Purine compounds

1. A compound of the formula:

wherein;

R 1 is selected from H, F, Cl, C 1 -C 2 alkyl, CF 3 , cyclopropyl, OCH 3 , OCF 3 and CN;

R 2 is selected from tetrahydrofuranyl, tetrahydropyranyl, azetidinyl-1-carboxylic acid methyl ester and tetrahydrothiophenyl-1,1-dioxide;

R 3 is H or combines with R 4 together with the atoms to which they are attached to form a fused pyrrolidin-2-one;

R 4 is selected from C 1 -C 2 alkyl, C 1 -C 2 fluoroalkyl, cyclopropyl and COCH 3 ;

R 5 is selected from H, CH 3 and CF 3 ;

n is 0 or 1;

X 1 and X 3 are independently selected from N, CH and CR 6 ;

X 2 is selected from CH and CR 6 ;

with the proviso that only one of X 1 , X 2 and X 3 may be other than CH;

R 6 is selected from F, Cl, CF 3 , OCH 3 and OCF 3 ;

or a pharmaceutically acceptable salt thereof.

2. A compound according to claim 1 , or a pharmaceutically acceptable salt thereof, wherein R 1 is selected from Cl, C 1 -C 2 alkyl, CF 3 , cyclopropyl and OCF 3 .

3. A compound according to claim 1 , or a pharmaceutically acceptable salt thereof, wherein R 1 is Cl.

4. A compound according to claim 2 , or a pharmaceutically acceptable salt thereof, wherein R 2 is selected from tetrahydrofuranyl and tetrahydropyranyl.

5. A compound according to claim 4 , or a pharmaceutically acceptable salt thereof, wherein n is 0.

6. A compound according to claim 2 , or a pharmaceutically acceptable salt thereof, wherein R 4 is selected from C 1 -C 2 alkyl, C 1 -C 2 fluoroalkyl or cyclopropyl.

7. A compound according to claim 2 , or a pharmaceutically acceptable salt thereof, wherein R 4 is C 1 -C 2 alky.

8. A compound according to claim 7 , or a pharmaceutically acceptable salt thereof, wherein R 3 is H.

9. A compound according to claim 2 , or a pharmaceutically acceptable salt thereof, wherein R 5 is CH 3 .

10. A compound according to claim 2 , or a pharmaceutically acceptable salt thereof, wherein X 1 , X 2 and X 3 are independently selected from CH and CR 6 where R 6 is selected from Cl, CF 3 , OCH 3 and OCF 3 .

11. A compound according to claim 2 , or a pharmaceutically acceptable salt thereof, wherein X 1 , X 2 and X 3 are each CH.

12. A compound according to claim 1 selected from 8-(2-Chloro-pyridin-3-yl)-2-methyl-6-(4-methyl-piperazin-1-yl)-9-(R)-tetrahydro-furan-3-yl-9H-purine; 2-Methyl-6-(4-methyl-piperazin-1-yl)-9-(tetrahydro-pyran-4-yl)-8-(2-trifluoromethyl-phenyl)-9H-purine; 2-Methyl-6-(4-methyl-piperazin-1-yl)-9-(R)-tetrahydro-furan-3-yl-8-(2-trifluoromethyl-phenyl)-9H-purine; 2-Methyl-6-(4-methyl-piperazin-1-yl)-9-(R)-tetrahydro-furan-3-yl-8-o-tolyl-9H-purine; 8-(2-Chloro-phenyl)-2-methyl-6-(4-methyl-piperazin-1-yl)-9-(S)-tetrahydro-furan-3-yl-9H-purine; 8-(2-Chloro-phenyl)-2-methyl-6-(4-methyl-piperazin-1-yl)-9-(R)-tetrahydro-furan-3-yl-9H-purine; 8-(2-Chloro-phenyl)-2-methyl-6-(4-methyl-piperazin-1-yl)-9-(tetrahydro-pyran-4-yl)-9H-purine; and 8-(2-Chloro-phenyl)-6-(4-ethyl-piperazin-1-yl)-2-methyl-9-(tetrahydro-pyran-4-ylmethyl)-9H-purine; or a pharmaceutically acceptable salt thereof.

13. A compound according to claim 1 being 8-(2-Chloro-phenyl)-2-methyl-6-(4-methyl-piperazin-1-yl)-9-(tetrahydro-pyran-4-yl)-9H-purine; or a pharmaceutically acceptable salt thereof.

14. A pharmaceutical composition comprising a compound of the formula:

wherein;

R 1 is selected from H, F, Cl, C 1 -C 2 alkyl, CF 3 , cyclopropyl, OCH 3 , OCF 3 and CN;

R 2 is selected from tetrahydrofuranyl, tetrahydropyranyl, azetidinyl-1-carboxylic acid methyl ester and tetrahydrothiophenyl-1,1-dioxide;

R 3 is H or combines with R 4 together with the atoms to which they are attached to form a fused pyrrolidin-2-one;

R 4 is selected from C 1 -C 2 alkyl, C 1 -C 2 fluoroalkyl, cyclopropyl and COCH 3 ;

R 5 is selected from H, CH 3 and CF 3 ;

n is 0 or 1;

X 1 and X 3 are independently selected from N, CH and CR 6 ;

X 2 is selected from CH and CR 6 ;

with the proviso that only one of X 1 , X 2 and X 3 may be other than CH;

R 6 is selected from F, Cl, CF 3 , OCH 3 and OCF 31

or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable diluent or carrier.

15. A method for the treatment of pain, which comprises administering an effective amount of a compound of the formula:

wherein;

R 1 is selected from H, F, Cl, C 1 -C 2 alkyl, CF 3 , cyclopropyl, OCH 3 OCF 3 and CN;

R 2 is selected from tetrahydrofuranyl, tetrahydropyranyl, azetidinyl-1-carboxylic acid methyl ester and tetrahydrothiophenyl-1,1-dioxide;

R 3 is H or combines with R 4 together with the atoms to which they are attached to form a fused pyrrolidin-2-one;

R 4 is selected from C 1 -C 2 alkyl, C 1 -C 2 fluoroalkyl, cyclopropyl and COCH 3 ;

R 5 is selected from H, CH 3 and CF 3 ;

n is 0 or 1;

X 1 and X 3 are independently selected from N, CH and CR 6 ;

X 2 is selected from CH and CR 6 ;

with the proviso that only one of X 1 , X 2 and X 3 may be other than CH;

R 6 is selected from F, Cl, CF 3 , OCH 3 and OCF 3 ;

or a pharmaceutically acceptable salt thereof, to a human being or animal in need thereof.

16. A method according to claim 15 for the treatment of osteoarthritic pain.

17. The pharmaceutical composition according to claim 14 where the compound is 8 (2 Chloro-phenyl)-2-methyl-6-(4-methyl-piperazin-1-yl)-9-(tetrahydro-pyran-4-yl)-9H-purine, or a pharmaceutically acceptable salt thereof.

18. The method according to claim 15 where the compound is 8-(2-Chloro-phenyl)-2-methyl-6-(4-methyl-piperazin-1-yl)-9-(tetrahydro-pyran-4-yl)-9H-purine, or a pharmaceutically acceptable salt thereof.

19. The method according to claim 18 , wherein the pain is osteoarthritic pain.