Total Synthesis of Spinosyn A. 1. Enantioselective Construction of a Key Tricyclic Intermediate by a Multiple Configurational Inversion Scheme
作者:Leo A. Paquette、Zhongli Gao、Zhijie Ni、Graham F. Smith
DOI:10.1021/ja974009l
日期:1998.3.1
the convenient incorporation of a functionalized two-carbon appendage at C-3 and ultimate generation of a cyclohexene double bond after stereochemical inversion at C-7. This scheme leads to 34, a tricyclic compound subsequently shown to be an advanced precursor to the powerful insecticide spinosyn A.
(+)-7,7-二甲氧基降冰片烯-2-one 与源自对映纯溴化物 (+)-11 的铈试剂缩合产生外甲醇,其很容易经历高度立体控制的阴离子氧-Cope 重排。将得到的酮转化为 20,在 C-11(多杀菌素编号)处进行干净的差向异构化,以正确设置该位点的绝对构型。在液氨中用锂还原 20 用于引入全氢作为茚核的两个额外的立体中心。此外,该协议使得在 C-3 处方便地加入功能化的双碳附属物和在 C-7 处立体化学反转后最终生成环己烯双键成为可能。这个方案导致 34,