Indole derivatives as CRTH2 receptor antagonists

1. A compound of the formula I:

or a pharmaceutically acceptable salt thereof, wherein:

represents either

Y 1 is selected from optionally substituted aryl and —C(R 2 )(R 3 )(R 4 );

Y 2 is selected from H and —C 1-6 alkyl;

Z is selected from H and —C 1-6 alkyl;

R 1a and R 1b are independently selected from H, halogen, —OC 1-6 alkyl, —O-haloC 1-6 alkyl, —C 1-6 alkyl, haloC 1-6 alkyl, optionally substituted aryl and —(C 1-3 alkylene)-optionally substituted aryl;

R 2 is selected from H; —C 1-6 alkyl optionally substituted with halogen, —OH or —NHSO 2 CH 3 ; —OH; —OC 1-6 alkyl; —S(O) n C 1-6 alkyl; —CN; optionally substituted aryl;

optionally substituted —O-aryl and optionally substituted heteroaryl, wherein n is 0, 1 or 2;

R 3 is selected from H, —C 1-6 alkyl, C 1-6 haloalkyl, optionally substituted aryl and optionally substituted heteroaryl; and

R 4 is selected from H, —C 1-6 alkyl, C 1-6 haloalkyl, optionally substituted aryl and optionally substituted heteroaryl; or

R 3 , R 4 and the carbon atom to which they are attached together form —C 3-6 cycloalkyl, fluorenyl or —C 3-6 heterocyclyl having a ring heteroatom selected from —N(R a )—, —O— and —S—; or

R 3 , R 4 together represent C 1-6 alkylidene;

R a is H, C 1-6 alkyl or —C(O)C 1-6 alkyl; and

the optional substituent for aryl and heteroaryl is 1 to 4 groups independently selected from halogen, —C 1-3 alkoxy, —C 1-3 haloalkyl, hydroxy-C 1-3 alkyl, —S(O)n-C 1-3 alkyl, amino, and mono- and di-(C 1-3 alkyl)amino.

2. The compound of claim 1 or a pharmaceutically acceptable salt thereof wherein R 1b , Y 2 , and Z are each H.

3. The compound of claim 1 having the formula Ia or a pharmaceutically acceptable salt thereof:

wherein Y 1 and R 1a are as defined in claim 1 .

4. The compound of claim 1 having the formula Ib or a pharmaceutically acceptable salt thereof:

wherein Y 1 and R 1a are as defined in claim 1 .

5. The compound of claim 3 or a pharmaceutically acceptable salt thereof wherein Y 1 is —C(R 3 )(R 4 )-optionally substituted phenyl or —CH 2 O-optionally substituted phenyl; and (i) one of R 3 and R 4 is H, and the other is H, —C 1-3 alkyl or optionally substituted phenyl; or (ii) R 3 , R 4 and the carbon atom to which they are attached together form —C 3-6 cycloalkyl; or (iii) R 3 and R 4 together represent —C 1-3 alkylidene.

6. The compound of claim 5 or a pharmaceutically acceptable salt thereof wherein Y 1 is —C(R 3 )(R 4 )-phenyl optionally substituted with 1 or 2 halogen atoms.

7. The compound of claim 6 or a pharmaceutically acceptable salt thereof wherein one of R 3 and R 4 is H, and the other is H, —C 1-3 alkyl or phenyl optionally substituted with 1 or 2 halogen atoms.

8. The compound of claim 6 or a pharmaceutically acceptable salt thereof wherein R 3 , R 4 and the carbon atom to which they are attached together form —C 3-6 cycloalkyl.

9. The compound of claim 6 or a pharmaceutically acceptable salt thereof wherein R 3 and R 4 together represent —C 1-3 alkylidene.

10. A compound selected from the group consisting of:

[7-(4-benzyl-[1,2,3]triazol-1-yl)-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl]-acetic acid;

{7-[4-(4-methoxy-phenyl)[1,2,3]triazol-1-yl]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}-acetic acid;

[7-(5-benzyl-[1,2,3]triazol-1-yl)-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl]-acetic acid;

(7-{5-[(2,6-dichlorophenoxy)methyl]-1H-1,2,3-triazol-1-yl}-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl)acetic acid;

(7-{5-[1-(4-fluoro-phenyl)-1-hydroxy-ethyl]-[1,2,3]triazol-1-yl}-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl)-acetic acid;

{7-[5-(1-phenyl-cyclopentyl)-[1,2,3]triazol-1-yl]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}-acetic acid;

[7-(5-benzyl-[1,2,3]triazol-1-yl)-4-fluoro-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl]-acetic acid;

{4-fluoro-7-[5-(4-fluorobenzyl)-1H-[1,2,3]triazol-1-yl]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}-acetic acid;

{(7R)-4-fluoro-7-[5-(4-fluorobenzyl)-1H-[1,2,3]triazol-1-yl]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}-acetic acid;

[3-(5-benzyl-[1,2,3]triazol-1-yl)-1,2,3,4-tetrahydro-carbazol-9-yl]-acetic acid;

{7-[4-(4-fluoro-phenyl)-[1,2,3]triazol-1-yl]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}-acetic acid;

{7-[4-(4-methanesulfonylamino-butyl)-[1,2,3]triazol-1-yl]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}-acetic acid;

{7-[4-(1-hydroxy-2-methyl-propyl)-[1,2,3]triazol-1-yl]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}-acetic acid;

{7-[4-(1-hydroxy-1-phenyl-ethyl)-[1,2,3]triazol-1-yl]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}-acetic acid;

[7-(4-phenoxymethyl-[1,2,3]triazol-1-yl)-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl]-acetic acid;

{7-[4-(4-methanesulfonyl-phenyl)-[1,2,3]triazol-1-yl]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}-acetic acid;

(7-{4-[4-(1-hydroxy-1-methyl-ethyl)-phenyl]-[1,2,3]triazol-1-yl}-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl)-acetic acid;

{7-[4-(4-trifluoromethyl-phenyl)-[1,2,3]triazol-1-yl]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}acetic acid;

[7-(4-naphthalen-1-yl-[1,2,3]triazol-1-yl)-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl]-acetic acid;

{7-[4-(4-dimethylamino-phenyl)-[1,2,3]triazol-1-yl]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}-acetic acid;

{7-[5-(4-fluoro-phenyl)-[1,2,3]triazol-1-yl]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}-acetic acid;

[7-(5-phenoxymethyl-[1,2,3]triazol-1-yl)-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl]-acetic acid;

(7-{5-[(4-bromophenyl)-hydroxy-methyl]-[1,2,3]triazol-1-yl}-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl)-acetic acid;

4-[3-(10-carboxymethyl-6,7,8,9-tetrahydropyrido[1,2-a]indol-7-yl)-3H-[1,2,3]triazol-4-yl]-piperidine-1-carboxylic acid tert-butyl ester;

[7-(5-cyclohexyl-[1,2,3]triazol-1-yl)-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl]-acetic acid;

{7-[5-(9-hydroxy-9H-fluoren-9-yl)-[1,2,3]triazol-1-yl]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}-acetic acid;

(7-{5-[1-(4-fluorophenyl)-vinyl]-[1,2,3]triazol-1-yl}-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl)-acetic acid;

(7-{(R)-5-[bis-(4-fluorophenyl)-hydroxy-methyl]-[1,2,3]triazol-1-yl}-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl)-acetic acid;

{(R)-7-[5-(4-fluorobenzyl)-[1,2,3]triazol-1-yl]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}-acetic acid;

{(R)-7-[5-(1-phenylethyl)-[1,2,3]triazol-1-yl]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}-acetic acid;

((R)-7-{5-[bis-(4-fluorophenyl)-methyl]-[1,2,3]triazol-1-yl}-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl)-acetic acid;

((R)-7-{5-[1-(4-fluorophenyl)-1-hydroxyethyl]-[1,2,3]triazol-1-yl}-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl)-acetic acid;

{4-fluoro-7-[5-(1-phenyl-ethyl)-[1,2,3]triazol-1-yl]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}-acetic acid;

{7-[5-(3,4-difluorobenzyl)-1H-1,2,3-triazol-1-yl]-4-fluoro-6,7,8,9-tetrahydropyrido[1,2-a]-indol-10-yl}acetic acid;

{7-[5-(4-chlorobenzyl)-1H-1,2,3-triazol-1-yl]-4-fluoro-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}acetic acid; and

{7-[5-(2,2,2-trifluoro-1-hydroxy-1-phenylethyl)-1H-1,2,3-triazol-1-yl]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}acetic acid;

or a pharmaceutically acceptable salt thereof.

11. A compound selected from the group consisting of:

[7-(5-benzyl-[1,2,3]triazol-1-yl)-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl]-acetic acid;

(7-{5-[1-(4-fluorophenyl)-1-hydroxy-ethyl]-[1,2,3]triazol-1-yl}-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl)-acetic acid;

{7-[5-(1-phenyl-cyclopentyl)-[1,2,3]triazol-1-yl]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}-acetic acid;

[7-(5-benzyl-[1,2,3]triazol-1-yl)-4-fluoro-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl]-acetic acid;

{4-fluoro-7-[5-(4-fluoro-benzyl)-[1,2,3]triazol-1-yl]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}-acetic acid;

{(7R)-4-fluoro-7-[5-(4-fluorobenzyl)-1H-[1,2,3]triazol-1-yl]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}-acetic acid;

(7-{5-[1-(4-fluorophenyl)-vinyl]-[1,2,3]triazol-1-yl}-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl)-acetic acid;

(7-{(R)-5-[bis-(4-fluorophenyl)-hydroxy-methyl]-[1,2,3]triazol-1-yl}-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl)-acetic acid;

{(R)-7-[5-(4-fluorobenzyl)-[1,2,3]triazol-1-yl]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}-acetic acid;

{(R)-7-[5-(1-phenylethyl)-[1,2,3]triazol-1-yl]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}-acetic acid;

((R)-7-{5-[Bis-(4-fluorophenyl)-methyl]-[1,2,3]triazol-1-yl}-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl)-acetic acid;

((R)-7-{5-[1-(4-fluorophenyl)-1-hydroxyethyl]-[1,2,3]triazol-1-yl}-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl)-acetic acid; and

{4-fluoro-7-[5-(1-phenylethyl)-[1,2,3]triazol-1-yl]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}-acetic acid;

or a pharmaceutically salt thereof.

12. A pharmaceutical composition comprising a therapeutically effective amount of the compound of claim 1 or a pharmaceutically acceptable salt thereof and a pharmaceutically acceptable carrier.

13. The pharmaceutical composition of claim 12 or a pharmaceutically acceptable salt thereof further comprising a leukotriene receptor antagonist.

14. The pharmaceutical composition of claim 13 wherein said leukotriene receptor antagonist is selected from the group consisting of montelukast, pranlukast and zafirlukast and pharmaceutically acceptable salts of each.

15. A method of treating asthma comprising administering to a mammalian patient in need thereof the compound of claim 1 or a pharmaceutically acceptable salt thereof in an amount effective for treating asthma.

16. The compound of claim 1 or a pharmaceutically acceptable salt thereof, wherein the compound is {4-fluoro-7-[5-(4-fluorobenzyl)-1H-[1,2,3]triazol-1-yl]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}-acetic acid.

17. A compound, {(7R)-4-fluoro-7-[5-(4-fluorobenzyl)-1H-[1,2,3]triazol-1-yl]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}-acetic acid or a pharmaceutically acceptable salt thereof.

18. A compound, {(7R)-4-fluoro-7-[5-(4-fluorobenzyl)-1H-[1,2,3]triazol-1-yl]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}-acetic acid.

19. A pharmaceutical composition comprising a therapeutically effective amount of the compound of claim 17 or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable carrier.

20. The pharmaceutical composition of claim 14 , wherein the leukotriene receptor antagonist is montelukast or a pharmaceutically acceptable salt thereof.

21. The pharmaceutical composition of claim 19 , further comprising montelukast or a pharmaceutically acceptable salt thereof.

22. The method of claim 15 , wherein said asthma is allergic asthma.