C([O:3][C:4](=[O:23])[CH:5]([C:12]1[CH:17]=[CH:16][C:15]([S:18]([CH2:21][CH3:22])(=[O:20])=[O:19])=[CH:14][CH:13]=1)[CH2:6][CH:7]1[CH2:11][CH2:10][CH2:9][CH2:8]1)C.[OH-].[Li+]>O1CCCC1>[CH:7]1([CH2:6][CH:5]([C:12]2[CH:17]=[CH:16][C:15]([S:18]([CH2:21][CH3:22])(=[O:20])=[O:19])=[CH:14][CH:13]=2)[C:4]([OH:23])=[O:3])[CH2:11][CH2:10][CH2:9][CH2:8]1A solution of 3-cyclopentyl-2-(4-ethanesulfonyl-phenyl)-propionic acid ethyl ester (2.50 g, 7.39 mmol) in tetrahydrofuran (30 mL) was treated with a 0.8M aqueous lithium hydroxide solution (11.1 mL, 8.86 mmol). The reaction mixture was stirred at 25° C. for 23 h. The resulting reaction mixture was partitioned between water (75 mL) and ethyl acetate (75 mL) and then treated with a 1N aqueous hydrochloric acid solution (15 mL). The layers were shaken and separated. The organic layer was dried over magnesium sulfate, filtered, and concentrated in vacuo to afford 3-cyclopentyl-2-(4-ethanesulfonyl-phenyl)-propionic acid (2.20 g, 96%) as a white solid which was used without further purification: mp 137-138° C.; FAB-HRMS m/e calcd for C16H22O4S (M+H)+ 311.1317, found 311.1321.
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