Asymmetric nucleophilic substitution of α-bromo amides via dynamic kinetic resolution for the preparation of dipeptide analogues
作者:Jiyoun Nam、Ji-yeon Chang、Eun-kyoung Shin、Hyun Jung Kim、Yangmee Kim、Soonmin Jang、Yong Sun Park
DOI:10.1016/j.tet.2004.05.094
日期:2004.7
Asymmetric nucleophilic substitution reactions of α-bromo α-aryl acetamides derived from l-amino acids are described. The simple and practical syntheses of dipeptide analogues have been developed with dibenzylamine, TBAI and a base to provide 2a–2n and 4 in 50–98% yields with diastereomeric ratios from 74:26 to >99:1. Mechanistic investigations suggest that α-bromo acetamides are configurationally
描述了衍生自1-氨基酸的α-溴α-芳基乙酰胺的不对称亲核取代反应。用二苄基胺,TBAI和碱开发了二肽类似物的简单实用合成方法,以50-98%的产率提供2a - 2n和4,非对映体比例为74:26至> 99:1。机理研究表明,α-溴乙酰胺在反应条件下构型不稳定,不对称诱导的主要途径是动态动力学拆分。1b的两个差向异构过渡态的半经验计算发现(αS-epimer是反应更快的差向异构体,形成分子间氢键,促进了胺亲核试剂的传递。