To a solution of the ethyl[[[5-chloro-4-[(4-chlorophenylsulfonyl)(2,5-difluorophenyl)methyl]pyridin-2-yl]amino]sulfonyl]acetate (60 mg, 0.104 mmol) obtained in Example 283 in a mixture of tetrahydrofuran (5 ml) and water (1 ml) was added lithium hydroxide monohydrate (9.1 mg, 0.218 mmol). The resulting mixture was stirred at room temperature for 2 hours. To the reaction mixture was added 1N hydrochloric acid. The resulting mixture was extracted with methylene chloride. The extract was dried over anhydrous sodium sulfate, and filtered. The filtrate was concentrated under reduced pressure. The residue thus obtained was subjected to silica gel column chromatography. The fraction obtained from the methanol:methylene chloride (=1:30) eluate containing 0.5% trifluoroacetic acid was concentrated under reduced pressure to give the title compound (54 mg, 0.098 mmol, 94%) as a white solid.
