我们描述了总合成盐素A的全部细节,该盐是一种大环天然产物,被建议源自常见的生物合成中间体,即苦味素A。合成路线的核心是战略性地使用硝基甲烷进行多种用途:(1)作为一种合成油氨基甲基的替代物;(2)作为高度对映选择性催化不对称共轭物的理想亲核试剂,以锻造具有挑战性的全碳四元立体异构中心,该中心被用来诱导分子的所有其他手性中心的形成;和(3)作为C 1 N 1构建单元以形成3-氮杂双环[3.3.1]壬烷框架。该策略的实现依赖于新的有机催化不对称的硝基甲烷共轭加成反应,将硝基甲烷添加到3-烯基环己二-2-烯酮中,以及第一个由Pd促进的硫代氨基甲酸酯部分分子内偶联到电子缺陷的烯(烯酮)上。形成3-氮杂双环[3,3,1]壬烷核。该合成还具有烯酮与醛的SmI 2介导的分子间还原偶联,闭环的烯烃和炔烃复分解反应以构建两个氮杂大环,以及烯醇史无前例的直接转化为烯酮。
Three keys to success: A concise method for the construction of a tricyclicsubstructure (2) of haliclonin A (1) in racemic form is described (see figure). This synthesis features a new Pd‐mediated chemoselective carbonyl–enone coupling reaction, an organocatalytic reaction, and a ring‐closing metathesis reaction for the construction of the macrocyclic ring as key steps.
The first totalsynthesis of the alkaloid (−)‐haliclonin A is reported. The asymmetricsynthesis relied on a novel organocatalytic asymmetric conjugate addition of nitromethane with 3‐alkenyl cyclohex‐2‐enone to set the stereochemistry of the all‐carbon quaternary stereogenic center. The synthesis also features a Pd‐promoted cyclization to form the 3‐azabicyclo[3,3,1]nonane core, a SmI2‐mediated intermolecular
AlCl<sub>3</sub>‐Promoted Conia‐Ene‐Related Cyclization of α,ω‐Diethylenic Ketones and 1,2‐ or 1,3‐Hydroalkenylation of Unactivated Cyclopropanes
作者:Julien Coulomb
DOI:10.1002/adsc.202300317
日期:2023.9.5
α,β-Unsaturated enones possessing an unactivated olefin at the ϵ-, ζ- or η-position underwent an aluminum chloride-promoted Conia-ene-related cyclization, affording unsaturated decalones or hexahydroindenones in generally good yields. Cyclopropanes could be used as olefin surrogates in this process, leading to the same bicyclic products in slightly improved efficiency as the result of 1,2- or 1,3-hydroalkenylation