The compound obtained in Example 2 (252 mg, 0.60 mmol) and triethylamine (0.201 ml) were dissolved in THF (5 ml), and under ice cooling, to the solution was added methanesulfonyl chloride (0.093 ml). The mixture was stirred at the same temperature for 1 hour. The compound obtained in Example 2 (252 mg, 0.60 mmol) and triethylamine (0.201 ml) were dissolved in THF (5 ml). To the solution was added methanesulfonyl chloride (0.093 ml) under ice cooling with stirring, and the mixture was stirred at the same temperature for 1 hour. To the mixture was added a saturated aqueous solution of sodium hydrogencarbonate (15 ml) under ice cooling, and the mixture was extracted with ethyl acetate (15 ml×3). The organic layer was dried over magnesium sulfate and concentrated under reduced pressure. The concentrate was subjected to column chromatography (silica gel 10 g, ethyl acetate/methanol=1/0 to 9/1), and the desired fraction was concentrated under reduced pressure. To the concentrate was added diisopropyl ether (100 ml), and the resulting precipitates were collected by filtration. The precipitates were washed with diisopropyl ether, and dried under reduced pressure to give the titled compound (110 mg, 0.22 mmol, Yield 37%) as white crystals.
