Oxidation of didehydro-α-amino acids as a route to β-hydroxy-or β-amino-pyruvic derivatives and to α-acylglycinates

Abstract

Oxidation of protected didehydro-α-amino acids with N-bromosuccinimide or lead tetraacetate affords imines of β-bromo- or β-acetoxy-pyruvates. The hydrolysis of brominated imines proceeds through addition of water followed by intramolecular displacement of bromine. According to experimental procedures, intermediate hydroxyaziridines, hydroxyoxazolines or aminoepoxides have to be considered. Two pathways are examined for hydrolysis of β-acetoxyimines: cyclisation to oxazolones or conversion to acylglycinates when imines are converted to the isomeric enamines prior to deprotection.