Stereocontrolled Generation of the (2<i>R</i>) Chroman Core of Vitamin E: Total Synthesis of (2<i>R</i>,4′<i>RS</i>,8′<i>RS</i>)-α-Tocopherol
作者:Gloria Hernández-Torres、Antonio Urbano、M. Carmen Carreño、Françoise Colobert
DOI:10.1021/ol9020783
日期:2009.11.5
(2R,4'RS,8'RS)-alpha-Tocopherol (1) was prepared using, as the two key steps, a novel diastereoselective TiCl4-promoted (S)-sulfoxide-directed allylation of ketal 2 with allyl trimethyl silane 3 to efficiently generate the challenging (2R) stereocenter of the chroman moiety and a cross-metathesis reaction with olefin 4 to efficiently join the lipophilic alkyl chain present in the final target.
(2R,4'RS,8'RS)-α-生育酚(1)的制备采用了两个关键步骤:一种新型的对映选择性TiCl4促进的(S)-亚砜导向的烯丙基化反应,将亚乙基2与烯丙基三甲基硅烷3结合,以高效生成色原酮部分具有挑战性的(2R)立体中心;以及与烯烃4进行交叉复分解反应,以高效连接最终目标中所含的疏水烷基链。