1 ml of a 0.1M solution of boron trifluoride etherate in methylene chloride is added at -15° C., under an inert atmosphere, to a suspension of 250 mg (0.57.10-3 mol) of 2,3,4-tri-O-acetyl-5-thio-α-D-xylopyranosyl trichloroacetimidate, 57 mg (0.48.10-3 mol) of 4-hydroxybenzonitrile and a molecular sieve (1 nm) in 10 ml of methylene chloride. The reaction medium is allowed to return gradually to 0° C. and, after a reaction time of 3 h, is neutralized with sodium bicarbonate. The reaction mixture is then washed with water and dried over magnesium sulfate, MgSO4, and the solvent is evaporated off under reduced pressure. 150 mg (yield: 80%) of the expected product are obtained after purification by chromatography on silica gel using a hexane/ethyl acetate mixture (2/1 v/v) as the eluent.
