Department of Chemical Sciences, Università di Padova, via Marzolo 1, 35131 Padova, Italy.
Molecules. 2010 Jul 6;15(7):4722-36. doi: 10.3390/molecules15074722.
The regioselective synthesis of several quercetin (3,3',4',5,7-pentahydroxy flavone) tetraesters bearing a single free OH on 5-C was achieved in good yield by proper choice of reaction conditions using common esterification procedures. Tetracetylated quercetin with the free OH on 7-C was selectively obtained instead via imidazole-promoted deacylation of the corresponding pentaester. Unambiguous structural characterization of the two isomeric tetraacetyl quercetin derivatives was obtained by combined HSQC and HMBC 2D-NMR analysis. These molecules can be used as starting materials for the regioselective synthesis of other derivatives. High yield syntheses of the natural polyphenol rhamnetin (7-O-methylquercetin) and of the new mitochondriotropic compound 7-(4-triphenylphosphoniumbutyl) quercetin iodide are reported as examples.
通过选择适当的反应条件，使用常见的酯化程序，成功地以高产率实现了几种带有单个游离 5-C-OH 的槲皮素（3,3',4',5,7-五羟基黄酮）四酯的区域选择性合成。通过相应的五酯的咪唑促进脱乙酰化，可以选择性地获得具有游离 7-C-OH 的四乙酰基槲皮素。通过 HSQC 和 HMBC 2D-NMR 分析的组合，获得了两种异构四乙酰基槲皮素衍生物的明确结构特征。这些分子可用作区域选择性合成其他衍生物的起始材料。作为示例，报道了天然多酚杨梅素（7-O-甲基槲皮素）和新型线粒体靶向化合物 7-（4-三苯基膦丁基）槲皮素碘化物的高产率合成。
