A mixture of methyl 5-(4-(1H-pyrazol-1-yl)benzyl)-3-fluoro-2-formyl-4-methylbenzoate (7.97 g), (3S,4S)-3-aminotetrahydro-2H-pyran-4-ol (2.65 g), anhydrous magnesium sulfate (5.23 g) and THF (160 mL) was stirred at room temperature for 5 hr under nitrogen atmosphere. The insoluble substance was removed by filtration, and the filtrate was concentrated. The residue was dissolved in a mixed solvent of methanol (120 mL)-THF (150 mL), sodium triacetoxyborohydride (9.59 g) was added thereto, and the mixture was stirred at room temperature for 15 hr. Sodium triacetoxyborohydride (9.59 g) was again added thereto, and the mixture was stirred for 3 hr. The reaction mixture was diluted with ethyl acetate, and the mixture was washed with water and saturated brine. The organic layer was dried over anhydrous magnesium sulfate, and the solvent was evaporated under reduced pressure. The residue was dissolved in DMSO-toluene, and the solution was purified by NH silica gel column chromatography (ethyl acetate/hexane). The obtained crude product was dissolved in THF, the solution was washed with water and saturated brine, and the solvent was evaporated under reduced pressure. The residue was washed with a mixed solvent of diisopropyl ether-ethyl acetate to give a crude product. The crude product (5.28 g) was dissolved in hot ethanol (60 mL), and recrystallized over 4 hr under ice-cooling to give the title compound (4.88 g).
