Epimerization, transacylation and bromination of dihydroquercetin acetates; synthesis of 8-bromodihydroquercetin
作者:Eberhard Kiehlmann、Monica Szczepina
DOI:10.2478/s11532-011-0032-8
日期:2011.6.1
acetyl transfer. Dhq 7,3′,4′-triacetate yields exclusively dhq 3′,4′-di- and 3,7,3′,4′-tetraacetate under these conditions. The acetylation/deacetylation reactions are accompanied by partial epimerization: 3 new acetates with 2,3-cis stereochemistry (dhq 3-, 3,7,3′,4′-tetra- and penta-) were identified. Dhq and its 3,7,3′,4′-tetraacetate undergo regiospecific dibromination at C-6 and C-8 with excess N-bromosuccinimide
二氢槲皮素 (dhq) 及其 3-乙酸酯在没有碱催化剂的情况下与乙酸酐反应,生成部分乙酰化产物的混合物。三种新酯通过 NMR 光谱表征为 dhq 3,7,3'-三乙酸酯、3,7,4'-三乙酸酯和 5,7,3',4'-四乙酸酯。在其熔点,纯 dhq 3,7,3',4'-四乙酸酯通过分子间乙酰转移部分转化为 dhq 3,3',4'-三乙酸酯和 dhq 五乙酸酯。在这些条件下,Dhq 7,3',4'-三乙酸酯仅产生 dhq 3',4'-二-和 3,7,3',4'-四乙酸酯。乙酰化/去乙酰化反应伴随着部分差向异构化:鉴定出 3 种具有 2,3-顺式立体化学(dhq 3-, 3,7,3',4'-tetra- 和 penta-)的新乙酸酯。Dhq 及其 3,7,3',