A solution of (2S,3R,4S,5S,6R)-2-(4-chloro-3-(4-ethoxybenzyl)phenyl)-6-(hydroxymethyl)-2-methoxytetrahydro-2H-pyran-3,4,5-triol (7.87 g, crude, ˜17.9 mmol) in dichloromethane (59 mL) and acetonitrile (59 mL) was cooled to −30° C. under argon. Triethylsilane (11.5 mL, 71.6 mmole) was added to the reaction solution followed by addition of boron trifluoride etherate (6.8 mL, 53.7 mmole) so that the temperature didn't exceed −10° C. After the addition was complete the reaction solution was stirred for additional 1.5 h and then quenched with 5% sodium bicarbonate until the pH reached 7.5. The organic phase was separated and the aqueous phase was extracted with ethyl acetate (2×80 mL). The combined organic phases were washed with brine (2×80 mL) and dried over anhydrous sodium sulfate. The sample was concentrated under reduced pressure to provide 6.8 g of the title compound as a pale solid which was used for the next step without purification. Yield: 93%. Purity (LCMS-0013) 2.9 min, 82% (UV); MS ESI (m/z) 409[M+1]+, calc. 408.
