-2-(propyl-2-yl)cyclohexyl succinate

[0122]

[0123] A 2L single-necked round-bottom flask was equipped with a stirrer, a Dean-Stark separator, and a condenser. Succinic anhydride (64 g, 0.64 mol, 1 eq.), L-menthol (200 g, 1.3 mol, 2 eq.), p-toluenesulfonic acid monohydrate (1.1 g, 6.39 mmol, 0.01 eq.), and toluene (576 mL) were added to the flask. The mixture was heated under reflux for 24 h, cooled to 25 °C, diluted with hexane (640 mL), and poured into a mixture of saturated sodium bicarbonate aqueous solution (800 mL), methanol (320 mL), and water (320 mL). The layers were separated, and the aqueous phase was extracted with hexane (2 x 320 mL). The organic phases were combined, washed with brine (640 mL), dried over sodium sulfate, and filtered. The solvent was removed under reduced pressure, and the crude product was dissolved in methanol (240 mL). The solution was cooled to +4°C and held for 16 hours to form colorless crystals, which were collected by vacuum filtration. The crystals were purified by recrystallization from methanol (240 mL) to give pure bis(1R,2S,5R)-5-methyl-2-(propyl-2-yl)cyclohexyl succinate (212 g, 84%).

[0124] SOR value: [-87.64°], in Below, a 1.0132% solution in CHCl3.

[0125] b)(1S,2S)-cyclopropane-1,2-dicarboxylic acid 1,2-bis(1R,2S,5R)-5-methyl-2-(propyl-2-yl)cyclohexyl ester

[0126]

[0127] Butyllithium 1.8 M in THF (152.2 mmol, 84 mL) was added to 225 mL of THF at 0°C under N2atmosphere. Lithium tetramethylpiperidine (28.2 mL, 167 mmol) was added dropwise over a period of 20 min with stirring. Stirring was continued at 0°C for 1 h. The mixture was then cooled to -78°C. A solution of succinic acid bis(1R,2S,5R)-5-methyl-2-(propan-2-yl)cyclohexyl ester (30 g, 76.1 mmol) in THF (60 mL) was added dropwise over a period of 20 min. The yellow solution was stirred for 1 h. Bromochloromethane (4.08 mL, 60.91 mmol) was added dropwise over a period of 20 min. The mixture was stirred at -78°C for 3 h. A saturated aqueous solution of NH4CI (120 mL) was added. After stirring at 25°C for 30 min, the mixture was extracted with EtOAc (3 x 150 mL). The combined organic layers were washed with brine (200 mL), dried over Na2S04, filtered, and concentrated in vacuo. The crude product was purified by column chromatography (Si02, 100-200 mesh, 0.5-1% ethyl acetate in hexanes) to give the title compound (38 g, 42%) as colorless crystals. This material was recrystallized from methanol (380 mL) to give pure (1S,2S)-cyclopropane-1,2-dicarboxylic acid 1,2-bis(1R,2S,5R)-5-methyl-2-(propan-2-yl)cyclohexyl ester (27 g, 36%).

[0128] SOR value: [ + 18.18°] in CHCI3. 1.0288% solution in CHCI3.

[0129] c) (1S,2S)-Cyclopropane-1,2-dicarboxylic acid mono-((1R,2S,5R)-2-isopropyl-5- methyl-cyclohexyl) ester

[0130]

[0131] To a stirred solution of (1S,2S)-cyclopropane-1,2-dicarboxylic acid 1,2-bis(1R,2S,5R)- 5-methyl-2-(propan-2-yl)cyclohexyl ester (25 g, 61.58 mmol) in isopropanol (250 mL) was added a 5M solution of NaOH (13.54 mL, 67.73 mmol) at 25 °C. The mixture was stirred at 70 °C for 16 h. The organic solvent was removed under reduced pressure. Water (200 mL) was added and the mixture was washed with diethyl ether (2 x 150 mL). The aqueous layer was acidified with 2N HC1 (pH ~ 2) and extracted with ethyl acetate (3 x 250 mL). The combined organic layers were dried over Na2S04, filtered and concentrated under reduced pressure to give (1S,2S)-2-({[(1R,2S,5R)-5-methyl-2-(propan-2-yl)cyclohexyl]oxy}carbonyl)cyclopropane-1- carboxylic acid (11.4 g, 69%) as off-white semi-solid.

[0132] d) (1S,2S)-2-(Hydroxymethyl)cyclopropane-1-carboxylic acid (1R,2S,5R)-5-methyl-2- (propan-2-yl)cyclohexyl ester

[0133]

[0134] To a stirred solution of (1S,2S)-cyclopropane-1,2-dicarboxylic acid mono-((1R,2S,5R)-2- isopropyl-5-methyl-cyclohexyl) ester (20 g, 74.63 mmol) in THF (200 mL) was added 1M solution of borane in THF (56 mL) drop wise at -78 °C. The mixture was stirred at 25 °C for 1 h and quenched with aqueous NH4C1 (150 mL). The organic solvent was removed under reduced pressure. Water (50 mL) was added and the mixture was extracted with ethyl acetate (2 x 100 mL). The combined organic layers were washed with brine (80 mL), dried over Na2S04, filtered and concentrated under reduced pressure. The crude was purified by silica gel column chromatography (15-19% ethyl acetate / hexane) to give (1S,2S)-2-(hydroxymethyl)cyclopropane-1-carboxylic acid (1R,2S,5R)-5-methyl-2- (propan-2-yl)cyclohexyl ester (13.7 g, 72%) as yellowish semi-solid.

[0135] e) (1S,2S)-2-[(Benzyl oxy)methyl]cyclopropane-1-carboxylic acid (1R,2S,5R)-5-methyl-2- (propan-2-yl)cyclohexyl ester

[0136]

[0137] To a stirred solution of (1S,2S)-2-(hydroxymethyl)cyclopropane-1 -carboxylic acid (1R,2S,5R)-5-methyl-2-(propan-2-yl)cyclohexyl ester (20 g, 78.74 mmol) in DMF (140 mL) was added NaH (4.72 g, 118.11 mmol) at 0 °C. The mixture was stirred at 25 °C for 30 min. Benzyl bromide (18.7 mL, 157.5 mmol) was added and stirring was continued at 25 °C for 30 min. Aqueous NH4CI (150 mL) was added and the mixture was extracted with EtOAc (2 x 150 mL). The combined organic layers were washed with water (3 x 120 mL), dried over Na2S04, filtered and concentrated under reduced pressure. The crude was purified by silica gel column chromatography (1.9% EtOAc / hexane) to afford (1S,2S)-2-[(benyloxy)methyl]cyclopropane-1 -carboxylic acid (1R,2S,5R)-5-methyl-2-(propan-2-yl)cyclohexyl ester (22 g, 8%) as a light yellow oil.

[0138] f) [(1S,2S)-2-[(benyloxy)methyl]cyclopropyl]methanol

[0139]

[0140] To a stirred solution of (1S,2S)-2-[(benyloxy)methyl]cyclopropane-1 -carboxylic acid (1R,2S,5R)-5-methyl-2-(propan-2-yl)cyclohexyl ester (10 g, 29.01 mmol) in THF (200 mL) was added LAH (58.1 mL, 1 M in THF) at 0 °C. The reaction mixture was stirred at 0 °C for 40 min and quenched with aqueous NH4CI (100 mL). The organic solvent was removed under reduced pressure. The solution was extracted with ethyl acetate (3 x 100 mL). The combined organic layers were taken to dryness and the crude was purified using silica gel column chromatography (30-35% ethyl acetate / hexane) to afford [(1S,2S)-2-[(benyloxy)methyl]cyclopropyl]methanol (5.33 g, 95%) as a light yellow oil.

[0141] g) 6-{[(1S,2S)-2-[(benyloxy)methyl]cyclopropyl]methoxy}-5-bromopyridine-2- carboxylic acid

[0142]

[0143] To a solution of 5-bromo-6-chloropyridine-2-carboxylic acid (CAN 959958-25-9, 4 g, 19.80 mmol) in DMF (45 mL) was added NaH (2.77 g, 69.31 mmol) portion wise at 0 °C and stirred at 0 °C for 20 min. [(1S,2S)-2-[(benzyloxy)methyl]cyclopropyl]methanol (4.18 g, 21.78 mmol) in DMF (15 mL) was added drop wise at 0 °C. The mixture was stirred at 25 °C for 15 min, heated to 80 °C for 3 h, cooled to 25 °C and quenched with 2N aqueous HC1 to pH ~ 2. Water (100 mL) was added and the mixture was extracted with EtOAc (3 x 150 mL). The combined organic layers were washed with water (4 x 50 mL) and brine (50 mL), dried over Na2S04and concentrated under reduced pressure to give 6-{[(1S,2S)-2-[(benzyloxy)methyl]cyclopropyl]methoxy}-5-bromopyridine-2-carboxylic acid (7.7 g, 99%) as off-white viscous liquid.

[0144] LCMS: Column Zorbax Ext C 18 (50 X 4.6 mm), 5μ, (mobile phase: in 1.5 min, from 90% [10 mM NH4OAc in water] and 10% [CH3CN] to 70% [10 mM NH4OAc in water] and 30% [CH3CN], further in 3.0 min, to 10% [10 mM NH4OAc in water] and 90% [CH3CN], keep this mobile phase composition until 4 min and finally in 5 min back to initial conditions). Purity 76.8%, Rt = 2.60 min, MS expected: 391, MS found: 391.8 ([M+H]). +

[0145] h) 2-[(6-{[(1S,2S)-2-[(benzyloxy)methyl]cyclopropyl]methoxy}-5-bromo-pyridin-2-yl)formamidyl]-2- ethylbutanoic acid ethyl ester

[0146]

[0147] ​To a solution of 6-{[(1S,2S)-2-[(benzyloxy)methyl]cyclopropyl]methoxy}-5- bromonicotinic acid (15.5 g, 39.54 mmol) in DMF (100 mL), was added DIPEA (27.49 mL, 158.16 mmol), ethyl 2-amino-2-ethylbutanoate (CAN 189631-96-7, 7.73 g, 39.54 mmol) and TBTU (15.25 g, 47.449 mmol). The reaction mixture was stirred at 25 °C for 16 h, poured into water (170 mL) and extracted with EtOAc (3 x 200 mL). The combined organic layers were washed with water (4 x 120 mL) and brine (100 mL), dried over Na2S04, filtered and taken to dryness. The crude was purified via silica gel column chromatography (25% ethyl acetate / hexane) to afford ethyl 2-[(6-{[(1S,2S)-2-[(benzyloxy)methyl]cyclopropyl]methoxy}-5- bromopyridin-2-yl)formamido]-2-ethylbutanoate (20.5 g, 97%) as a light brown oil.

[0148] LCMS: Column Zorbax Ext C 18 (50 X 4.6 mm), 5μ, (mobile phase: in 1.5 min, from 90% [10 mM NH4OAc in water] and 10% [CH3CN] to 70% [10 mM NH4OAc in water] and 30% [CH3CN], further in 3.0 min, to 10% [10 mM NH4OAc in water] and 90% [CH3CN], keep this mobile phase composition until 4 min and finally in 5 min back to initial conditions). Purity 91.47%, Rt = 2.58 min, MS expected: 533, MS found: 533.0 [(M+H] + ).

[0149] i) Ethyl 2-[(6-{[(1S,2S)-2-[(benzyloxy)methyl]cyclopropyl]methoxy}-5-(3- methoxyazetidin-1-yl)pyridin-2-yl)formamido]-2-ethylbutanoate

[0150]

[0151] To a solution of ethyl 2-[(6-{[(1S,2S)-2-[(benzyloxy)methyl]cyclopropyl]methoxy}-5- bromopyridin-2-yl)formamidyl]-2-ethylbutanoate (4.0 g, 7.5 mmol) in toluene (160 mL) was added 3-methoxyazetidine (1.39 g, 11.3 mmol) and cesium carbonate (7.33 g, 22.5 mmol). The mixture was degassed with argon for 10 min. Rac-BINAP (0.935 g, 1.50 mmol) and Pd(II) acetate (0.34 g, 1.50 mmol) were added. The mixture was heated to 110 °C for 3 h, diluted with EtOAc (100 mL), filtered over a bed of celite and washed with EtOAc (3 x 100 mL). The filtrate was concentrated and the crude purified by column chromatography on silica gel (42-50% ethyl acetate / hexane) to give ethyl 2-[(6-{[(1S,2S)-2-[(benzyloxy)methyl]cyclopropyl]methoxy}-5-(3- methoxyazetidin-1-yl)pyridin-2-yl)formamidyl]-2-ethylbutanoate (3.1 g, 76%) as a light brown oil.

[0152] LCMS: Column Zorbax Ext C 18 (50 X 4.6 mm), 5μ, (mobile phase: in 1.5 min from 90% [10 mM NH4OAc in water] and 10% [CH3CN] to 70% [10 mM NH4OAc in water] and 30% [CH3CN], further in 3.0 min to 10% [10 mM NH4OAc in water] and 90% [CH3CN], keep this mobile phase composition until 4 min and finally in 5 min back to initial conditions). Purity 96.7%, Rt = 2.37 min, MS expected: 539, MS found: 539.9 ([M+H]). +

[0153] j) Ethyl 2-ethyl-2-[(6-{[(1S,2S)-2-(hydroxymethyl)cyclopropyl]methoxy}-5-(3- methoxyazetidin-1-yl)pyridin-2-yl)formamidyl]butanoate

[0154]

[0155] ​A stirred solution of ethyl 2-[(6-{[(1S,2S)-2-[(benzyloxy)methyl]cyclopropyl]- methoxy}-5-(3-methoxyazetidin-1-yl)pyridin-2-yl)formamidyl]-2-ethylbutanoate (26 g, 48.24 mmol) in 735 mL EtOAc:MeOH (10:1) was degassed for 30 min. Pd / C (10%) (6.5 g) was added. The mixture was hydrogenated at 25 °C under 40 PSI of hydrogen atmosphere for 28 h, filtered through a bed of celite and washed with 10% MeOH / EtOAc (4 x 200 mL). The filtrate was evaporated under reduced pressure to give the crude product. The crude product was purified by silica gel column chromatography (10-50% EtOAc:hexane) to give ethyl 2-ethyl-2-[(6-{[(1S,2S)-2-(hydroxymethyl)cyclopropyl]methoxy}-5-(3- methoxyazetidin-1-yl)pyridin-2-yl)formamidyl]butanoate (19.3 g, 89%) as a colorless viscous liquid.

[0156] SOR value: [+15.51 °] in MeOH at 0.2514%.

[0157] LCMS: Column Zorbax Ext C 18 (50 X 4.6 mm), 5μ, (mobile phase: in 1.5 min, from 90% [10 mM NH4OAc in water] and 10% [CH3CN] to 70% [10 mM NH4OAc in water] and 30% [CH3CN], further in 3.0 min, to 10% [10 mM NH4OAc in water] and 90% [CH3CN], keep this mobile phase composition until 4 min and finally in 5 min back to initial conditions). Purity 98.9%, Rt = 3.26 min, MS expected: 449, MS found: 449.9 ([M+H]). +

[0158] k) 2-ethyl-2-[(6-{[(1S,2S)-2-(hydroxymethyl)cyclopropyl]methoxy}-5-(3- methoxyazetidin-1-yl)pyridin-2-yl)formamidyl]butanoic acid

[0159]

[0160] ​​In a 25 ml round bottom flask, 2-ethyl-2-[(6-{[(1S,2S)-2-(hydroxymethyl)cyclopropyl]methoxy}-5-(3-methoxyazetidin-1-yl)pyridin-2-yl)formamido]butanoic acid ethyl ester (100 mg, 0.22 mmol) was combined with THF (2.0 mL), MeOH (2.2 mL) and water (2.0 mL) to give a light yellow solution. KOH pellets (62 mg, 1.11 mmol) were added. The mixture was heated to 90 °C. After 18 h, the organic solvents were removed under reduced pressure. The aqueous phase was diluted with water (20 mL) and extracted with diethyl ether (2 x 10 mL). The combined organic layers were discarded. The aqueous phase was adjusted to pH ~ 2 (1 M HC1) and extracted with EtOAc (3 x 15 mL). The combined organic layers were washed with brine (10 mL), dried, filtered and taken to dryness under reduced pressure to give pure 2-ethyl-2-[(6-{[(1S,2S)-2-(hydroxymethyl)cyclopropyl]methoxy}-5-(3-methoxyazetidin-1-yl)pyridin-2-yl)formamido]butanoic acid (90 mg, 96%) as a colorless sticky material.

[0161] LCMS: Column Zorbax Ext C 18 (50 X 4.6 mm), 5μ, (mobile phase: in 1.5 min from 90% [10 mM NH4OAc in water] and 10% [CH3CN] to 70% [10 mM NH4OAc in water] and 30% [CH3CN], further in 3.0 min to 10% [10 mM NH4OAc in water] and 90% [CH3CN], keep this mobile phase composition until 4 min and finally in 5 min back to initial conditions). Purity 95.5%, Rt = 2.00 min, MS expected: 419, MS found: 420.4 ([M+H] + ).

[0162] l) 2-ethyl-2-[(6-{[(1S,2S)-2-(hydroxymethyl)cyclopropyl]methoxy}-5-(3-methoxyazetidin-1-yl)pyridin-2-yl)formamido]butanoic acid 3-{[(4-methylbenzene)sulfonyl]oxy}propyl ester

[0163]

[0164] To a solution of 2-ethyl-2-[(6-{[(1 S,2S)-2-(hydroxymethyl)cyclopropyl]methoxy}-5-(3- methoxyazetidin-1-yl)pyridin-2-yl)formamido]butanoic acid (260 mg, 0.62 mmol) in DMF (5 mL), K2CO3(256 mg, 1.85 mmol) and 4-methylbenzene-1 -sulfonic acid 3-{[(4- methylbenzene)sulfonyl]oxy}propyl ester (711 mg, 1.85 mmol) were added. The reaction mixture was stirred at 25 °C for 16 h, poured into water, quenched with 1 (N) aqueous HC1 and extracted with EtOAc (3 x 40 mL). The combined organic layers were washed with brine (30 mL), dried, filtered and concentrated in vacuo to give the crude product which was purified by combiflash using a silica column and 20-80% EtOAc in hexane to give pure 2-ethyl-2-[(6-{[(1 S,2S)-2-(hydroxymethyl)cyclopropyl]methoxy}-5-(3- methoxyazetidin-1-yl)pyridin-2-yl)formamido]butanoic acid 3-{[(4-methylbenzene)sulfonyl]oxy}propyl ester (255 mg, 65%) as a colorless viscous material.

[0165] LCMS: Column Zorbax Ext C 18 (50 X 4.6 mm), 5μ, (mobile phase: in 1.5 min, from 90% [10 mM NH4OAc in water] and 10% [CH3CN] to 70% [10 mM NH4OAc in water] and 30% [CH3CN], further in 3.0 min, to 10% [10 mM NH4OAc in water] and 90% [CH3CN], keep this mobile phase composition until 4 min and finally in 5 min back to initial conditions). Purity 90.7%, Rt = 3.48 min, MS expected: 633, MS found: 634.4 ([M+H] + ).

[0166] m) 2-ethyl-2-[[6-[[(1 S,2S)-2-(hydroxymethyl)cyclopropyl]methoxy]-5-(3- methoxyazetidin-1-yl)pyridine-2-carbonyl]amino]butanoic acid 3- 18 F] fluoropropyl ester

[0167] In a cyclotron 18 / 9 cyclotron (18-MeV; IBA Belgium), via e 18 O(p,n) 18 F nuclear reaction, from 98% enriched 18 O-water bombardment[ 18F] Fluoride ions, captured on an anion exchange cartridge (Waters SepPak Accell QMA cartridge), followed by K2CO3 (1 mg / mL) and Krypofix 222A solution of 2-ethyl-2-[(6-{[(1S,2S)-2-(hydroxymethyl)cyclopropyl]methoxy}-5-(3- methoxyazetidin-1-yl)pyridin-2-yl)formamidol]butanoic acid 3-{[(4-methylbenzene)sulfonyl]oxy}propyl ester (1 mg in 0.5 mL MeCN) was prepared in water / MeCN 1 :3 (2.5 mg / mL). Volatiles were removed at 110 °C under reduced pressure and with a gentle stream of nitrogen. Azeotropic drying was performed using MeCN (3 x 1 mL). After addition of 2-ethyl-2-[(6-{[(1S,2S)-2-(hydroxymethyl)cyclopropyl]methoxy}-5-(3- methoxyazetidin-1-yl)pyridin-2-yl)formamidol]butanoic acid 3-{[(4-methylbenzene)sulfonyl]oxy}propyl ester (1 mg in 0.5 mL MeCN), the reaction mixture was stirred at 90 °C for 10 min. The reaction mixture was then diluted with water (2.5 mL) and the crude purified by semi-preparative HPLC (Merck-Hitachi L2130 system) equipped with a radiation detector VRM 202 (Comecer, Netherlands) in combination with an ACE 5 C-18-300 (250 x 10.0 mm, 5 μm) column and a gradient solvent system: 0.1% H3PO4 in H2O (solvent A), MeCN (solvent B); 0.0-8.0 min, 20% B; 8.1-30.0 min, 20-90% B; 30.1-35.0 min, 90% B; 35.1-37.0 min, 90-20% B; 37.1-43.0 min, 20% B. The flow rate used was 4 mL / min and UV signal detection was performed at 230 nm. Product fractions from semi-preparative HPLC were collected in 35 mL of water and passed through a C18 cartridge (Waters, pre-conditioned with 5 mL EtOH and 5 mL water). The cartridge was washed with water (5 mL) and the title compound was then eluted using 0.5 mL EtOH. The radioligand 2-ethyl-2-[[6-[[(1S,2S)-2-(hydroxymethyl)cyclopropyl]methoxy]-5-(3- methoxyazetidin-1-yl)pyridine-2-carbonyl]amino]butanoic acid 3-(18F)fluorophenylpropyl ester was formulated in 5% EtOH in water for injection (WFI). 2-ethyl-2-[[6-[[(1S,2S)-2-(hydroxymethyl)cyclopropyl]methoxy]-5-(3- methoxyazetidin-1-yl)pyridine-2-carbonyl]amino]butanoic acid 3-(18F)fluorophenylpropyl ester was obtained with a molar activity in the range of 52-65 GBq / μmol and excellent radiochemical purity (>99%). The decay-corrected radiochemical yield was 9.0 ± 0.4%. Analytical quality control to determine radiochemical and chemical purity, specific activity and chemical identity was performed on an Agilent 1100 series HPLC system equipped with a UV detector and a GabiStar radio detector (Raytest).Separation conditions: 0.1% TFA in H20 (solvent A), MeCN (solvent B); 0.0-2.0 min, 20% B; 2.1-12.0 min, 20-90% B; 12.1-14.0 min, 90% B; 14.1-15.0 min, 90-20% B; 15.1-20.0 min, 20% B. The flow rate used was 1 mL / min and the UV signal was recorded at 230 nm. Molar activity was calculated by comparing the UV intensity of the formulated product to a calibration curve of the corresponding non-radioactive standard.

[0168] Example 2

[0169] 2-ethyl-2-[[6-[[(1S,2S)-2-(hydroxymethyl)cyclopropyl]methoxy]-5-(3- methoxyazetidin-1-yl)pyridine-2-carbonyl]amino]butanoic acid (1,1,2,2,3,3- hexadeuterio-3- 18 F]fluoran-yl-propyl) ester

[0170]

[0171] a) 4-methylbenzenesulfonic acid [1,1,2,2,3,3-hexadeuterio-3-(p- toluenesulfonyloxy)propyl] ester

[0172]

[0173] To a solution of 1,1,2,2,3,3-hexadeuteriopropane-1,3-diol (73 mg, 0.87 mmol) in DCM (1 mL) was added 2,6-dimethylpyridine (0.5 mL, 4.34 mmol) and tosyl chloride (496 mg, 2.60 mmol, 3 eq.). The reaction mixture was stirred at 25 °C for 17 h, diluted with DCM (20 mL), washed with 1 N aqueous HC1 (10 mL), dried, filtered and concentrated in vacuo. The crude product was purified by column chromatography on silica gel (5-30% EtOAc in hexanes) to give the title compound (205 mg, 61%) as a white solid.

[0174] LCMS: Column Zorbax Ext C 18 (50 X 4.6 mm), 5μ, (mobile phase: in 1.5 min, from 90% [10 mM NH4OAc in water] and 10% [CH3CN] to 70% [10 mM NH4OAc in water] and 30% [CH3CN], further in 3.0 min, to 10% [10 mM NH4OAc in water] and 90% [CH3CN], maintain this mobile phase composition up to 4 min and finally in 5 min back to initial conditions). Purity 99.84%, Rt = 3.48 min, MS theoretical value: 390, MS experimental value: 408.1 ([M+NH4] + ).

[0175] b) 2-ethyl-2-[[6-[[(1S,2S)-2-(hydroxymethyl)cyclopropyl]methoxy]-5-(3- methoxyazetidin-1-yl)pyridine-2-carbonyl]amino]butyric acid [1,1,2,2,3,3- hexadeutero-3-(p-toluenesulfonyloxy)propyl] ester

[0176]

[0177] To a solution of 2-ethyl-2-[(6-{[(1S,2S)-2-(hydroxymethyl)cyclopropyl]methoxy}-5- (3-methoxyazetidin-1-yl)pyridin-2-yl)formamidyl]butyric acid (Example 1k, 50 mg, 0.12 mmol) in DMF (5.0 mL), was added K2CO3 (49 mg, 0.35 mmol) and 4- methylbenzenesulfonic acid [1,1,2,2,3,3-hexadeutero-3-(p- toluenesulfonyloxy)propyl] ester (93 mg, 0.24 mmol). The reaction mixture was stirred for 17 h, quenched with water (30 mL) and extracted with EtOAc (3 x 20 mL). The combined organic layers were washed with brine (20 mL), dried, filtered and concentrated in vacuo. The crude was purified by column chromatography on silica gel (30-80% EtOAc in hexanes) to give the title compound (50 mg, 67%) as a colorless liquid.

[0178] LCMS: Zorbax Ext C 18 column (50 x 4.6 mm), 5 μm, (mobile phase: from 90% [10 mM NH4OAc aqueous solution] and 10% [CH3CN] to 70% [10 mM NH4OAc aqueous solution] and 30% [CH3CN] over 1.5 min, further to 10% [10 mM NH4OAc aqueous solution] and 90% [CH3CN] over 3.0 min, maintaining this mobile phase composition for 4 min and finally returning to initial conditions over 5 min). Purity: 95.5%, Rt = 3.47 min, MS theoretical value: 639, MS experimental value: 640.3 ([M+H)). + ).

[0179] c) 2-Ethyl-2-[[6-[[(1S,2S)-2-(hydroxymethyl)cyclopropyl]methoxy]-5-(3-methoxyazacyclobut-1-yl)pyridine-2-carbonyl]amino]butyric acid (1,1,2,2,3,3-hexadeuterated-3-[ 18 [F]fluoryl-propyl ester

[0180] In the Cyclone 18 / 9 cyclotron (18-MeV; IBA Belgium), via e 18 O(p,n) 18 F nuclear reaction, from 98% enrichment 18 Obtained by bombardment of O-water [ 18 F] fluoride ions. 18 F] Fluoride was trapped on an anion exchange cartridge (Waters SepPak Accell QMA cartridge carbonate), followed by K2CO3 (1 mg / mL) and Krypofix. 222A solution of 2-ethyl-2-[[6-[[(1S,2S)-2-(hydroxymethyl)cyclopropyl]methoxy]-5-(3- methoxyazetidin-1-yl)pyridine-2-carbonyl]amino]butyric acid [1,1,2,2,3,3-hexadeutero-3- (p-toluenesulfonyloxy)propyl] ester (1 mg in 0.5 mL MeCN) was added and the reaction mixture was stirred at 90 °C for 10 min. Subsequently the reaction mixture was diluted with water (2.5 mL) and the crude was purified by semi-preparative HPLC (Merck-Hitachi L2130 system) equipped with a radiation detector VRM 202 (Comecer, Netherlands) in combination with an ACE 5 C-18-300 (250 x 10.0 mm, 5 μm) column and a gradient solvent system: 0.1% H3PO4 in H2O (solvent A), MeCN (solvent B); 0.0-8.0 min, 20% B; 8.1-30.0 min, 20-90% B; 30.1-35.0 min, 90% B; 35.1-37.0 min, 90-20% B; 37.1-43.0 min, 20% B. The flow rate used was 4 mL / min and UV signal detection was performed at 230 nm. Product fractions of the semi-preparative HPLC were collected in 35 mL of water and passed through a C18 cartridge (Waters, pre-conditioned with 5 mL EtOH and 5 mL water). The cartridge was washed with water (5 mL) and the title compound was subsequently eluted using 0.5 mL EtOH. The radioligand 2-ethyl-2-[[6-[[(1S,2S)-2-(hydroxymethyl)cyclopropyl]methoxy]-5-(3- methoxyazetidin-1-yl)pyridine-2-carbonyl]amino]butyric acid (1,1,2,2,3,3-hexadeutero-3- (18F)fluoranyl-propyl) ester was formulated in 5% EtOH in water for injection (WFI). 2-ethyl-2-[[6-[[(1S,2S)-2-(hydroxymethyl)cyclopropyl]methoxy]-5-(3-methoxyazetidin-1-yl)pyridine-2-carbonyl]amino]butyric acid (1,1,2,2,3,3-hexadeutero-3-(18F)fluoranyl-propyl) ester was obtained with a molar activity in the range of 27-44 GBq / μmol and excellent radiochemical purity (>99%). The decay-corrected radiochemical yield was 5.0 ± 1.1%. Analytical quality control was performed on an Agilent 1100 series HPLC system equipped with a UV detector and a GabiStar radio detector (Raytest) to determine radiochemical and chemical purity, specific activity and chemical identity.Separation conditions used: RP ACE C18-AR column (50 x 4.6 mm, 3 mm) combined with 0.1% TFA in H20 (solvent A), MeCN (solvent B); 0.0-2.0 min, 20% B; 2.1-12.0 min, 20-90% B; 12.1-14.0 min, 90% B; 14.1-15.0 min, 90-20% B; 15.1-20.0 min, 20% B. The flow rate used was 1 mL / min and the UV signal was recorded at 230 nm. Molar activity was calculated by comparing the UV intensity of the formulated product to a calibration curve of the corresponding non-radioactive standard.

[0181] Example 3

[0182] 2-(1,2-Ditritioethyl)-2-[[6-[[(1 S,2S)-2-(hydroxymethyl)cyclopropyl]methoxy]-5-(3- methoxyazetidin-1 -yl)pyridine-2-carbonyl]amino]-3,4-ditritio-butyric acid 3- fluoropropyl ester

[0183]

[0184] a) 2-Ethyl-2-(6-(((1 S,2S)-2-(hydroxymethyl)cyclopropyl)methoxy)-5-(3- methoxyazetidin-1 -yl)pyridinecarboxamido)butyric acid azide

[0185]

[0186] In a 30 mL round bottom flask, 2-ethyl-2-(6-(((1 S,2S)-2- (hydroxymethyl)cyclopropyl)methoxy)-5-(3-methoxyazetidin-1 -yl)pyridinecarboxamido)butyric acid (Example 1 k, 338 mg, 802 μmol, 1 eq.) was dissolved in toluene (14 mL). Triethylamine (81 mg, 116 μL, 802 μmol, 1 eq.) and DPPA (221 mg, 173 μL, 802 μmol, 1 eq.) were added. The reaction mixture was stirred at ambient temperature for 24 h, poured onto water (20 mL) and extracted with AcOEt (3 x 30 mL). The combined organic layers were dried over sodium sulfate and concentrated in vacuo. The crude material was purified by flash chromatography (SiO2, 120 g, 10-70% AcOEt in heptane) to give the title compound (177 mg, 0.396 mmol, 48%) as an off-white solid.

[0187] 1 H NMR (600 MHz, CDC13): δ ppm 8.32 (s, 2H, NH), 7.54-7.59 (d, 1 H, J = 8.4 Hz), 7.48-7.53 (d, 1 H, J = 8.4 Hz), 6.82-6.87 (d, 1 H, J = 8.4 Hz), 5.62-5.67 (d, 1 H, J = 8.4 Hz), 4.62-4.67 (d, 1 H, J = 8.4 Hz), 4.59-4.64 (d, 1 H, J = 8.4 Hz), 4.48-4.53 (d, 1 H, J = 8.4 Hz), 4.42-4.47 (d, 1 H, J = 8.4 Hz), 4.34-4.39 (d, 1 H, J = 8.4 Hz), 4.28-4.33 (d, 1 H, J = 8.4 Hz), 4.22-4.27 (d, 1 H, J = 8.4 Hz), 4.15-4.20 (d, 1 H, J = 8.4 Hz), 3.97-4.02 (d, 1 H, J = 8.4 Hz), 3.82-3.87 (d, 1 H, J = 8.4 Hz), 3.74-3.79 (d, 1 H, J = 8.4 Hz), 3.68-3.73 (d, 1 H, J = 8.4 Hz), 3.62-3.67 (d, 1 H, J = 8.4 Hz), 3.57-3.62 (d, 1 H, J = 8.4 Hz), 3.48-3.53 (d, 1 H, J = 8.4 Hz), 3.42-3.47 (d, 1 H, J = 8.4 Hz), 3.34-3.39 (d, 1 H, J = 8.4 Hz), 3.27-3.32 (d, 1 H, J = 8.4 Hz), 3.20-3.25 (d, 1 H, J = 8.4 Hz), 3.12-3.17 (d, 1 H, J = 8.4 Hz), 2.82-2.87 (d, 1 H, J = 8.4 Hz), 2.74-2.79 (d, 1 H, J = 8.4 Hz), 2.68-2.73 (d, 1 H, J = 8.4 Hz), 2.62-2.67 (d, 1 H, J = 8.4 Hz), 2.52-2.57 (d, 1 H, J = 8.4 Hz), 2.42-2.47 (d, 1 H, J = 8.4 Hz), 2.34-2.39 (d, 1 H, J = 8.4 Hz), 2.26-2.31 (d, 1 H, J = 8.4 Hz), 2.18-2.23 (d, 1 H, J = 8.4 Hz), 2.08-2.13 (d, 1 H, J = 8.4 Hz), 1.97-2.02 (d, 1 H, J = 8.4 Hz), 1.87-1.92 (d, 1 H, J = 8.4 Hz), 1.78-1.83 (d, 1 H, J = 8.4 Hz), 1.72-1.77 (d, 1 H, J = 8.4 Hz), 1.62-1.67 (d, 1 H, J = 8.4 Hz), 1.52-1.57 (d, 1 H, J = 8.4 Hz), 1.42-1.47 (d, 1 H, J = 8.4 Hz), 1.32-1.37 (d, 1 H, J = 8.4 Hz), 1.22-1.27 (d, 1 H, J = 8.4 Hz), 1.12-1.17 (d, 1 H, J = 8.4 Hz), 0.98-1.03 (d, 1 H, J = 8.4 Hz), 0.88-0.93 (d, 1 H, J = 8.4 Hz).3 J = 7.9 Hz, 1 H, N Py -C q -CH-CH), 6.46-6.53 (d, 3 J = 7.9 Hz, 1 H, N Py -C q -CH), 4.09-4.30 (m, 8 H, m, O-CH2, CH2-N-CH2, PO 3- O-CH2, O-CH), 3.72-3.84 (m, 2 H, CH2-N-CH2), 3.23 (s, 3 H, O-CH3), 2.35-2.51 (m, 2 H, N3-CO-C q -CH2), 1.68-1.89 (m, 2 H, N3-CO-C q -CH2), 1.24-1.34 (m, 2 H, CH-CH2-CH), 0.74 (t, 3 J = 7.5 Hz, 6 H, N3-CO-C q -CH2-CH3), 0.63-0.72 (m, 2 H, CH-CH2-CH)

[0188] HRMS (ESI): C 21 H 30 N6O5 [M+H] + Theoretical = 447.2304; Found = 447.2296.

[0189] b) 6-(((1 S,2S)-2-(hydroxymethyl)cyclopropyl)methoxy)-5-(3- methoxyazetidin-1 -yl)picolinamide

[0190]

[0191] In a 25 mL round-bottom flask, 2-ethyl-2-(6-(((1 S,2S)-2- (hydroxymethyl)cyclopropyl)methoxy)-5-(3-methoxyazetidin-1 -yl)picolinamido)butyric acid azide (177 mg, 0.396 mmol, 1 eq.) was dissolved in toluene (10.0 mL). The reaction mixture was heated to 110 °C for 3 h with stirring, then concentrated in vacuo. THF (3 mL) and 3 N NaOH (7 mL) were added. The reaction mixture was heated to 90 °C for 1 h with stirring, poured onto water (10 mL) and extracted with AcOEt (3 x 40 mL). The combined organic layers were dried over sodium sulfate and concentrated in vacuo to give the title compound (85 mg, 0.277 mmol, 70%) as a light orange oil. The crude material was used in the next step without further purification.

[0192] 1 H NMR (600 MHz, CDC13): δ ppm 8.18 (CO-NH2), 7.74 (d, 3 J = 8.0 Hz, 1 H, N Py -C q -CH-CH), 6.56 (d, 3 J = 8.0 Hz, 1 H, N Py -C q -CH), 3.99-4.41 (m, 7 H, O-CH2, CH2-N-CH2, O-CH, HO-CH2), 3.95 - 4.00 (m, 2 H, CH2-N-CH2), 3.29 (m, 3 H, O-CH3), 1.20 - 1.36 (CH-CH2-CH), 0.54-0.79 (m, 2 H, CH-CH2-CH)

[0193] MS (ESI): C 15 H 21 N3O4[M+H] + Theoretical = 308.14; Found = 308.20.

[0194] c) 6-(((1S,2S)-2-(hydroxymethyl)cyclopropyl)methoxy)-5-(3- methoxyazetidin-1-yl)picolinic acid

[0195]

[0196] In a 25 mL round-bottom flask, 6-(((1S,2S)-2-(hydroxymethyl)cyclopropyl)methoxy)-5-(3- methoxyazetidin-1-yl)picolinic acid amide (85 mg, 0.277 mmol, 1 eq.) was dissolved in methanol (3 mL) and water (5 mL). Sodium hydroxide (55 mg, 1.38 mmol, 5 eq.) was added. The reaction mixture was heated to 85 °C for 12 h with stirring, poured onto water (10 mL) and 1 N HC1 (3 mL) and extracted with AcOEt (3 x 20 mL). The combined organic layers were dried over sodium sulfate and concentrated in vacuo. The crude product was purified by flash chromatography (SiO2, 12 g, 40-100% AcOEt in heptane) to give the title compound (64 mg, 0.207 mmol, 75%) as a light orange solid.

[0197] 1 H NMR (600 MHz, CDC13): δ ppm 7.72 (dd, 3 J = 7.9 Hz, 4 J = 2.9 Hz, 1 H, N Py -C q-CH-CH), 6.56 (d, 3 J = 7.9 Hz, 1H, N Py -C q -CH), 3.99-4.41 (m, 7H, O-CH2, CH2-N-CH2, O-CH, HO-CH2), 3.97– 3.99 (m, 2H, CH2-N-CH2), 3.28 (m, 3H, O-CH3), 1.18– 1.32 (CH-CH2-CH), 0.56– 0.81 (m, 2H, CH-CH2-CH)

[0198] HRMS (ESI): C 15 H 20 N2O5[M+H] + Theoretical = 309.1379; Experimental = 309.1451.

[0199] d) 2-[[6-[[(1S,2S)-2-(hydroxymethyl)cyclopropyl]methoxy]-5-(3- methoxyazetidin-1-yl)pyridine-2-carbonyl]amino]-2-ethenyl-but-3-enoic acid 3- fluoropropyl ester

[0200]

[0201] To a round bottom flask was added 3-fluoroprop-1-ol (1.55 g, 1.61 mL, 19.8 mmol, Eq.: 18) and 2-amino-2-ethenylbut-3-enoic acid hydrochloride (CAN 1865695-91-5, 180 mg, 1.1 mmol, Eq.: 1). Sulfur dichloride (1.31 g, 798 μL, 11 mmol, Eq.: 10) was added. The reaction mixture was stirred at 80 °C for 1 h, poured into water (10 mL) and extracted with CH2Cl2(2 x 20 mL). The organic layers were combined, dried over sodium sulfate, filtered and concentrated in vacuo. The crude was purified by flash chromatography (silica gel, 12 g, 20% to 70% AcOEt in heptane) to give the title compound as a colorless oil, LC-MS (UV peak area / ESI) 94%, 187.1083 [MH + ].

[0202] e) 2-[[6-[[(1S,2S)-2-(hydroxymethyl)cyclopropyl]methoxy]-5-(3- methoxyazetidin-1-yl)pyridine-2-carbonyl]amino]-2-ethenyl-but-3-enoic acid 3- fluoropropyl ester

[0203]

[0204] (1.34 mL). N-ethyl-N-isopropylpropan-2-amine (41.4 mg, 55.2 μL, 320 μmol, Eq.: 4) was added followed by 1 -(bis(dimethylamino)methylene)-1 H- [1,2,3]triazolo[4,5-b]pyridinium 1 -oxide hexafluorophosphate (V) (36.6 mg, 96.1 μmol, Eq.: 1.2). The reaction mixture was stirred at ambient temperature for 1 h, poured onto water (10 mL) and extracted with CH2Cl2(4 x 20 mL). The organic layers were combined, dried over sodium sulfate, filtered and concentrated in vacuo. The crude material was purified by flash chromatography (silica gel, 12 g, 20% to 70% AcOEt in heptane) to give the title compound as a colorless oil, LC-MS (UV peak area / ESI) 98%, 478.2399 [MH + ] at t = 2.48 min.

[0205] f) 2-(1,2-Ditritioethyl)-2-[[6-[[(1 S,2S)-2-(hydroxymethyl)cyclopropyl]methoxy]-5-(3- methoxyazetidin-1 -yl)pyridine-2-carbonyl]amino]-3,4-ditritio-butanoic acid 3- fluoropropyl ester

[0206] In a 2 ml titration flask, 2-[[6-[[(1S,2S)-2-(hydroxymethyl)cyclopropyl]methoxy]-5-(3- methoxyazetidin-1-yl)pyridine-2-carbonyl]amino]-2-vinyl-but-3-enoic acid 3-fluoropropyl ester (2.0 mg, 4.2 pmol, 1.0 eq.) and Pd / C (10%) (0.89 mg, 0.84 pmol, 0.2 eq.) were suspended in dimethylformamide (0.4 ml). The flask was connected to a tritium manifold (RC-TRITEC) and degassed by freeze-pump-thaw. Tritium gas was introduced and the black suspension was stirred vigorously for 3 hours under a tritium atmosphere of 560 mbar. The solution was cooled by liquid nitrogen and the excess tritium gas in the reaction vessel was resorbed onto a uranium trap for waste tritium gas. The solvent was lyophilized and the labile tritium gas was removed by lyophilization with methanol (3 x 1 ml). The remaining black residue was suspended in methanol (10 ml) and filtered over a 17 mm Titan HPLC filter (0.45 pm, PTFE) to give 8.21 GBq (222 mCi) of the crude product with a purity > 90%. The crude product was concentrated and purified by preparative HPLC (SunFire C18, 5 pm, 4.6 x 250 mm) with acetonitrile [A] and 5% acetonitrile in water [B] as eluent (gradient: 10% [A], 90% [B] to 99% [A], 1% [B] in 12 min, hold for 3 min, then for 5 min back to initial conditions). 4.59 GBq (124 mCi) of the title compound were obtained with a radiochemical purity of 98.7% and a specific activity of 4.18 TBq / mmol (113 Ci / mmol) as determined by MS spectroscopy. The compound was stored as an ethanol solution. MS m / z: 482.3 [M+H] + (1%), 484.3 [M 3 H]+H] + (5%), 486.3 [M 3 H2]+H] + (13%), 488.3 [M 3 H3]+H] + (21%), 490.3 [M 3 H4]+H] + (12%), 492.3 [M 3 H5]+H] + (20%), 494.3 [M 3 H6]+H] + (12%), 496.3 [M 3 H7]+H] + (4%).

[0207] Example 4

[0208] Radioligand binding assays and microPET studies

[0209] Stably transfected cells or spleen tissue were homogenized in 15 mmol L"1Hepes, 0.3 mmol L"1EDTA, 1 mmol L"1EGTA, 2 mmol L"1MgCl2, complete EDTA-free protease inhibitor (Roche Applied Science, Rotkreuz, Switzerland) (pH 7.4) using a glass pot and centrifugation at 47,800 g for 30 min at 4°C. The pellets were then homogenized twice and centrifuged (47,800 g, 4°C, 30 min) in the same buffer. The final pellets were then resuspended in 75 mmol L"1Tris, 0.3 mmol L"1EDTA, 1 mmol L"1EGTA, 12.5 mmol L"1MgCl2, 250 mmol L"1sucrose (pH 7.4) at a protein concentration of 1 to 3 mg mL"1, aliquoted, frozen on dry ice and stored at -80°C.

[0210] Saturation binding was performed with 0.05 to 2.4 nM of compound of formula (I) and 40 μg of membrane protein. CP 55940 (10 μM) was used to define non-specific binding. The assay buffer consisted of 50 mmol L"1Tris-HCl, 5 mmol L"1MgCl2, 2.5 mmol L"1EGTA and 0.1 % fatty acid free BSA (pH 7.4). The assay was started by adding the membranes in a final volume of 250 μl / well. The assay was incubated for 2 h at room temperature on a Filtermate cell harvester on Packard GF / B filters pre-soaked in 0.3 % polyethyleneimine, then vacuum filtered and rinsed with wash buffer (50 mmol L"1Tris-HCl, 5 mmol L"1MgCl2, 2.5 mmol L"1EGTA and 0.5 % fatty acid free BSA, pH 7.4).

[0211] For competition binding, membrane preparations were incubated with 0.3 nM of [3H]CP 55940 in the presence or absence of increasing concentrations of unlabeled compound of formula (I) in a final volume of 0.2 mL of 50 mmol L"1Tris-HCl, 5 mmol L"1MgCl2, 2.5 mmol L"1EGTA, 0.1 % fatty acid free BSA and 1 % DMSO (pH 7.4) buffer, gently shaken at 30°C. The assay was terminated by filtration through glass fiber filters (GF / B, Whatman) soaked in 0.3 % polyethyleneimine and washed with ice-cold wash buffer (50 mmol L"1Tris-HCl, 5 mmol L"1MgCl2, 2.5 mmol L"1EGTA and 0.5 % fatty acid free BSA, pH 7.4). The radioactivity trapped on the filters was counted in a Packard Tri-Carb 2800TR liquid scintillation counter. 1 = R 2 = CH2CH3, R 3 = CH2CH2CH2F) compound.3 H]-CP55940 incubation, or in the presence or absence of CP55940 (10 μM), with 1.5 nM of the compound of formula (I) ((R 1 = R 2 = CHTCH2T, R 3 = CH2CH2CH2F)) and increasing amounts of membranes (2.5 - 80 μg) for 60 min. All binding reactions were terminated by vacuum filtration on 0.5% polyethyleneimine pre-soaked GF / B filters (Packard) followed by seven brief washes with 2 mL ice-cold binding buffer containing 0.5% fatty acid-free BSA. Plates were dried at 50°C for 1 h and bound radio-label was determined using liquid scintillation counting. IC50values and Hill slopes were determined by a four-parameter logistic model using ActivityBase (ID Business Solution, Ltd.).

[0212] The results are shown in Table 1 and Figure 1 .

[0213] Figure 1 : Time activity curve of rat spleen and muscle after intravenous (iv) administration of 2-ethyl-2-[[6-[[(1S,2S)-2-(hydroxymethyl)cyclopropyl]methoxy]-5-(3-methoxyazetidin-1-yl)pyridine-2-carbonyl]amino]butyric acid 18 F] 3-fluoropropyl ester (Example 1, non-deuterated) and 2-ethyl-2-[[6-[[(1S,2S)-2- (hydroxymethyl)cyclopropyl]methoxy]-5-(3-methoxyazetidin-1-yl)pyridine-2-carbonyl]amino]butyric acid 18 F] (1,1,2,2,3,3-hexadeuterated-3-fluoro-propyl) ester (Example 2, deuterated). Displacement in the tracer experiment was performed by administration of GW405833 (CAS 180002-83-9) (iv, 1.5 mg / kg) 10 min after tracer injection.

[0214] Table 1

[0215] Radioligand competition binding of [3H]-CP55940 using CHO-K1 cells expressing human CB2 receptors 3 H]CP55940 incubation, or in the presence or absence of CP55940 (10 μM), with 1.5 nM of the compound of formula (I) ((R

[0216] Human CB1 Human CB2

[0217] Ki [nM] >10’000 0.7

[0218] Table 1 shows that in cells recombinantly expressing these receptors and using the non-selective CB1 / CB2 radioligand 3H] The high binding selectivity of the unlabeled compound of formula (I) for human CB2 receptors (Ki 0.7 nM) over human CB1 receptors (Ki > 10'000 nM) for CP 55940.

Claims

1. A compound of formula (I) ###0001### wherein A is CH; or a pharmaceutically acceptable salt thereof. (I) 4. Use of a compound according to any one of claims 1 to 3 in the manufacture of a medicament for localizing CB2 receptors in a patient or sample.

5. Use of a compound according to any one of claims 1 to 3 in the manufacture of a medicament for imaging CB2 receptors in a patient or sample. R 1 and R 2 both are -C 3 HH-C 3 HH2; and R 3 is a fluoropropyl or hexadeuterated fluoropropyl group; with the proviso that at least one of R 1 , R 2 and R 3 comprises at least one radionuclide, and wherein the at least one radionuclide is independently selected from the group consisting of [ 3 H], [ 18 F] and [ 11 C]; 6. Use of a compound according to any one of claims 1 to 3 in the manufacture of a medicament for determining whether a further compound binds to CB2 receptors.

2. The compound of claim 1, wherein R 3 contains a radionuclide.

3. The compound of claim 1, wherein R 3 is -CH2-CH2-CH2 18 F or -CD2-CD2-CD2 18 F.

7. Use according to claim 6 further comprising measuring the binding constant of the further compound to the CB2 receptor.

8. Use according to claim 6 or 7 which is carried out in the presence of CB1 receptors.

9. Use of a compound according to any one of claims 1 to 3 in the manufacture of a medicament for determining whether a disease is characterized by a change in expression of CB2 receptors.

10. Use according to claim 9 wherein the disease is pain, atherosclerosis, age-related macular degeneration, diabetic retinopathy, glaucoma, diabetes, inflammation, ischaemia-reperfusion injury, acute liver failure, liver fibrosis, lung fibrosis, kidney fibrosis, systemic fibrosis, acute allograft rejection, chronic allograft nephropathy, diabetic nephropathy, glomerulonephropathy, cardiomyopathy, heart failure, myocardial ischaemia, myocardial infarction, systemic sclerosis, thermal injury, burn injury, hypertrophic scarring, keloid scarring, gingivitis pyrexia, cirrhosis or tumour, bone mass regulation, neurodegeneration, stroke or transient ischaemic attack.

11. Use according to claim 9 wherein the disease is inflammatory bowel disease or uveitis.

12. A compound according to claim 1 or 2 for use in diagnosing a disease in a patient or tissue.

13. A compound according to claim 12 wherein the disease is characterized by a change in expression of CB2 receptors in the patient or tissue compared to the expression of CB2 receptors in a healthy subject or tissue.

14. Comparing the expression of CB2 receptors in the patient or tissue to the expression of CB2 receptors in a healthy subject or tissue.

15. Use of a compound according to any one of claims 1 to 3 in the manufacture of a medicament for predicting whether a patient affected by a disease is likely to respond to a treatment involving the administration of a CB2 ligand.

16. Use according to claim 15 comprising comparing the expression of CB2 receptors in the patient to the expression of CB2 receptors in a healthy subject or tissue.

14. The compound of claim 12, wherein the diagnosing comprises the steps of:

17. Use of a compound according to any one of claims 1 to 3 in the manufacture of a medicament for assessing the efficacy of a medical treatment in a patient, comprising monitoring the density of CB2 receptors in the patient before, during and / or after the medical treatment.

18. Use of a compound according to any one of claims 1 to 3 in the manufacture of a medicament for determining the dose of a CB2 ligand required for administration to a patient in need thereof. ​ ​ ​ 19. A method for identifying a compound that binds to CB2 receptors for diagnostic and therapeutic purposes other than disease, the method comprising the steps of: (a) contacting a compound suspected of binding to CB2 receptors with a sample comprising CB2 receptors and a compound according to any one of claims 1 to 3; and (b) monitoring whether the compound suspected of binding to CB2 receptors affects the binding of the compound according to any one of claims 1 to 3 to the CB2 receptors.

20. The method of claim 19, further comprising the step of measuring the strength of binding of the compound suspected of binding to CB2 receptors to the CB2 receptors.

21. The method of claim 20, further comprising the step of measuring the binding constant of the compound suspected of selectively binding to CB2 receptors to the CB2 receptors.

22. A method for identifying a cellular receptor that is a CB2 receptor for diagnostic and therapeutic purposes other than disease, the method comprising the steps of: (a) contacting a sample suspected of comprising CB2 receptors with a compound according to any one of claims 1 to 3; and (b) monitoring whether binding of the compound according to any one of claims 1 to 3 occurs; and (c) optionally further contacting the sample with an additional known CB2 ligand and monitoring whether the known CB2 ligand has displaced the compound according to any one of claims 1 to 3 from its binding site.

23. A method for measuring the percentage of CB2 receptors in a sample that are occupied by a compound suspected of binding to CB2 receptors when the compound is contacted with the sample for diagnostic and therapeutic purposes other than disease, the method comprising the steps of: (a) contacting a sample comprising at least one CB2 receptor with a compound according to any one of claims 1 to 3 to determine a baseline signal; (b) contacting the sample with a dose of the compound suspected of binding to the CB2 receptors and a compound according to any one of claims 1 to 3; (c) monitoring displacement of the compound according to any one of claims 1 to 3 by the compound suspected of binding to CB2 receptors; and (d) calculating the percentage of the CB2 receptors that are occupied by the compound suspected of binding to CB2 receptors.

24. A pharmaceutical composition comprising a compound according to any one of claims 1 to 3.

25. A compound according to claim 1 or 2 for use as a diagnostic agent.

26. A compound according to claim 1 or 2 for use in the diagnosis of pain, atherosclerosis, age-related macular degeneration, diabetic retinopathy, glaucoma, diabetes, inflammation, ischemia-reperfusion injury, acute liver failure, liver fibrosis, lung fibrosis, kidney fibrosis, systemic fibrosis, acute allograft rejection, chronic allograft nephropathy, diabetic nephropathy, glomerulonephropathy, cardiomyopathy, heart failure, myocardial ischemia, myocardial infarction, systemic sclerosis, thermal injury, burn injury, hypertrophic scarring, keloid scarring, gingivitis pyrexia, cirrhosis or tumors, bone mass regulation, neurodegeneration, stroke or transient ischemic attack.

27. A compound according to claim 1 or 2 for use in the diagnosis of inflammatory bowel disease or uveitis.

28. A process for the preparation of a compound according to any one of claims 1 to 3, said process comprising one of the following steps: (a) reacting a compound of formula (A) (A) with nucleophiles 18 F] fluoride reagents; or (b) reacting a compound of formula (B) (B) and[ 3 H]2 reaction; wherein LG is a leaving group and wherein R 1 to R 3 as defined in any one of claims 1 to 3.

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