フラボノイドの選択的O-アルキル化及び脱アルキル化反応に関する研究(第7報)5,6,7-三置換フラボン類の部分脱アルキル化反応及びPectolinarigeninとその同族体の合成

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Selective dealkylation of the 5-methoxyl group on the 6-hydroxy-5,7-dimethoxy- and 5,6,7-trimethoxyflavones and of the benzyloxyl groups on the 5,6,7-tris (benzyloxy) flavones was studied and the following results were obtained. (1) The 5-methoxyl group on the flavones lacking hydroxyl groups or the acetates of the flavones having hydroxyl groups was selectively split with an excess of ca. 5% (w/v) anhydrous aluminum chloride-acetonitrile at 60℃ for 1-1.5 h to give quantitatively the corresponding 5-hydroxyflavones. The method is available for the synthesis of 5-hydroxyflavones having 6-hydroxyl or 6-methoxyl groups. (2) The benzyloxyl groups at both the 5- and 6-positions on the 5,6,7-tris (benzyloxy) flavones were selectively split with conc hydrochloric acid in acetic acid to give the corresponding 7-benzyloxy-5,6-dihydroxyflavones. (3) Pectolinarigenin, eupatilin, and 5,7-dihydroxy-3', 4', 5', 6-tetramethoxyflavone were synthesized from the corresponding 5,6,7-trihydroxyflavones by these methods.
公益社団法人日本薬学会の論文
1985-03-25