madangamine E 的对映选择性全合成分 30 个步骤完成,这是通过一种新的催化和高度对映选择性去对称分子内迈克尔加成反应实现的-二取代硝基烯烃。这一关键的碳-碳键形成反应有效地构建了具有近乎完美的对映和非对映选择性的手性双环核心,同时建立了三个立体中心,包括一个季碳,并被证明具有高度可扩展性。此外,使用密度泛函理论(DFT)计算探索了这种催化环化中对映选择性的途径和起源,揭示了对映确定步骤中关键的底物/催化剂相互作用。构建双环核心后,即可完成 madangamine E 的全合成,关键步骤包括氨基醇的温和一锅氧化内酰胺化、两步Z-空间位阻酮的选择性烯化和闭环复分解以安装两个大环。
An enantioselective desymmetric nucleophilic α‐addition of cyclohexanone to propiolamide has been developed through a 6‐exo‐dig cyclization reaction. By employing simple and readily available L‐proline sodium salt as a bifunctional catalyst, a series of chiral 6,6‐bicyclic bridged products bearing morphan scaffold have been isolated in good yields and excellent enantioselectivities. Density functional
Enantioselective Desymmetrization of Prochiral Cyclohexanones by Organocatalytic Intramolecular Michael Additions to α,β-Unsaturated Esters
作者:Adam D. Gammack Yamagata、Swarup Datta、Kelvin E. Jackson、Linus Stegbauer、Robert S. Paton、Darren J. Dixon
DOI:10.1002/anie.201411924
日期:2015.4.13
cyclohexanediamine‐derived primary amine organocatalyst, a range of prochiral cyclohexanone derivatives possessing an α,β‐unsaturated ester moiety linked to the 4‐position afforded the bicyclic products, which possess three stereogenic centers, as single diastereoisomers in high enantioselectivity (83–99 % ee) and in good yields (60–90 %). Calculations revealed that stepwise CC bond formation and proton transfer