Yang Xiaorong, Xie Zhixiang, Li Ying, Zhang Yuan
State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University 222 Tianshui South Road Lanzhou 730000 P. R. China
Chem Sci. 2020 Apr 18;11(18):4741-4746. doi: 10.1039/d0sc00683a.
The combination of photoredox catalysis and enamine catalysis has enabled the development of an enantioselective aerobic oxidative cross-dehydrogenative coupling between glycine derivatives and simple ketones or aldehydes, which provides an efficient approach for the rapid synthesis of enantiopure unnatural α-alkyl α-amino acid derivatives in good yield with excellent diastereo- (up to >99 : 1) and enantioselectivities (up to 97% ee). This process includes the direct photoinduced oxidation of glycine derivatives to an imine intermediate, followed by the asymmetric Mannich-type reaction with an enamine intermediate generated from a ketone or aldehyde and a chiral secondary amine organocatalyst. This mild method allows the direct formation of a C-C bond with simultaneous installation of two new stereocenters without wasteful removal of functional groups.
光氧化还原催化与烯胺催化相结合,实现了甘氨酸衍生物与简单酮或醛之间的对映选择性有氧氧化交叉脱氢偶联反应,为快速合成对映体纯的非天然α-烷基α-氨基酸衍生物提供了一种有效方法,产率良好,具有出色的非对映选择性(高达>99:1)和对映选择性(高达97% ee)。该过程包括将甘氨酸衍生物直接光诱导氧化为亚胺中间体,随后与由酮或醛以及手性仲胺有机催化剂生成的烯胺中间体进行不对称曼尼希型反应。这种温和的方法能够直接形成C-C键,同时构建两个新的立体中心,而无需进行繁琐的官能团去除操作。