Studies of the Selective<i>O</i>-Alkylation and Dealkylation of Flavonoids. VI. Demethylation of 8-Hydroxy-5,7-dimethoxyflavones with Anhydrous Aluminum Chloride or Bromide in Acetonitrile
作者:Tokunaru Horie、Hiroki Kourai、Nobuhisa Fujita
DOI:10.1246/bcsj.56.3773
日期:1983.12
with anhydrous aluminum chloride or bromide in acetonitrile was studied and the following results were obtained. (1) Anhydrous aluminum chloride in acetonitrile selectively split the 5-methoxyl group without cleavage of the 7-methoxyl group, and seven 5,8-dihydroxy-7-methoxy-flavones were quantitatively synthesized by the demethylation. (2) In the demethylation with anhydrous aluminum bromide, the
研究了七种 8-羟基-5,7-二甲氧基黄酮与无水氯化铝或溴化铝在乙腈中的脱甲基反应,得到以下结果。(1)无水氯化铝在乙腈中选择性裂解5-甲氧基而不裂解7-甲氧基,通过脱甲基作用定量合成7个5,8-二羟基-7-甲氧基-黄酮。(2) 在无水溴化铝脱甲基反应中,4',5,7-三甲氧基-和3',4',5,7-四甲氧基-8-羟基黄酮上的5-和7-甲氧基被选择性裂解得到相应的5,7,8-三羟基黄酮收率良好。然而,去甲基化不能用于合成 5,7,8-trihydroxy-3',4',5'-trimethoxyflavone, 4',5,7,8-tetrahydroxy-3'-methoxy-, 和 3' ,5,7,8-四羟基-4'-甲氧基黄酮,因为 B 环上的甲氧基裂解。合成的黄酮被用于鉴定两种天然黄酮,它们被认为是4',5,8-tri...