To a solution of [(1S,2S,3S,4R,5S)-2,3,4-tribenzyloxy-5-[4-chloro-3-[[4-(trifluoromethoxy) phenyl]methyl]phenyl]-6,8-dioxabicyclo[3.2.1]octan-1-yl]methanol 150 (0.45 g, 0.60 mmol, obtained from the synthetic method described in step 13 of example 15) in tetrahydrofuran (8 mL) were added sodium bicarbonate (0.56 g, 6.62 mmol), potassium bromide (14.3 mg, 0.12 mmol) and 2,2,6,6-tetramethylpiperidinooxy (9.38 mg, 0.06 mmol) in turn at 0° C., and then sodium hypochlorite (19 mL, available chlorine ≧5.5%) was added dropwise over a period of 10 min. The mixture was warmed up to room temperature and stirred for 1 hour, and then acidified with aqueous HCl (1 N) till pH becomes 4. The resulting mixture was extracted with ethyl acetate (10 mL×2). The combined organic layers were washed with saturated aqueous sodium chloride (10 mL), dried over anhydrous sodium sulfate and filtered. The filtrate was concentrated in vacuo to give the title compound 16a (0.50 g, 100%) as yellow oil. This material was not further purified.
