New strategy for the synthesis of ladybird beetle azaphenalene alkaloids using a combination of allylboration and intramolecular metathesis. Total synthesis of (±)-Hippocasine and (±)-epi-Hippodamine
作者:N. Yu. Kuznetsov、S. E. Lyubimov、I. A. Godovikov、Yu. N. Bubnov
DOI:10.1007/s11172-014-0464-3
日期:2014.2
was involved in the second key step, the intramolecular allylic amination upon treatment with a [Pd] or an [Ir] catalyst giving diastereomeric bicyclic terminal dienes (∼1: 1), which were separated by chromatography. The stereochemistry of one of the dienes is the same as that in alkaloid Hippocasine. The third key step (the intramolecular metathesis reaction) includes the final assembly of the azaphenalene
基于烯丙基硼化反应和分子内复分解的组合,开发了一种组装瓢虫氮杂菲烯生物碱(瓢虫)三环骨架的新策略。第一个关键步骤是 4-甲基吡啶与(4,4-二乙氧基丁基)锂的 1,2-有机锂化,随后与三烯丙基硼烷进行还原烯丙基化,生成反式-2-烯丙基-6-(4,4-二乙氧基丁基)- 4-甲基-1,2,3,6-四氢吡啶。4,4-二乙氧基丁基取代基分四步进一步转化为4-乙酰氧基-5-己烯基,所得产物参与第二个关键步骤,即用[Pd]或[Ir]处理后的分子内烯丙基胺化] 催化剂产生非对映双环末端二烯(~1:1),通过色谱分离。其中一种二烯的立体化学与生物碱 Hippocasine 的立体化学相同。第三个关键步骤(分子内复分解反应)包括氮杂菲那烯系统的最终组装。获得的三环衍生物包含两个不同取代的 C=C 键,其中一个 (Pd/C) 的选择性氢化产生 (±)-Hippocasine,而彻底氢化产生 (±)-epi-Hippamine。