Synthesis of Chiral Building Blocks for Oxygenated Terpenoids through a Simultaneous and Stereocontrolled Construction of Contiguous Quaternary Stereocenters by an Ireland–Claisen Rearrangement
作者:Yoshihiro Akahori、Hiroyuki Yamakoshi、Yuki Sawayama、Shunichi Hashimoto、Seiichi Nakamura
DOI:10.1021/jo402537u
日期:2014.1.17
Methods for highly stereocontrolled syntheses of chiral building blocks with a triad of contiguous stereocenters, including two quaternary ones, have been developed. Ireland–Claisen rearrangement of the (Z)-silyl ketene acetal generated stereoselectively from the (R)-3-methylcyclohex-2-enyl ester derived from an acyclic carboxylic acid proceeded through a chairlike transition state to give the rearranged
已经开发了用于具有三个连续的立体中心(包括两个四元立体中心)的手性构建体的高度立体控制的合成方法。从无环羧酸衍生的(R)-3-甲基环己-2-烯基酯立体选择性生成的(Z)-甲硅烷基烯酮缩醛的爱尔兰-克莱森重排过程经历了椅状过渡态,得到具有S构型的重排产物在羧基的α位。在酸组分中引入环状构象约束,将重排的过渡状态完全转换为船形,从而导致主要生成带有R的产物构型,以四步顺序从中获得假非对映体α-羟基酯。通过碱介导的双消除开环反应获得的烯炔通过Heck反应和所得二烯的区域选择性转化成功地转化成高级中间体,用于合成9-氧化的拉丹烷二萜。