Inverse stereoselectivity in the nucleophilic attack on five-membered ring oxocarbenium ions. Application to the total synthesis of 7-epi-(+)-goniofufurone
作者:Luís Hernández-García、Leticia Quintero、Herbert Höpfl、Martha Sosa、Fernando Sartillo-Piscil
DOI:10.1016/j.tet.2008.10.087
日期:2009.1
A highly stereoselective nucleophilic substitution at the anomeric position of 1,2-O-isopropylidene furanose derivatives was employed for the synthesis of 7-epi-(+)-goniofufurone and two of its stereoisomers. According to Woerpel's model, the stereoselectivity depends essentially on stereoelectronic factors that lead to a preferred nucleophilic attack on the inside face of the five-membered ring oxocarbenium
在1,2- O-异亚丙基呋喃糖衍生物的异头位置上的高度立体选择性亲核取代被用于合成7- epi -(+)-goniofufurone及其两个立体异构体。根据Woerpel模型,立体选择性主要取决于立体电子因素,这些因素会导致以折叠构象对五元环氧碳鎓离子内表面进行优选的亲核攻击,从而立体化学结果通常由C3位置的取代基控制(或组)。本文中,我们通过在木糖的C5位置放置一个乙酰基,开发了一种反向立体选择性亲核取代的策略呋喃糖环,现在导致在各自的氧碳鎓离子的外面进行亲核反应。使用这种方法,从双丙酮d-葡萄糖衍生物开始,我们能够以七个步骤完成强力抗肿瘤化合物7- epi -(+)-goniofufurone的全合成,总收率高达33%。