C[O:2][C:3](=O)[CH2:4][CH2:5][CH2:6][CH2:7][CH2:8][S:9]([C:11]1[CH:16]=[CH:15][C:14]([N:17]([CH3:19])[CH3:18])=[CH:13][CH:12]=1)=[O:10].[NH2:21][OH:22].[OH-].[K+].CO>C1COCC1>[OH:22][NH:21][C:3](=[O:2])[CH2:4][CH2:5][CH2:6][CH2:7][CH2:8][S:9]([C:11]1[CH:16]=[CH:15][C:14]([N:17]([CH3:19])[CH3:18])=[CH:13][CH:12]=1)=[O:10]To a solution of the 6-(4-dimethylamino-benzenesulfinyl)-hexanoic acid methyl ester (1.2 g, 4.0 mmol) in distilled THF (30 mL) containing 50% aqueous hydroxylamine (2.65 mL, 40 mmol) was added at 0° C. a solution of potassium hydroxide in methanol (6.8 mL, 1M, 6.8 mmol) in a dropwise manner. After stirring at 0° C. for 1 h, distilled water (30 mL) was added and the mixture was made neutral by dropwise addition of concentrated hydrochloric acid (10 M) at 0° C. The aqueous solution was extracted with ethyl acetate (3×50 mL) and the combined extracts were washed with brine (100 mL), dried over anhydrous MgSO4, filtered and evaporated to dryness. The solid residue was recrystallised from acetone to give the title compound (728 mg, 61%) as a white powder, mp 95-97° C.
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