To a solution of [(1S,2S,3S,4R,5S)-2,3,4-tribenzyloxy-5-[4-chloro-3-[(4-ethoxyphenyl)methyl]phenyl]-6,8-dioxabicyclo[3.2.1]octan-1-yl]methanol 1j (0.36 g, 0.51 mmol, obtained from the synthetic method described in step 9 of example 1) in tetrahydrofuran (7 mL) were added saturated aqueous sodium bicarbonate (7.4 mL), potassium bromide (12 mg, 0.10 mmol) and 2,2,6,6-tetramethylpiperidinooxy (8 mg, 0.05 mmol) in turn at 0° C., and then sodium hypochlorite (6.7 mL, available chlorine ≧5.5%) was added dropwise over a period of 10 min. The mixture was stirred at 0° C. for 2 hours and acidified with aqueous HCl(1N) 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 concentrated in vacuo to give the title compound 2a (0.38 g, 100%) as yellow oil. The crude product was used in next step without further purification. The compound was characterized by the following spectroscopic data: 1H NMR (400 MHz, DMSO-d6) δ (ppm): 13.92 (s, 1H), 7.52 (s, 1H), 7.45 (dd, 2H), 7.30 (dd, 10H), 7.19 (t, 3H), 7.05 (d, 2H), 6.82 (d, 2H), 6.75 (d, 2H), 4.75 (m, 3H), 4.68 (d, 1H), 4.36 (d, 1H), 4.29 (d, 1H), 4.09 (d, 1H), 4.02 (m, 3H), 3.93 (m, 2H), 3.89-3.82 (m, 2H), 3.76 (d, 1H), 1.28 (t, 3H).
