To an ice-cooled solution containing 250 mg of 4',5-dihydroxy-3,3',7-trimethoxyflavone in 10 ml of acetone were alternately added a solution of 400 mg of 2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl bromide in 10 ml of acetone, and 5 ml of 0.8% aqueous sodium hydroxide over 30 minutes, while stirring. After allowing the reaction mixture to stand at room temperature for 3 hours, 20 ml of 0.2% aqueous sodium hydroxide were added thereto. Stirring was continued at room temperature for 3 hours, during which time crystallization took place. The crystals were collected by filtration and recrystallized from ethanol to give 390 mg (80% yield) of 4'-(β-D-glucopyranosyloxy)-5-hydroxy-3,3',7-trimethoxyflavone as pale yellow needles: m.p. 203°-204° C.
