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Biomimetically Inspired, One-Step Synthesis of Exotine A and Exotine B
The Journal of Organic Chemistry ( IF 3.6 ) Pub Date : 2020-09-14 , DOI: 10.1021/acs.joc.0c01524
Lance T Lepovitz 1 , Stephen F Martin 1
Affiliation  

The one-step syntheses of exotine A and exotine B, which comprise the unusual coumarin-cyclohepta[b]indole ring system, have been achieved via the biomimetically inspired combination of indole, prenal, and either trans-dehydroosthol or gleinadiene. This facile three-component reaction delivered a mixture (17:1) of exotine A and 11′-epi-exotine A in a 43% yield from trans-dehydroosthol and a mixture (4:1) of exotine B and 11′-epi-exotine B in a 50% yield from gleinadiene. Some mechanistic aspects of this process were explored, and spectral evidence for 3,3′-spiroindolenine intermediates was obtained. Moreover, a skeletal isomer of exotine A that likely originates from a 1,2-alkyl rearrangement of a protonated 3,3′-spiroindolenine was isolated and characterized by X-ray crystallography. These findings not only provide experimental support for Jiang’s proposed biosynthesis of exotine A and exotine B but also foreshadow the existence of other exotine-derived natural products having isomeric frameworks. Exploratory attempts to induce an enantioselective 3CR using a chiral phosphoric acid were unsuccessful.

中文翻译:

Exotine A 和 Exotine B 的仿生一步合成

exotine A 和 exotine B 的一步合成,包括不寻常的香豆素-环庚烷 [ b ] 吲哚环系统,是通过仿生的吲哚、prenal 和反式脱氢鱼油醇或 gleinadiene 的组合实现的。这种简便的三组分反应提供了 exotine A 和 11'- epi -exotine A的混合物 (17:1),从反式-脱氢鱼腥草中以 43% 的产率提供了 exotine B 和 11'- epi的混合物 (4:1)-exotine B 以 50% 的收率从 gleinadiene 中得到。探索了该过程的一些机械方面,并获得了 3,3'-螺吲哚中间体的光谱证据。此外,外汀 A 的骨架异构体可能源自质子化 3,3'-螺吲哚的 1,2-烷基重排,并通过 X 射线晶体学进行表征。这些发现不仅为Jiang提出的exotine A和exotine B的生物合成提供了实验支持,而且预示了其他具有异构框架的exotine衍生的天然产物的存在。使用手性磷酸诱导对映选择性 3CR 的探索性尝试没有成功。
更新日期:2020-09-14
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