Asymmetric synthesis of a taxol C-ring by aldol condensation and radical cyclization
作者:David Crich、Xian-Yun Jiao、Milan Bruncko
DOI:10.1016/s0040-4020(97)00412-2
日期:1997.5
the asymmetric synthesis of a fully functionalized C-ring is described. Two asymmetric aldol reactions (Evans) are used to create the C5 and C7 stereocenters and the diastereoselective alkylation of a stereochemically and conformationally biased dioxanone to introduce, with the correct relative and absolute stereochemistry, the quaternary center at C8. Vinyl radical cyclization is used to close the C2
在紫杉醇的收敛方法的背景下,描述了完全官能化的C环的不对称合成。使用两个不对称的醛醇缩合反应(Evans)来创建C5和C7立体中心,以及立体化学和构象偏向的二恶烷酮的非对映选择性烷基化,以正确的相对和绝对立体化学引入C8的季中心。乙烯基自由基环化用于以良好收率关闭C2,3键。这种非对映选择性自由基环化可能通过椅子状过渡态进行,其中最大数目的取代基被赤道排列。