β-内酯亲电体会与多种基于氮的亲核体发生区域选择性加成-消除(AE)或S N 2开环。伯胺和仲胺可促进AE开环,从而提供功能上与酰胺醇醛加合物相同的产品。叠氮化物和磺酰胺阴离子亲核试剂使S N 2内酯开环传递N保护的β-氨基酸衍生物。这些依赖亲核试剂的开环途径,再加上通过酰基卤-醛环缩合反应获得的富含大量庚酮的β-内酯的便捷途径,构成了不对称有机合成的通用方法。还描述了该反应技术在基于从AAC开环序列中出现的旋光性β-叠氮酸的β肽合成新方法中的应用。
Predicting the R/S absolute configuration in asymmetric bifunctional catalysis (ABC)
摘要:
A predictive model for assigning the R/S absolute configuration in chiral Lewis base-dependent asymmetric bifunctional catalysis (ABC) has been developed. Chiral Lewis base (LB*)-dependent ABC abolishes the chiral Lewis acid (LA*) component as the stereochemical determining factor in asymmetric catalysis. By correlating the constant LB* chirality to the facial preference for the LA*-bound carbonyl group for nucleophile delivery, the R/S absolute configuration of the products can be predicted a priori. (c) 2007 Elsevier Ltd. All rights reserved.