C[O:2][C:3](=[O:22])[CH:4]([C:11]1[CH:16]=[CH:15][C:14]([S:17]([CH3:20])(=[O:19])=[O:18])=[C:13]([F:21])[CH:12]=1)[CH2:5][CH:6]1[CH2:10][CH2:9][CH2:8][CH2:7]1.[OH-].[Li+].O.Cl>O1CCCC1.C(OCC)(=O)C>[CH:6]1([CH2:5][CH:4]([C:11]2[CH:16]=[CH:15][C:14]([S:17]([CH3:20])(=[O:19])=[O:18])=[C:13]([F:21])[CH:12]=2)[C:3]([OH:22])=[O:2])[CH2:10][CH2:9][CH2:8][CH2:7]1
A solution of 3-cyclopentyl-2-(3-fluoro-4-methanesulfonyl-phenyl)-propionic acid methyl ester (110 mg, 0.335 mmol) in tetrahydrofuran (1 mL) was treated with a 0.8M aqueous lithium hydroxide solution (630 μL, 0.502 mmol). The reaction mixture was stirred at 25° C. for 2 h and then treated with water (30 mL), a 1N aqueous hydrochloric acid solution (2 mL), and ethyl acetate (30 mL). The layers were separated, and the resulting aqueous layer was back-extracted with ethyl acetate (30 mL). The combined organic layers were dried over magnesium sulfate, filtered, and concentrated in vacuo to afford 3-cyclopentyl-2-(3-fluoro-4-methanesulfonyl-phenyl)-propionic acid as a pale yellow oil which solidified to a pale yellow solid upon sitting at 25° C. The pale yellow solid corresponding to 3-cyclopentyl-2-(3-fluoro-4-methanesulfonyl-phenyl)-propionic acid (106 mg, 98%) was used without further purification: mp 115-117° C.; EI-HRMS m/e calcd for C15H19FO4S (M+) 314.0988, found 314.0986.
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