Beemelmanns Christine, Reissig Hans-Ulrich
Institut für Chemie und Biochemie, Freie Universität Berlin, Takustrasse 3, 14195 Berlin (Germany).
Leibniz Institute for Natural Product Research and Infection Biology e.V., Hans-Knöll-Institute (HKI), Beutenbergstrasse 11 a, 07745 Jena (Germany).
Chemistry. 2015 Jun 1;21(23):8416-25. doi: 10.1002/chem.201500094. Epub 2015 Apr 15.
This comprehensive report accounts the development of a highly diastereoselective samarium diiodide-induced cascade reaction of substituted indolyl ketones. The complexity-generating transformation with SmI2 allows the diastereoselective generation of three stereogenic centers including one quaternary center in one step. The obtained tetra- or pentacyclic dihydroindole derivatives are structural motifs of many monoterpene indole alkaloids, and their subsequent transformations gave way to one of the shortest approaches towards strychnine (14 % overall yield in ten steps, or 10 % overall yield in eight steps). During the course of this report we discuss the influence of substituents on the cyclization step, plausible mechanistic scenarios for the SmI2 -induced cascade reaction, diastereoselective reductive amination, and regioselective dehydratization protocols towards the pentacyclic core structure of strychnos alkaloids.
本综合报告阐述了二碘化钐引发的取代吲哚基酮的高非对映选择性串联反应的发展情况。二碘化钐引发的这种产生复杂性的转化反应能够一步非对映选择性地生成三个立体中心，其中包括一个季碳中心。所得到的四环或五环二氢吲哚衍生物是许多单萜吲哚生物碱的结构基元，随后对它们进行的转化反应为士的宁的最短合成路线之一提供了可能（十步总产率为14%，或八步总产率为10%）。在本报告撰写过程中，我们讨论了取代基对环化步骤的影响、二碘化钐引发的串联反应可能的机理、非对映选择性还原胺化反应以及针对马钱子生物碱五环核心结构的区域选择性脱水方案。
