Sequential Directed Epoxydation-Acidolysis from Glycals with MCPBA. A Flexible Approach to Protected Glycosyl Donors
作者:Irene Marín、Javier Castilla、M. Isabel Matheu、Yolanda Díaz、Sergio Castillón
DOI:10.1021/jo201165v
日期:2011.12.2
derivatives, respectively, as a result of a syn epoxidation directed by the allylic hydroxyl group, and consecutive ring-opening by m-ClBzOH. When glucal and allal derivatives are fully protected, initial epoxidation proceeds mainly anti to the allylic group to give, after ring-opening, the corresponding pyranosyl chlorobenzoates. Stereoselectivity in the reaction of fully protected galactal derivatives
4,6-二-O-保护的己烯糖和allal衍生物与MCPBA反应得到甘露-和异体-1- ö -米-chlorobenzoate衍生物,分别作为由烯丙基羟基指向的顺式环氧化的结果,并且连续由m - ClBzOH开环。当葡糖醛和烯丙基衍生物得到完全保护时,初始环氧化主要针对烯丙基基团进行,在开环后得到相应的吡喃糖基氯苯甲酸酯。尽管在4,6-和3,4-二-O-保护的衍生物中仅观察到顺式环氧化产物的适度增加,但完全保护的半乳糖衍生物的反应中的立体选择性是完全的。1- ø -米-二氯21的合成中,选择性地保护了氯苯甲酸18并作为供体被活化。