C[O:2][C:3](=[O:24])[CH:4]([C:11]1[CH:16]=[CH:15][C:14]([S:17]([C:20]([F:23])([F:22])[F:21])(=[O:19])=[O:18])=[CH:13][CH:12]=1)[CH2:5][CH:6]1[CH2:10][CH2:9][CH2:8][CH2:7]1.[OH-].[Li+]>O1CCCC1>[CH:6]1([CH2:5][CH:4]([C:11]2[CH:12]=[CH:13][C:14]([S:17]([C:20]([F:23])([F:21])[F:22])(=[O:19])=[O:18])=[CH:15][CH:16]=2)[C:3]([OH:24])=[O:2])[CH2:10][CH2:9][CH2:8][CH2:7]1A solution of 3-cyclopentyl-2-(4-trifluoromethanesulfonyl-phenyl)propionic acid methyl ester (708.2 mg, 1.94 mmol) in tetrahydrofuran (2.4 mL) was treated with a 0.8M aqueous lithium hydroxide solution (3.6 mL, 2.92 mmol). The reaction mixture was stirred at 25° C. for 23 h and then concentrated in vacuo to remove tetrahydrofuran. The remaining aqueous layer was acidified to pH=2 with a 10% aqueous hydrochloric acid solution and then extracted with ethyl acetate (2×100 mL). The combined organic layers were washed with a saturated aqueous sodium chloride solution (1×100 mL), dried over sodium sulfate, filtered, and concentrated in vacuo to afford a cream solid. This solid was purified by triturating with diethyl ether/petroleum ether to provide pure 3-cyclopentyl-2-(4-trifluoromethanesulfonyl-phenyl)propionic acid (527.0 mg, 77%) as a white solid: mp 143-145° C.; EI-HRMS m/e calcd for C15H17F3O4S (M+) 350.0800, found 350.0816.
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