The development and demonstration of short, robust and chromatography-free sequences for the preparation of a (1R,2S)-1-amino-2-vinylcyclopropane-carboxylic acid-derived sulfonamide and ethyl ester in ≥99% ee are described. Both compounds are common building blocks in multiple preparations of potent HCV NS3 protease inhibitors. The robustness of the asymmetric cyclopropanation of (E)-N-benzylideneglycine ethyl ester under phase transfer catalysis conditions is significantly improved based on a detailed mechanistic investigation that included an analysis of the catalyst decomposition pathway, a postulated model for the stereo-selectivity that was guided by calculations and rigorous quality control of the starting materials and reagents. Wet milling has been demonstrated to dramatically accelerate this phase transfer reaction. A bench stable benzylidene-protected primary 1-amino-2-vinylcyclopropane amide intermediate was isolated and its reliable enantiomeric enrichment was achieved by a controlled crystallization process. A chemical resolution procedure was identified using di-p-toluoyl-(D)-tartaric acid to access (1R,2S)-1-amino-2-vinyl-cyclopropanecarboxylic ester in high ee.
本文介绍了一种简短、稳健且无需色谱的序列,用于制备(1R,2S)-
1-氨基-2-乙烯基环丙烷羧酸衍生磺酰胺和
乙酯,其ee值≥99%。这两种化合物是多种强效 HCV
NS3 蛋白酶抑制剂制备过程中常见的基本成分。在相转移催化条件下,(E)-N-亚苄基甘
氨酸
乙酯的不对称
环丙烷化反应的稳健性得到了显著提高,其基础是详细的机理研究,包括催化剂分解途径分析、以计算为指导的立体选择性假定模型以及对起始材料和试剂的严格质量控制。实验证明,湿法研磨能显著加速这种相转移反应。分离出了一种稳定的苯亚甲基保护的 1-
氨基-2-
乙烯基环丙烷酰胺初级中间体,并通过受控结晶过程实现了对映体的可靠富集。利用二对
甲苯甲酰基
酒石酸确定了一种
化学分解程序,从而以高ee值获得了(1R,2S)-
1-氨基-2-乙烯基环丙烷羧酸酯。