[CH:1]1([O:6][C:7]2[CH:8]=[C:9]([CH:14]=[CH:15][C:16]=2[S:17][CH3:18])[C:10]([O:12]C)=[O:11])[CH2:5][CH2:4][CH2:3][CH2:2]1.C(=O)([O-])[O-].[K+].[K+]>CO.O>[CH:1]1([O:6][C:7]2[CH:8]=[C:9]([CH:14]=[CH:15][C:16]=2[S:17][CH3:18])[C:10]([OH:12])=[O:11])[CH2:2][CH2:3][CH2:4][CH2:5]1A suspension of methyl 3-cyclopentyloxy-4-(methylthio)benzoate (0.8 g) in methanol (10 mL) and water (5 mL) is treated with potassium carbonate (0.48 g) and the mixture is heated at reflux for 7 hours. The mixture is concentrated, and the resulting residue is partitioned between diethyl ether (20 mL) and water (20 mL). The aqueous layer is separated, acidified to pH 1 by treatment with dilute hydrochloric acid (2 N), and extracted with dichloromethane (2×25 mL). The combined organic extracts are dried and concentrated, to give 3-cyclopentyloxy-4-(methylthio)benzoic acid (0.7 g) in the form of a white solid m.p. 150°-152° C.
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