To a solution of [(1S,2S,3S,4R,5S)-2,3,4-tribenzyloxy-5-[4-chloro-3-[(2,3-difluoro-4-methoxy-phenyl)methyl]phenyl]-6,8-dioxabicyclo[3.2.1]octan-1-yl]methanol 210 (0.38 g, 0.49 mmol, obtained from the synthetic method described in step 13 example 21) in tetrahydrofuran (10 mL) were added aqueous sodium bicarbonate (0.46 g, 5.43 mmol), potassium bromide (11.75 mg, 0.10 mmol) and 2,2,6,6-tetramethylpiperidinooxy (7.7 mg, 0.05 mmol) in turn at 0° C., and then sodium hypochlorite (6.8 mL, 8.5 mmol, available chlorine ≧3.5%) was added dropwise. The mixture was stirred at 0° C. for 3 hours and acidified with aqueous HCl (3 N) till pH becomes 6. The resulting mixture was extracted with ethyl acetate (40 mL×2). The combined organic layers were dried over anhydrous sodium sulfate and filtered. The filtrate was concentrated in vacuo to give the title compound 22a (0.37 g, 100%) as yellow oil. This material was not further purified.
