フラボノイドの可溶化に関する研究 (第5報)

クエルセチン-3, 7-ヂメチルエーテルの合成

抄録

In order to determine the structure of quercetin dimethyl ether, m.p. 232-235°, obtained by the methylation of quercetin with diazomethane in the presence of 2 moles of NaH₂BO₃, its alkaline decomposition was attempted but only protocatechuic acid was confirmed and no phenolic portion was obtained in a pure form. Therefore, Allan and Robinson's synthetic method was followed and methoxyphloroacetophenone (V), 3, 4-dibenzyloxybenzoic anhydride (VI), m.p. 128-129°, and potassium 3, 4-dibenzyloxybenzoate were fused to obtain 5, 7-dihydroxy-3-methoxy-3′, 4′-dibenzyloxyflavone (VII), m.p. 189-190°. (VII) was boiled with 1 mole of dimethyl sulfate and potassium carbonate in acetone to yield 5-hydroxy-3, 7-dimethoxy compound (VIII), m.p. 122-123° (acetate, m.p. 162-163°), which was debenzylated by heating in glacial acetic acid with conc. hydrochloric acid to 3′, 4′, 5′-trihydroxy-3, 7-dimethoxyflavone or quercetin-3, 7-dimethyl ether (I), m.p. 234-235° (acetate, m.p. 163-164.5°), which was found to be identical by mixed fusion with the above-mentioned dimethyl ether.