Total Synthesis of (−)-(α)-Kainic Acid via a Diastereoselective Methylenecyclopropane Ring Expansion
作者:Mark E. Scott、Mark Lautens
DOI:10.1021/ol051003p
日期:2005.7.1
[reaction: see text] A concise and enantioselective synthesis of (-)-(alpha)-kainic acid in 13 steps with an overall yield of 15% is reported. The pyrrolidine kainoid precursor with the required C2/C3 trans stereochemistry was prepared with excellent diastereoselectivity (>20:1) via a MgI(2)-mediated ring expansion of a tertiary methylenecyclopropyl amide. A selective hydroboration was then employed
[反应:见正文]报告了13个步骤的简明和对映选择性合成(-)-α-海藻酸的总产率为15%。通过叔甲基亚甲基环丙基酰胺的MgI(2)介导的扩环,以优异的非对映选择性(> 20:1)制备具有所需C2 / C3反立体化学的吡咯烷类化合物前体。然后采用选择性氢硼化来将剩余的立体化学设定在通往(-)-α-海藻酸的C4位。