Practical synthetic methods of natural cardenolides are illustrated in the syntheses of xysmalogenin and digitoxigenin. The new routes employ pregn-14-en-20-one as key intermediate which was prepared by partial reduction of 14, 16-dien-20-one with triphenylstannane or triethylsilane. A general and efficient method was devised for obtaining cardenolides consisting of (1) 21-methylsulfenylation of pregnen-20-one, (2) the reaction of the resulting 21-methylthio derivative with bromoacetate and zinc, (3) alumina chromatography of epoxy ester obtained from the S-methylated Reformatsky product.
天然卡登诺酮的实用合成方法在xysmalogenin和digitoxigenin的合成中得到了展示。这些新路线使用孕苯-14-烯-20-酮作为关键中间体,该中间体通过用三苯基
锡或三乙基
硅烷对14, 16-二烯-20-酮进行部分还原制备。设计了一种通用且高效的方法来获得卡登诺酮,包括:(1)孕烯-20-酮的21-甲基亚
硫酰化;(2)将得到的21-甲基
硫衍
生物与
溴乙酸酯和
锌反应;(3)对从S-甲基化Reformatsky产物中获得的环氧酯进行铝土矿柱层析。