Studies of the Selective O-Alkylation and Dealkylation of Flavonoids. VII. Partial Dealkylation of 5, 6, 7-Trioxygenated Flavones and Synthesis of Pectolinarigenin and Its Analogues

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Other Title
  • 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
  • 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-7-5,6,7-三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
  • フラボノイド ノ センタクテキ O アルキルカ オヨビ ダツ アルキルカ ハン

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Description

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°C 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.

Journal

  • YAKUGAKU ZASSHI

    YAKUGAKU ZASSHI 105 (3), 232-239, 1985

    The Pharmaceutical Society of Japan

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