Total Synthesis of (+)-Brasilenyne. Application of an Intramolecular Silicon-Assisted Cross-Coupling Reaction
作者:Scott E. Denmark、Shyh-Ming Yang
DOI:10.1021/ja0466863
日期:2004.10.1
3-cis,cis diene unit was accomplished with a tandem ring-closing metathesis/silicon-assisted intramolecular cross-coupling reaction. In addition, a key propargylic stereogenic center was created through a novel, highly diastereoselective ring opening of a 1,3-dioxolanone promoted by TiCl(4). This reaction proceeded through an oxocarbenium ion intermediate and the asymmetric induction was fully controlled
(+)-brasilenyne (1) 的第一个对映选择性全合成已在 19 个线性步骤中实现,1-(S)-苹果酸的总产率为 5.1%。包含 1,3-cis,cis 二烯单元的 oxonin 核心的构建是通过串联闭环复分解/硅辅助分子内交叉偶联反应完成的。此外,一个关键的炔丙基立体中心是通过由 TiCl(4) 促进的 1,3-二氧戊环的新型、高度非对映选择性环开口创建的。该反应通过氧代碳正离子中间体进行,不对称诱导完全由 l-苹果酸残基控制。C(8) 立体中心由试剂控制的不对称烯丙基硼化设置。