Sodium borohydride → [(3S,4S,5R,6S)-3,4,5-tri-benzyloxy-6-[4-chloro-3-[(2,3-difluoro-4-methoxy-phenyl)methyl]phenyl]-2-(hydroxymethyl)-6-methoxy-tetrahydropyran-2-yl]methanol

(2S,3S,4S,5R,6S)-3,4,5-tribenzyloxy-6-[4-chloro-3-[(2,3-difluoro-4-methoxy-phenyl)methyl]phenyl]-2-(hydroxymethyl)-6-methoxy-tetrahydropyran-2-carbaldehyde 2m (1.29 g, 1.71 mmol) was dissolved in 15 mL of mixed solution (THF and MeOH, v:v=1:2), followed by addition of sodium borohydride (129 mg, 3.42 mmol). The reaction mixture was stirred for 20 minutes. Thereafter, the reaction mixture was concentrated under reduced pressure and partitioned after 30 mL ethyl acetate and 15 mL saturated sodium chloride solution were added. The aqueous phase was extracted with ethyl acetate (15 mL×2) 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 B to obtain the title compound [(3S,4S,5R,6S)-3,4,5-tri-benzyloxy-6-[4-chloro-3-[(2,3-difluoro-4-methoxy-phenyl)methyl]phenyl]-2-(hydroxymethyl)-6-methoxy-tetrahydropyran-2-yl]methanol 2n (520 mg, white solid), with yield: 40%.