5-[(5-bromo-2-chloro-phenyl)methyl]-2,3-dihydrobenzofuran 5d (10.0 g, 30.9 mmol) was dissolved in 90 mL of mixed solution (THF and toluene, v:v=1:2) and cooled to −78° C., followed by dropwise addition of a solution of nBuLi in n-hexane (14.83 mL, 37.1 mmol). After stirring for 1 hour at −78° C., a solution of (3R,4S,5R,6R)-3,4,5-tris(trimethylsilyloxy)-6-(trimethylsilyloxymethyl)tetrahydropyran-2-one 2f (15.87 g, 33.9 mmol) in toluene (90 mL) was dropwise added before the reaction mixture was stirred for 3 hours at −78° C. A solution of 0.6 M methanesulfonic acid in methanol (103 mL) was added before the reaction mixture was stirred for 16 hours. Thereafter, the reaction was concentrated under reduced pressure after 100 mL saturated sodium carbonate solution were added. The residue was extracted with ethyl acetate (100 mL×3) after 50 mL saturated sodium chloride solution were added and the organic extract was combined, dried over anhydrous magnesium sulfate, and filtered. The filtrate was concentrated under reduced pressure and the resulting residue was purified by silica gel chromatography with elution system E to obtain the title compound (2S,3R,4S,5S,6R)-2-[4-chloro-3-(2,3-dihydrobenzofuran-5-ylmethyl)phenyl]-6-(hydroxymethyl)-2-methoxy-tetrahydropyran-3,4,5-triol 5e (6.3 g, white solid), yield: 46.7%. 1H NMR (400 MHz, CD3OD): δ 7.53 (d, 1H), 7.45 (dd, 1H), 7.35 (d, 1H), 7.03 (s, 1H), 6.91 (d, 1H), 6.60 (d, 1H), 4.48 (t, 2H), 4.13-3.91 (m, 3H), 3.84-3.73 (m, 2H), 3.61-3.56 (m, 1H), 3.44-3.39 (m, 1H), 3.11 (dd, 3H), 3.07 (s, 3H).
