Indole derivatives as CRTH2 receptor antagonists

1. A compound of the formula Ib:

and pharmaceutically acceptable salts thereof, wherein:

Y is methylene;

R 1 is selected from H, halogen, —OC 1-6 alkyl, and —C 1-6 alkyl;

R 2 is selected from H, halogen, —C 1-6 alkyl, —OC 1-6 alkyl, —SC 1-6 alkyl, —S(O)C 1-6 alkyl, —S(O) 2 C 1-6 alkyl, —CN, aryl and heteroaryl;

R 3 is selected from H, C 1-6 alkyl and benzyl optionally substituted on the phenyl portion with 1 to 3 halogen;

R c is selected from halogen, NR f R g , SO 2 NR f R g , CN, C 1-6 alkoxy, C 1-6 alkyl, haloC 1-6 alkoxy, and haloC 1-6 alkyl;

R d and R e are independently selected from hydrogen, C 1-6 alkyl, —C 1-6 alkyl-C 3-6 cycloalkyl, hydroxy, C 1-6 alkoxy, aryl optionally substituted with 1 to 3 groups independently selected from R c , and NR f R g ; or

R d , R e together with the carbon atom to which they are both attached form a C 3-6 cycloalkyl optionally having a ring heteroatom selected from —O—, —S—, —N(C(O)R f )— and —N(R f )—, and optionally substituted with 1 to 3 C 1-3 alkyl groups;

R f and R g are independently selected from hydrogen and C 1-3 alkyl; or

R f , R g together with the atom to which they are both attached form a 3- to 6-membered ring.

2. The compound of claim 1 wherein R d , R e and the carbon to which they are both attached together form a C 3-6 cycloalkyl optionally substituted with one or two C 1-3 alkyl groups.

3. The compound of claim 1 selected from the group consisting of:

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

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

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

[(7R)-7-({[1-(4-fluorophenyl)cyclopentyl]carbonyl}amino)-6,7,8,9-tetrahydropyrido[1,2-a]-indol-10-yl]acetic acid;

{(7R)-7-[{[1-(4-fluorophenyl)cyclopentyl]carbonyl}(methyl)amino]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}acetic acid;

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

{(7R)-7-[[(2,4-difluorophenyl)acetyl](methyl)amino]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}acetic acid;

{(7R)-7-[[(2-chloro-4-fluorophenyl)acetyl](methyl)amino]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}acetic acid;

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

{(7R)-7-[{[4-fluoro-2-(trifluoromethyl)phenyl]acetyl}(methyl)amino]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}acetic acid;

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

{(7R)-7-[[(2-(2-bromo-4-fluorophenyl)propanoyl](methyl)amino]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}acetic acid;

(7R)-7-[[(4-chlorophenyl)acetyl](methyl)amino]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}acetic acid;

{(7R)-7-[{[1-(4-chlorophenyl)cyclopentyl]carbonyl}(methyl)amino]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}acetic acid;

{(7R)-7-[[(4-methoxyphenyl)acetyl](methyl)amino]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}acetic acid;

{(7R)-7-[methyl(phenylacetyl)amino]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}acetic acid;

{(7R) -7-[[(3,4-difluorophenyl)acetyl](methyl)amino]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}acetic acid;

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

((7R)-7-{methyl[2-phenylpropanoyl]amino}-6,7,8,9-tetrahydropyrido[1,2-c]indol1-10-yl)-acetic acid;

{(7R)-7-[{[1-(4-fluorophenyl)cyclopropyl]carbonyl}(methyl)amino]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}acetic acid;

{(7R)-7-[{[1-(4-fluorophenyl)cyclobutyl]carbonyl}(methyl)amino]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}acetic acid;

{(7R)-7-[[2-(4-fluorophenyl)-2-piperidin-1-ylacetyl](methyl)amino]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}acetic acid;

{(7R)-7-[[(2-bromo-4-fluorophenyl)acetyl](methyl)amino]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}acetic acid;

{(7R)-7-[{[1-(4-fluorophenyl)-2,2-dimethylcyclopropyl]carbonyl}(methyl)amino]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}acetic acid;

{(7R)-7-[[-2-methoxy-2-phenylacetyl](methyl)amino]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}acetic acid;

((7R)-7-{[2,2-bis-(4-fluoro-phenyl)-acetyl]-methyl-amino}-6,7,8,9-tetrahydro-pyrido[1,2-a]indol-10-yl)-acetic acid;

{(7R)-7-[(diphenylacetyl)(methyl)amino]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}acetic acid;

{(7R)-7-[(diphenylacetyl)(methyl)amino]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}acetic acid;

((7R)-7-{[3-cyclopropyl-2-(4-fluoro-phenyl)-propionyl]-methyl-amino}-6,7,8,9-tetrahydro-pyrido[1,2-a]indol-10-yl)-acetic acid;

[(7R)-7-{[(2R)-2-hydroxy-2-phenylpropanoyl](methyl)amino}-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl]acetic acid;

[(7R)-7-{[(2S)-2-hydroxy-2-phenylpropanoyl](methyl)amino}-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl]acetic acid;

((7R)-7-{ethyl-[1-(4-fluoro-phenyl)-cyclopropanecarbonyl]-amino}-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl)-acetic acid

((7R)-7-{[4-(4-fluoro-phenyl)-tetrahydro-pyran-4-carbonyl]-methyl-amino}-6,7,8,9-tetrahydro-pyrido[1,2-a]indol-10-yl)-acetic acid;

{(7R)-7-[(2-methoxy-2-phenyl-acetyl)-methyl-amino]-6,7,8,9-tetrahydro-pyrido[1,2-a]indol-10-yl}-acetic acid;

[(7R)-7-{methyl[(2R or 2S)-2-phenylpropanoyl]amino}-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl]acetic acid;

((7R)-7-{[2-(4-dimethylamino-phenyl)-acetyl]-methyl-amino}-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl)-acetic acid; and

((7R)-4-fluoro-7-{[(2R or 2S)-2-(4-fluorophenyl)-propionyl]-methyl-amino}-6,7,8,9-tetrahydro-pyrido[1,2-a]indol-10-yl)-acetic acid,

or a pharmaceutically acceptable salt thereof.

4. The compound of claim 1 selected from the group consisting of:

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

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

{(7R)-7-[{[1-(4-fluorophenyl)cyclopentyl]carbonyl}(methyl)amino]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}acetic acid;

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

{(7R)-7-[{[1-(4-chlorophenyl)cyclopentyl]carbonyl}(methyl)amino]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}acetic acid;

((7R)-7-{methyl[2-phenylpropanoyl]amino}-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl) -acetic acid;

{(7R)-7-[{[1-(4-fluorophenyl)cyclopropyl]carbonyl}(methyl)amino]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}acetic acid;

{(7R)-7-[{[1-(4-fluorophenyl)cyclobutyl]carbonyl}(methyl)amino]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}acetic acid; and

{(7R)-7-[{[1-(4-fluorophenyl)-2,2-dimethylcyclopropyl]carbonyl}(methyl)amino]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}acetic acid,

or a pharmaceutically acceptable salt thereof.

5. 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.

6. The compound of claim 1 or a pharmaceutically acceptable salt thereof, wherein the compound is {(7R)-7-[[2-(4-fluorophenyl)propanoyl](methyl)amino]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}acetic acid.

7. The compound of claim 1 or a pharmaceutically acceptable salt thereof, wherein the compound is ((7R)-7-{(4-fluorobenzyl)[(4-fluorophenyl)acetyl]amino}-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl)acetic acid.

8. The compound of claim 1 or a pharmaceutically acceptable salt thereof, wherein the compound is {(7R)-7-[{[1-(4-fluorophenyl)cyclopentyl]carbonyl}(methyl)amino]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}acetic acid.

9. The compound of claim 1 or a pharmaceutically acceptable salt thereof, wherein the compound is {(7R)-7-[{[1(4-fluorophenyl)-2,2-dimethylcyclopropyl]carbonyl}(methyl)amino]-6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl}acetic acid.

10. The compound of claim 1 or a pharmaceutically acceptable salt thereof, wherein the compound is ((7R)-4-fluoro-7-{[(2R or 2S)-2-(4-fluorophenyl)-propionyl]-methyl-amino}-6,7,8,9-tetrahydro-pyrido[1,2-a]indol-10-yl)-acetic acid.