Enantioselective Synthesis of beta-Amino Acids: TMS-SAMP as a Chiral Ammonia Equivalent for the Aza Analogous Michael Addition to alpha,beta-Unsaturated Esters

摘要

beta-Amino acids A have achieved premier importance as substructures of numerous biologically active natural products as well as building blocks for beta-Mactam antibiotics. This is reflected by the ever increasing research activity in the field of their stereoselective synthesis. One approach to this class of compounds makes use of enantiomerically pure building blocks provided by nature, for example aspartic acid. On the other hand an increasing number of methods based on asymmetric synthesis can be applied. Besides numerous methodologies For C-C bond formation some asymmetric approaches to C-N bond connections in accordance with the retrosynthetic analysis A=>B have been developed in the recent past. Using aza analogous Michael additions, achiralN-nucleophiles can be added to chi-ral Michael acceptors. Alternatively chiral donors of amine functionality, especially N-silylated amides, have proven to be versatile soft nucleophiles, for example C can be added to chi/beta-unsaturated ester D as achiral Michael acceptor.