RU2021105534A - NEW HETEROCYCLIC COMPOUNDS AS MONOACYLGLYCEROL LIPASE INHIBITORS - Google Patents

Claims (166)

1. Compound of formula (I)

or a pharmaceutically acceptable salt thereof, where: X is CR ³ ; m is 0 or 1; n is selected from 0, 1 and 2; and L is selected from -C≡C-, -CHR ⁴ -NR ⁵ -CH ₂ -, -NR ⁵ -CH ₂ -CHR ⁴ -, -NR ⁵ -CHR ⁴ -CH ₂ -, -CH ₂ -NR ⁵ - CHR ⁴ -, -(CR ⁶ R ⁷ ) _p -C(O)-NR ⁸ -, -C(O)-NR ⁸ -(CR ⁶ R ⁷ ) _p -, -(CR ⁶ R ⁷ ) _p -NR ⁸ -C(O)-, -NR ⁸ -C(O)-(CR ⁶ R ⁷ ) _p -, -(CH ₂ ) _q NR ⁹ -, -NR ⁹ -(CH ₂ ) _q -, -S- , -S(O)-, -SO ₂ -, SCH _2, -CH ₂ S-, -S(O)CH ₂ -, -CH ₂ S(O)-, -SO ₂ CH ₂ - and -CH _{2 SO2-} ; or X is N; m is 1; n is 1 or 2; and L is selected from -NR ⁵ -CH ₂ - CHR ⁴ -, -NR ⁵ -CHR ⁴ -CH ₂ - and -NR ⁸ -C(O)-(CR ⁶ R ⁷ ) _p -; each of p and q is independently selected from 0, 1 and 2; And selected from: (i) C ₆ -C ₁₄ aryl substituted with R ¹⁰ , R ¹¹ and R ¹² ; (ii) 5-14 membered heteroaryl substituted with R ¹³ , R ¹⁴ and R ¹⁵ ; and (iii) 3 14-membered heterocycloalkyl substituted with R ¹⁶ , R ¹⁷ and R ¹⁸ ; (iv) C ₃ -C ₁₀ cycloalkyl substituted with R ²² , R ²³ and R ²⁴ ; R ¹ is hydrogen or C _1-6 alkyl; R ² is selected from hydrogen, C _1-6 -alkyl and hydroxy-C _1-6 -alkyl; R ³ is selected from hydrogen, halogen, hydroxy, C _1-6 alkoxy, C _1-6 alkyl and halo-C _1-6 alkyl; R ⁴ is selected from hydrogen, C _1-6 -alkyl and halo-C _1-6 -alkyl; R ⁵ is selected from hydrogen, C _1-6 -alkyl and halo-C _1-6 -alkyl-CH ₂ -; each of R ⁶ and R ⁷ independently represents hydrogen or C _1-6 -alkyl; or R ⁶ and R ⁷ together with the carbon atom to which they are attached form a 3-14-membered heterocycloalkyl or C _3-10 -picloalkyl; R ⁸ is selected from hydrogen, C _1-6 alkyl and hydroxy-C _1-6 alkyl; R ⁹ is selected from hydrogen, C _1-6 -alkyl, halo-C _1-6 -alkyl-CH ₂ -, (C _1-6 -alkyl) (halo-C _1-6 -alkyl) CH - and hydroxy-C _1-6 -alkyl-CH ₂ -; each of R ¹⁰ , R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , R ¹⁶ , R ¹⁷ and R ¹⁸ is independently selected from hydrogen, halogen, cyano, hydroxy, C _1-6 -alkyl, halo-C _{1 -6} -alkyl, hydroxy-C _1-6 -alkyl, halogen-C _1-6 -alkyl-CH (OH) -, C _1-6 -alkoxy, C _1-6 -alkoxy-C _1-6 -alkyl, halogen-C _1-6 -alkoxy, SF ₅ , C _1-6 -alkylsulfonyl, C _3-10 -cycloalkyl, C _3-10 -cycloalkyl substituted with R ¹⁹ , 3-14-membered heterocycloalkyl, 3-14-membered heterocycloalkyl , substituted by R ²⁰ , 5-14-membered heteroaryl, C ₆ -C ₁₄ -aryl and halo-C ₆ -C ₁₄ -aryl; and each of R ¹⁹ and R ²⁰ is independently selected from C _1-6 alkyl, cyano and hydroxy. 2. The compound of formula (I) according to claim 1, or a pharmaceutically acceptable salt thereof, wherein the compound of formula (I) is a compound of formula (Ia)

, while A, L, X, m, n, R ¹ and R ² are as described in paragraph 1. 3. The compound of formula (I) according to claim 1, or a pharmaceutically acceptable salt thereof, wherein the compound of formula (I) is a compound of formula (Ib)

, while A, L, X, m, n, R ¹ and R ² are as described in paragraph 1. 4. The compound of formula I according to any one of paragraphs. 13 or a pharmaceutically acceptable salt thereof, where X is CR ³ ; each of m and n is independently 0 or 1; and L is selected from -C≡C-, -CHR ⁴ -NR ⁵ -CH ₂ -, -CH ₂ -NR ⁵ -CHR ⁴ -, -(CR ⁶ R ⁷ ) _p -C(O) -NR ⁸ -, -(CR ⁶ R ⁷ ) _p -NR ⁸ -C(O)-, -(CH ₂ ) _q NR ⁹ -, -S-, -S(O)-, -SO ₂ - -SCH ₂ - -CH ₂ S--S(O)CH ₂ - -CH ₂ S(O)-, -SO ₂ CH ₂ - and -CH ₂ SO ₂ -. 5. The compound of formula I according to any one of paragraphs. 1-4 or a pharmaceutically acceptable salt thereof, where X is CR ³ ; m and n are both 0; or m and n are both 1; and L is selected from -C≡C-, -CHR ⁴ -NR ⁵ -CH ₂ -, -(CH ₂ ) _q NR ⁹ -, -SCH ₂ - and -CH ₂ S-. 6. The compound of formula I according to any one of paragraphs. 1-5 or a pharmaceutically acceptable salt thereof, where p is 0 or 1. 7. The compound of formula I according to any one of paragraphs. 1-6 or a pharmaceutically acceptable salt thereof, where q is 0. 8. The compound of formula I according to any one of paragraphs. 1-7 or a pharmaceutically acceptable salt thereof, where A is selected from (i) C ₆ -C ₁₄ aryl substituted with R ¹⁰ , R ¹¹ and R ¹² ; (ii) 5-14 membered heteroaryl substituted with R ¹³ , R ¹⁴ and R ¹⁵ ; and (iii) C ₃ -C ₁₀ cycloalkyl substituted with R ²² , R ²³ and R ²⁴ . 9. The compound of formula I according to any one of paragraphs. 1-7 or a pharmaceutically acceptable salt thereof, wherein A is C ₆ -C ₁₄ aryl substituted with R ¹⁰ , R ¹¹ and R ¹² . 10. The compound of formula I according to any one of paragraphs. 1-7 or a pharmaceutically acceptable salt thereof, wherein A is phenyl substituted with R ¹⁰ , R ¹¹ and R ¹² . 11. The compound of formula I according to any one of paragraphs. 1-10 or a pharmaceutically acceptable salt thereof, wherein R ¹ is hydrogen. 12. The compound of formula I according to any one of paragraphs. 1-11 or a pharmaceutically acceptable salt thereof, wherein R is hydrogen. 13. The compound of formula I according to any one of paragraphs. 1-12 or its pharmaceutically acceptable salt, where R represents hydrogen, hydroxy or C _1-6 -alkyl. 14. The compound of formula I according to any one of paragraphs. 1-12 or a pharmaceutically acceptable salt thereof, wherein R is hydrogen. 15. The compound of formula I according to any one of paragraphs. 1-14 or a pharmaceutically acceptable salt thereof, wherein R ⁴ is halo-C _1-6 alkyl. 16. The compound of formula I according to any one of paragraphs. 1-14 or a pharmaceutically acceptable salt thereof wherein R ⁴ is CF ₃ . 17. The compound of formula I according to any one of paragraphs. 1-16 or a pharmaceutically acceptable salt thereof, wherein R ⁵ is hydrogen. 18. The compound of formula I according to any one of paragraphs. 1-17 or a pharmaceutically acceptable salt thereof, where R ⁶ and R ⁷ are both hydrogen; or R ⁶ and R ⁷ together with the carbon atom to which they are attached form C _3-10 cycloalkyl. 19. The compound of formula I according to any one of paragraphs. 1-18 or a pharmaceutically acceptable salt thereof, wherein R ⁹ is C _1-6 alkyl. 20. The compound of formula I according to any one of paragraphs. 1-18 or a pharmaceutically acceptable salt thereof wherein R ⁹ is methyl. 21. The compound of formula I according to any one of paragraphs. 1-20 or a pharmaceutically acceptable salt thereof, where R ¹⁰ is hydrogen, C _1-6 -alkyl, C _1-6 -alkylsulfonyl, C _1-6 -alkoxy, halogen-C _1-6 -alkyl, halogen-C _{1 -6} -alkoxy, C _1-6 -alkoxy-C _1-6 -alkyl, C _3-10 -cycloalkyl, C _3-10 -cycloalkyl, substituted with R ¹⁹ , cyano or halogen. 22. The compound of formula I according to any one of paragraphs. 1-20 or a pharmaceutically acceptable salt thereof, wherein R ¹⁰ is C _1-6 alkyl, halo-C _1-6 alkyl, halo-C _1-6 alkoxy, C _3-10 cycloalkyl, or halogen. 23. The compound of formula I according to any one of paragraphs. 1-20 or a pharmaceutically acceptable salt thereof, wherein R ¹⁰ is methyl, difluoromethyl, CF ₃ , OCF ₃ , cyclopropyl, fluorine or chlorine. 24. The compound of formula I according to any one of paragraphs. 1-23 or a pharmaceutically acceptable salt thereof, wherein R ¹¹ is hydrogen, C _1-6 alkyl or halogen. 25. The compound of formula I according to any one of paragraphs. 1-23 or its pharmaceutically acceptable salt, where R ¹¹ represents hydrogen, methyl, chlorine or fluorine. 26. The compound of formula I according to any one of paragraphs. 1-25 or a pharmaceutically acceptable salt thereof, wherein R ¹² is hydrogen or halogen. 27. The compound of formula I according to any one of paragraphs. 1-25 or a pharmaceutically acceptable salt thereof, wherein R ¹² is hydrogen or fluorine. 28. The compound of formula I according to any one of paragraphs. 1-27 or a pharmaceutically acceptable salt thereof, wherein R ¹³ is halogen. 29. The compound of formula I according to any one of paragraphs. 1-28 or a pharmaceutically acceptable salt thereof, wherein R ¹⁴ is hydrogen. 30. The compound of formula I according to any one of paragraphs. 1-29 or a pharmaceutically acceptable salt thereof, wherein R ¹⁵ is hydrogen. 31. The compound of formula I according to any one of paragraphs. 1-30 or a pharmaceutically acceptable salt thereof, wherein R ¹⁹ is hydroxy or cyano. 32. The compound of formula I according to any one of paragraphs. 1-31 or a pharmaceutically acceptable salt thereof, wherein R ²² is hydrogen or hydroxy. 33. The compound of formula I according to any one of paragraphs. 1-32 or a pharmaceutically acceptable salt thereof, wherein R ²³ is hydrogen. 34. The compound of formula I according to any one of paragraphs. 1-33 or a pharmaceutically acceptable salt thereof, wherein R ²⁴ is hydrogen. 35. The compound of formula I according to any one of paragraphs. 1-3 or a pharmaceutically acceptable salt thereof, where X is CR ³ ; L is selected from -C≡C-, -CHR ⁴ -NR ⁵ -CH ₂ -, -CH ₂ -NR ⁵ -CHR ⁴ -, -(CR ⁶ R ⁷ ) _p -C(O)-NR ⁸ -, - (CR ⁶ R ⁷ ) _p -NR ⁸ -C(O)-, -(CH ₂ ) _q NR ⁹ -, -S-, -S(O)-, -SO ₂ -, -SCH ₂ -, -CH ₂ S-, -S(O)CH ₂ -, -CH ₂ S(O)- and -SO ₂ CH ₂ -; each of m, n and p is independently 0 or 1; q is 0; And selected from (i) C ₆ -C ₁₄ aryl substituted with R ¹⁰ , R ¹¹ and R ¹² ; (ii) 5-14-heteroaryl substituted with R ¹³ , R ¹⁴ and R ¹⁵ ; and (iii) C ₃ -C ₁₀ cycloalkyl substituted with R ²² , R ²³ and R ²⁴ ; R ¹ and R ² are both hydrogen; R ³ is selected from hydrogen, hydroxy and C _1-6 alkyl; R ⁴ is halo-C _1-6 alkyl; R ⁵ is hydrogen or C _1-6 alkyl; R ⁶ and R ⁷ are both hydrogen; or R ⁶ and R ⁷ together with the carbon atom to which they are attached form C _3-10 cycloalkyl; R ⁸ is selected from hydrogen, C _1-6 alkyl and hydroxy-C _1-6 alkyl; R ⁹ is C _1-6 alkyl; R ¹⁰ is selected from hydrogen, C _1-6 -alkyl, C _1-6 -alkylsulfonyl, C _1-6 -alkoxy, C _1-6 -alkoxy-C _1-6 -alkyl, halo-C _1-6 -alkyl, halo-C _1-6 alkoxy, C _3-10 cycloalkyl, C _3-10 cycloalkyl substituted with R ¹⁹ , cyano and halogen; R ¹¹ is selected from hydrogen, C _1-6 -alkyl and halogen; R ¹² is hydrogen or halogen; R ¹³ is halogen; R ¹⁴ and R ¹⁵ are both hydrogen; R ¹⁹ is hydroxy or cyano; R ²² is hydrogen or hydroxy; and R ²³ and R ²⁴ are both hydrogen. 36. The compound of formula I according to any one of paragraphs. 1-3, where X is CR ³ ; L is selected from C=C, -CHR ⁴ -NR ⁵ -CH ₂ -, -(CH ₂ ) _q NR ⁹ -, -SCH ₂ - and CH ₂ S; m and n are both 0; or m and n are both 1; q is 0; A represents C ₆ -C ₁₄ aryl substituted with R ¹⁰ , R ¹¹ and R ¹² ; R ¹ , R ² and R ³ are all hydrogen; R ⁴ is halo-C _1-6 alkyl; R ⁵ is hydrogen; R ⁹ is C _1-6 alkyl; R ¹⁰ is selected from C _1-6 alkyl, halo-C _1-6 alkyl, halo-C _1-6 alkoxy, C _3-10 cycloalkyl and halogen; R ¹¹ is selected from hydrogen, C _1-6 -alkyl and halogen; and R ¹² is hydrogen or halogen. 37. The compound of formula I according to any one of paragraphs. 1-3, where X is CR ³ ; L is selected from -C≡C-, -CHR ⁴ -NR ⁵ -CH ₂ -, -(CH ₂ ) _q NR ⁹ -, -SCH ₂ - and -CH ₂ S-; m and n are both 0; or m and n are both 1; q is 0; A is phenyl substituted with R ¹⁰ , R ¹¹ and R ¹² ; R ¹ , R ² and R ³ are all hydrogen; R ⁴ is CF ₃ ; R ⁵ is hydrogen; R ⁹ is methyl; R ¹⁰ is selected from methyl, difluoromethyl, CF ₃ , OCF ₃ , cyclopropyl, chlorine and fluorine; R ¹¹ is selected from hydrogen, methyl, chlorine and fluorine; and R ¹² represents hydrogen or fluorine. 38. The compound of formula (I) according to any one of paragraphs. 1-37 selected from the compounds disclosed in Table 1. 39. A compound of formula (I) selected from (+)- or (-)-(4aR,8aS)-6-[3-[[[2,2,2-trifluoro-1-[4-(trifluoromethyl)phenyl]ethyl]amino]methyl]azetidine-1 -carbonyl]hexahydro-2H-pyrido[4,3-b][1,4]oxazin-3(4H)-one; (4aR,8aS)-6-[4-[2-(2-chlorophenyl)ethynyl]piperidine-1-carbonyl]-4,4a,5,7,8,8a-hexahydropyrido[4,3-b][1 ,4]oxazin-3-one; (+)- or (-)-(4aR,8aS)-6-[4-[2-(2-chloro-4-fluorophenyl)ethynyl]piperidine-1-carbonyl]-4,4a,5,7,8 ,8a-hexahydropyrido[4,3-b][1,4]oxazin-3-one; (4aR,8aS)-6-[3-[2-(2-chlorophenyl)ethynyl]azetidine-1-carbonyl]-4,4a,5,7,8,8a-hexahydropyrido[4,3-b][1 ,4]oxazin-3-one; (4aR,8aS)-6-[3-[2-(2-chloro-4-fluorophenyl)ethynyl]azetidine-1-carbonyl]-4,4a,5,7,8,8a-hexahydropyrido[4,3- b][1,4]oxazin-3-one; (4aR,8aS)-6-[4-[N-methyl-4-(trifluoromethyl)anilino]piperidine-1-carbonyl]-4,4a,5,7,8,8a-hexahydropyrido[4,3-b] [1,4]oxazin-3-one; (4aR,8aS)-6-(3-(((2-chloro-4-(trifluoromethyl)phenyl)thio)methyl)azetidine-1-carbonyl)hexahydro-2Н-pyrido[4,3-b] [1, 4]oxazin-3(4H)-one; (4aR,8aS)-6-(3-((2-fluoro-4-(trifluoromethyl)benzyl)thio)azetidine-1-carbonyl)hexahydro-2H-pyrido[4,3-b][1,4]oxazine -3(4H)-she; (4aR,8aS)-6-(3-((2,6-dichlorophenyl)ethynyl)azetidine-1-carbonyl)hexahydro-2H-pyrido[4,3-b][1,4]oxazine-3(4H) -she is; (4aR,8aS)-6-[3-[2-[2-fluoro-4-(trifluoromethyl)phenyl]ethynyl]azetidine-1-carbonyl]-4,4a,5,7,8,8a-hexahydropyrido[4 ,3-b][1,4]oxazin-3-one; (4aR,8aS)-6-(3-((2-chloro-6-fluorophenyl)ethynyl)azetidine-1-carbonyl)hexahydro-2Н-pyrido[4,3-b][1,4]oxazine-3( 4H) - she; (4aR,8a8)-6-(3-((2-chloro-4-cyclopropylphenyl)ethynyl)azetidine-1-carbonyl)hexahydro-2H-pyrido[4,3-b][1,4]oxazine-3( 4H) - she; (4aR,8aS)-6-[3-[2-[4-trifluoromethoxy)phenyl]ethynyl]azetidine-1-carbonyl]-4,4a,5,7,8,8a-hexahydropyrido[4,3-b] [1,4]oxazin-3-one; (4aR,8aS)-6-[3-[2-(2,6-dimethylphenyl)ethynyl]azetidine-1-carbonyl]-4,4a,5,7,8,8a-hexahydropyrido[4,3-b] [1,4]oxazin-3-one; (4aR,8aS)-6-[3-[2-[2-(trifluoromethoxy)phenyl]ethynyl]azetidine-1-carbonyl]-4,4a,5,7,8,8a-hexahydropyrido[4,3-b ][1,4]oxazin-3-one; (4aR,8aS)-6-(3-(o-tolylethynyl)azetidine-1-carbonyl)hexahydro-2H-pyrido[4,3-b][1,4]oxazin-3(4H)-one; (4aR,8aS)-6-[3-[2-(4-chloro-2-fluorophenyl)ethynyl]azetidine-1-carbonyl]-4,4a,5,7,8,8a-hexahydropyrido[4,3- b][1,4]oxazin-3-one; (4aR,8aS)-6-[3-[2-[2-(difluoromethyl)phenyl]ethynyl]azetidine-1-carbonyl]-4,4a,5,7,8,8a-hexahydropyrido[4,3-b ][1,4]oxazin-3-one; (4aR,8aS)-6-[3-[2-(2-chloro-6-methylphenyl)ethynyl]azetidine-1-carbonyl]-4,4a,5,7,8,8a-hexahydropyrido[4,3- b][1,4]oxazin-3-one; (4aR,8aS)-6-[3-[2-[2-chloro-6-fluoro-4-(trifluoromethyl)phenyl]ethynyl]azetidine-1-carbonyl]-4,4a,5,7,8,8a -hexahydropyrido[4,3-b][1,4]oxazin-3-one; and (4aR,8aS)-6-(3-((2-chloro-4-(trifluoromethyl)phenyl)ethynyl)azetidine-1-carbonyl)hexahydro-2H-pyrido[4,3-b][1,4]oxazine -3(4H)-she. 40. The method of obtaining compounds of formula (I) according to any one of paragraphs. 1-39, including carrying out the reaction of the first amine of formula 1, where R ¹ is as described in any of paragraphs. 1-39,

with a second amine 2, where A, L, m, n, X and R are as described in any of paragraphs. 1-39,

in the presence of a base and a urea-forming reagent, to form said compound of formula (I). 41. The compound of formula (I) according to any one of paragraphs. 1-39, obtained in accordance with the method according to p. 40. 42. The compound of formula (I) according to any one of paragraphs. 1-39 and 41, characterized in that said compound of formula (I) has an IC ₅₀ with respect to monoacylglycerol lipase below 10 μM, preferably below 5 μM. 43. The compound of formula (I) according to any one of paragraphs. 1-39, 41 and 42 for use as a therapeutically active substance. 44. Pharmaceutical composition containing a compound of formula (I) according to any one of paragraphs. 1-39, 41 and 42 and a therapeutically inert carrier. 45. The use of compounds of formula (I) according to any one of paragraphs. 1-39, 41 and 42 or a pharmaceutical composition according to claim 44 for the treatment or prevention of neuroinflammation, neurodegenerative diseases, pain, cancer and/or mental disorders in a mammal. 46. The use of compounds of formula (I) according to any one of paragraphs. 1-39, 41 and 42 or a pharmaceutical composition according to claim 44 for the treatment or prevention of multiple sclerosis, Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, traumatic brain injury, neurotoxicity, stroke, epilepsy, anxiety, migraine, depression, hepatocellular carcinoma , colon carcinogenesis, ovarian cancer, neuropathic pain, chemotherapy-induced neuropathy, acute pain, chronic pain and/or pain-related spasticity in a mammal. 47. The compound of formula (I) according to any one of paragraphs. 1-39, 41 and 42 or a pharmaceutical composition according to claim 44 for use in the treatment or prevention of neuroinflammation, neurodegenerative diseases, pain, cancer and/or mental disorders in a mammal. 48. The compound of formula (I) according to any one of paragraphs. 1-39, 41 and 42 or a pharmaceutical composition according to claim 44 for use in the treatment or prevention of multiple sclerosis, Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, traumatic brain injury, neurotoxicity, stroke, epilepsy, anxiety, migraine, depression, hepatocellular carcinoma, colon carcinogenesis, ovarian cancer, neuropathic pain, chemotherapy-induced neuropathy, acute pain, chronic pain and/or pain-related spasticity in a mammal. 49. The use of compounds of formula (I) according to any one of paragraphs. 1-39, 41 and 42 for the manufacture of a medicament for the treatment or prevention of neuroinflammation, neurodegenerative diseases, pain, cancer and/or mental disorders in a mammal. 50. The use of compounds of formula (I) according to any one of paragraphs. 1-39, 41 and 42 for the preparation of a medicament for the treatment or prevention of multiple sclerosis, Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, traumatic brain injury, neurotoxicity, stroke, epilepsy, anxiety, migraine, depression, hepatocellular carcinoma, colon carcinogenesis gut, ovarian cancer, neuropathic pain, chemotherapy-induced neuropathy, acute pain, chronic pain and/or pain-related spasticity in a mammal. 51. A method of treating or preventing neuroinflammation, neurodegenerative diseases, pain, cancer and/or mental disorders in a mammal, which includes administering to the mammal an effective amount of a compound of formula (I) according to any one of paragraphs. 1-39, 41 and 42 or the pharmaceutical composition according to claim 44. 52. A method for the treatment or prevention of multiple sclerosis, Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, traumatic brain injury, neurotoxicity, stroke, epilepsy, anxiety, migraine, depression, hepatocellular carcinoma, colon carcinogenesis, ovarian cancer, neuropathic pain induced chemotherapy for neuropathy, acute pain, chronic pain and/or pain-related spasticity in a mammal, said method comprising administering to the mammal an effective amount of a compound of formula (I) according to any one of claims. 1-39, 41 and 42 or the pharmaceutical composition according to claim 44. 53. A method for determining the MAGL inhibitory activity of a test compound, for example, a compound according to any one of paragraphs. 1-39, 41 and 42, which includes measuring the ratio of arachidonic acid/d8-arachidonic acid in solution.