To an ice-cooled solution of Compound 46 (1.22 g, 1.01 mmol) in methylene chloride (15 ml), a methylene chloride solution containing 10% trifluoroacetic acid (7 ml) was added, and water (650 μl) was further added thereto, after which the ice bath was removed, and this was followed by stirring at room temperature for 30 minutes. Triethylamine was poured to the reaction solution, and this was followed by concentration under reduced pressure. The residue obtained was subjected to silica gel column chromatography (Yamazen YFLC Gel, eluent (ethyl acetate-ethyl acetate:methanol 9:1)) to yield Compound 47 (light-yellow oil 977 mg, Y. quant.).
