Asymmetric Formal Synthesis of (−)-Cephalotaxine via Palladium-Catalyzed Enantioselective Tsuji Allylation
作者:Zhi-Wei Zhang、Cui-Cui Wang、Hong Xue、Yu Dong、Jian-Hua Yang、Shouxin Liu、Wen-Qing Liu、Wei-Dong Z. Li
DOI:10.1021/acs.orglett.7b04008
日期:2018.2.16
Asymmetric synthesis of the pentacyclic alkaloid (−)-cephalotaxine was accomplished via palladium-catalyzed enantioselective Tsuji allylation for construction of the aza-containing tetrasubstituted stereogenic center (95% yield, 93% ee). The allyl enol carbonate precursor was prepared from Hanaoka’s ketone intermediate, which was formed by a novel formic acid promoted ring-expansion reaction.
五环生物碱(-)-头孢他辛的不对称合成是通过钯催化的对映选择性Tsuji烯丙基化反应完成的,用于构建含氮杂的四取代立体异构中心(产率为95%,ee为93%)。由花冈的酮中间体制得烯丙基碳酸酯烯丙酸酯前体,后者是由新型的甲酸促进的环扩环反应形成的。