[CH3:1][O:2][C:3](=[O:24])[CH:4]([C:11]1[CH:16]=[CH:15][C:14]([S:17]([CH3:20])(=[O:19])=[O:18])=[C:13]([N+:21]([O-])=O)[CH:12]=1)[CH2:5][CH:6]1[CH2:10][CH2:9][CH2:8][CH2:7]1.[Cl-].[NH4+]>CO.O.[Zn]>[CH3:1][O:2][C:3](=[O:24])[CH:4]([C:11]1[CH:16]=[CH:15][C:14]([S:17]([CH3:20])(=[O:18])=[O:19])=[C:13]([NH2:21])[CH:12]=1)[CH2:5][CH:6]1[CH2:7][CH2:8][CH2:9][CH2:10]1A solution of 3-cyclopentyl-2-(4-methanesulfonyl-3-nitrophenyl)-propionic acid methyl ester (1.50 g, 4.22 mmol) in methanol (30 mL) was treated with a solution of ammonium chloride (474 mg, 8.86 mmol) in water (3 mL). The reaction mixture was stirred at 25° C. for 5 min and then treated with zinc dust (2.70 g, 41.36 mmol). The reaction mixture was heated under reflux for 2 h. The reaction mixture was allowed to cool to 25° C. and then filtered through a pad of celite. The filtrate was concentrated in vacuo. The resulting orange oil was dissolved in ethyl acetate, dried over magnesium sulfate, filtrated, and concentrated in vacuo. Flash chromatography (Merck Silica gel 60, 230-400 mesh, 2/1 hexanes/ethyl acetate) afforded 2-(3-amino-4-methanesulfonyl-phenyl)-3-cyclopentyl-propionic acid methyl ester (1.49 g, 98%) as a white solid: mp 98-100° C.; EI-HRMS m/e calcd for C16H23NO4S (M+) 325.1348, found 325.1358.
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