[C:1]([NH:4][CH2:5][C:6]1[CH:14]=[CH:13][C:9]([C:10]([OH:12])=[O:11])=[CH:8][CH:7]=1)(=[O:3])[CH3:2].Cl.[CH3:16]O>>[C:1]([NH:4][CH2:5][C:6]1[CH:14]=[CH:13][C:9]([C:10]([O:12][CH3:16])=[O:11])=[CH:8][CH:7]=1)(=[O:3])[CH3:2]4-Acetamidomethylbenzoic acid(4.0 g) was dissolved in 0.5% hydrochloric acid—methanol solution (100 ml). The mixture was stirred at 40° C. for 3.5 hr, and poured into ice water (300 ml) and extracted with ethyl acetate (100 ml×4). The extract was washed with saturated sodium hydrogencarbonate solution and saturated brine, and dried over anhydrous sodium sulfate. The solvent was evaporated to give a pale-yellow solid (4.3 g). The obtained solid was crystallized from ethyl acetate (50 ml) to give the title compound (3.2 g) as pale-yellow white crystals, m.p.=110-111° C.
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