In a stream of nitrogen and at 0° C., 0.12 ml (1.30 mmol) of acetic anhydride was added to an anhydrous tetrahydrofuran (10 ml) solution containing 500 mg (1.20 mmol) of 3-(4-chlorobenzyloxy)-N-(2-sulfamoylphenyl)benzamide produced in Reference Example 4 and 293 mg (2.40 mmol) of 4-dimethylaminopyridine, the mixture was stirred at room temperature for 1 hour and then the solvent was evaporated under a reduced pressure. The resulting residue was dissolved in ethyl acetate, washed with water, a potassium hydrgensulfate aqueous solution and saturated brine in that order and dried over anhydrous sodium sulfate, and then the solvent was evaporated under a reduced pressure. The resulting residue was recrystallized from an ethyl acetate-diethyl ether mixed solvent to obtain 290 mg (yield: 52.7%) of the title compound.
