(Alpinum Isoflavone, 1). To a solution of 8 (250 mg) in dry, freshly distilled benzene (15 ml) was added DDQ (180 mg) and the resulting red solution was refluxed for 30 min, when the colorless hydroquinone separated out. The solid was filtered while hot and the residue was washed with hot, dry benzene. Removal of benzene gave a residue which was purified by column chromatography over silica gel. Elution with chloroform-ethyl acetate (9: l) and ...
