Patent ID: 8853419

Claim:
A process for preparing an L-arginine salt of (R)-2-(7-(4-cyclopentyl-3-(trifluoromethyl)benzyloxy)-1,2,3,4-tetrahydrocyclopenta[b]indol-3-yl)acetic acid of Formula (Ia): comprising the following steps: a) hydrolyzing a compound of Formula (IIk): wherein R 3 is C 1 -C 6 alkyl; in the presence of a lipase and a hydrolyzing-step solvent to form said (R)-2-(7-(4-cyclopentyl-3-(trifluoromethyl)benzyloxy)-1,2,3,4-tetrahydrocyclopenta[b]indol-3-yl)acetic acid of Formula (Ia); and b) contacting said (R)-2-(7-(4-cyclopentyl-3-(trifluoromethyl)benzyloxy)-1,2,3,4-tetrahydrocyclopenta[b]indol-3-yl)acetic acid (Formula (Ia)) with L-arginine or a salt thereof, in the presence of a contacting-step solvent and H 2 O to form said L-arginine salt of (R)-2-(7-(4-cyclopentyl-3-(trifluoromethyl)benzyloxy)-1,2,3,4-tetrahydrocyclopenta[b]indol-3-yl)acetic acid of Formula (Ia).