Under ice cooling, N-methylmorpholine (26 μl, 0.234 mmol) and acetyl chloride (16 μl, 0.234 mmol) were added to a solution of the [6-[(4-chlorophenylsulfonyl)(2,5-difluorophenyl)methyl]pyridin-3-yl]methylamine (40 ing, 0.0978 mmol), which had been obtained in Example 351, in dichloromethane (3 ml). The resulting mixture was stirred at room temperature for 16 hours. Water was added to the reaction mixture, followed by extraction with ethyl acetate. The organic layer was washed successively with water and brine, dried over sodium sulfate and concentrated under reduced pressure. The residue was subjected to flash chromatography on a silica gel column. A fraction obtained from the elution portion with hexane:ethyl acetate=2:3 was concentrated under reduced pressure, whereby the title compound A (low polarity compound) (15 mg, 0.0304 mmol, 40%) was obtained as a white powder and the title compound B (high polarity compound) (12 mg, 0.0266 mmol, 27%) was obtained as a white powder.
