C([O:3][C:4](=[O:18])[C:5]1[CH:10]=[CH:9][CH:8]=[C:7]([NH:11][S:12]([CH2:15][CH2:16][CH3:17])(=[O:14])=[O:13])[CH:6]=1)C.[OH-].[Li+].O1CCCC1.Cl>O>[CH2:15]([S:12]([NH:11][C:7]1[CH:6]=[C:5]([CH:10]=[CH:9][CH:8]=1)[C:4]([OH:18])=[O:3])(=[O:13])=[O:14])[CH2:16][CH3:17]To 3-(propane-1-sulfonylamino)-benzoic acid ethyl ester (75, 1.60 g, 5.90 mmol) in water was added lithium hydroxide (1.0 g, 4.2 mmol) and tetrahydrofuran (20 mL). The reaction was stirred at room temperature overnight. The reaction mixture was acidified with 1 N HCl, and extracted with ethyl acetate. The organic layer was dried over anhydrous sodium sulfate and filtered. The filtrate was concentrated and washed with ethyl acetate to give the compound (76, 1.2 g, 84.5%) as white solid. MS (ESI) [M−H+]+=242.1.
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