Syntheses of Nuclear-substituted Flavonoids and Allied Compounds. IX. Syntheses of Tetramethyl Ether and Dimethyl Ether of Ginkgetin

Abstract

2-Acetyl-3, 5-dimethoxyphenyl 3-iodoanisate (X) and its 6-iodo isomer (XT) were 1 espectively isomerized to diketones (XII, XIII) by means of potassium hydroxide in pyridine, and then cyclized to flavone compounds (XIV, XV), which were finally condensed each other to biflavonyl (XVI) by refluxing in dimethylformamide for 4 hours in the presence of activated natural copper powder. The yield of crude product was 28%. Biflavonyl (XVI) was demethylated to (XVII), when it was treated with aluminum chloride in nitrobenzene at 110°for 1 hour (XVI) and (XVII) were identified respectively with tetramethyl ether and dimethyl ether of ginkgetin in C, H-analyses, mixed melting points and infrared absorption spectra.