Glycine and alanine imines as templates for asymmetric synthesis of alpha-amino acids

The present paper is an overview of new methods for the asymmetric synthesi s of different types of alpha-amino acids. These methods are based on alkyl ation and condensation reactions of glycine and alanine imine derivatives, which can be carried out under very mild and simple reaction conditions. Th e enolates generated from these types of reagents are very soft and can be alkylated in a highly diastereoselective manner, even at room temperature, by using chiral templates or asymmetric PTC conditions. These methodologies afford monoalkylated and dialkylated alpha-amino acids as well as heterocy clic derivatives. In the case of cyclic imine derivatives with oxazinone or pyrazinone structures, the condensation reaction under PTC conditions or w ith Eschenmoser's salt allows the preparation of chiral alpha,beta-didehydr o-alpha-amino acid derivatives which can be hydrogenated, cyclo-propanated or submitted to Diels-Alder cycloadditions to afford N-methylated and cycli c alpha-amino acids.