3-(5-Benzo[b]furanyl)-2'-(β-D-glucopyranosyloxy)-6'-allyloxy-4'-methylpropiophenone (300 mg) obtained in Example 2 is dissolved in tetrahydrofuran (3 ml), and thereto are added 2,4,6-collidine (315 mg) and diphenyl chlorophosphate (486 mg) under ice-cooling. The mixture is stirred at room temperature for 22 hours under argon atmosphere. The reaction mixture is poured into chilled 10% aqueous citric acid solution, and extracted with ethyl acetate. The organic layer is washed successively with water, a saturated aqueous sodium hydrogen carbonate solution, and a saturated aqueous sodium chloride solution, dried, and concentrated under reduced pressure. The residue is purified by silica gel column chromatography (solvent; chloroform/methanol) to give 3-(5-benzo[b]furanyl)-2'-(6-O-diphenylphosphono-β-D-glucopyranosyloxy)-6'-allyloxy-4'-methylpropiophenone (327 mg).
