32 3-Hydroxy-および3-Methoxyflavone類の光酸化 : 生体内酸化のモデル

概要

論文の詳細を見る
It has been reported that quercetin (Ib) is oxidized to 2-protocatechuoyl phloroglucinol carboxylic acid (II) and carbon monoxide by dioxygenases from Aspergillus species. In view of the resemblance between action of some oxygenases and photosensitized oxygenation, we have carried out photosensitized oxygenation of 3-hydroxyflavones. In a typical run, a solution of quercetin 5,7,3',4'-tetramethyl ether (III) and rose bengal(sensitizer)in pyridine was irradiated with a tungsten lamp or a high-pressure mercury arc lamp under bubbling oxygen. Methylation of the crude products with diazomethane followed by column chromatography afforded depside (IV), its hydrolysed products, carbon dioxide and carbon monoxide. The results are summarized in Table I and II, which show that the presence of a 3-hydroxy group is prerequisite for this oxidation, and a possible reaction mechanism is illustrated in Scheme I. On the other hand, it was found that photoxidation of 3-methoxyflavones caused a quite different type of reaction. Ultraviolet irradiation of 3-methoxyflavone (XXII) under bubbling oxygen yielded the chromono-isocoumarin derivative (XXIII), which has the same carbon skelton as an uncommon flavonoid, distemonanthin (XVIII). This cyclization raises some speculations on the biosynthesis of uncommon flavonoid.
天然有機化合物討論会の論文
1967-09-25