申请人:Mars Incorporated
公开号:US20030100775A1
公开(公告)日:2003-05-29
Oligomeric procyanidins containing 4&agr;-linked epicatechin units are rare in nature and have hitherto not been accessible through stereoselective synthesis. Provided herein is the preparation of the prototypical dimer, epicatechin-4&agr;,8-epicatechin, by reaction of the protected 4-ketones with aryllithium reagents derived by halogen/metal exchange from the aryl bromides. Removal of the 4-hydroxyl group from the resulting tertiary benzylic alcohols is effected by tri-n-butyltin hydride and trifluoroacetic acid in a completely stereoselective manner, resulting in hydride delivery exclusively from the &bgr; face.
含有 4&agr;-连接表儿茶素单元的低聚原花青素在自然界中非常罕见,迄今为止还无法通过立体选择性合成获得。本文提供了一种制备原型二聚体表儿茶素-4&agr;,8-表儿茶素的方法,该方法是将受保护的 4-酮与通过卤素/金属交换从芳基溴化物中得到的芳基锂试剂进行反应。氢化三正丁基锡和三氟乙酸以完全立体选择性的方式从生成的叔苄醇中去除 4-羟基,结果氢化物完全从&bgr;面传递。