A new asymmetric transformation of α-amino-acid esters with (+)-tartaric acid

Abstract

Esters of DL-phenylglycine or substituted phenylglycines, on being stirred with (+)-tartaric acid in alcohols in the presence of carbonyl compounds, give, depending on the reaction conditions, the D- or L-ester hydrogen (+)-tartrates in up to nearly 100% yield (i.e. almost all the racemic ester is converted into the D- or L-salt). The mechanism of this new type of asymmetric transformation is discussed. The D- or L-ester hydrogen (+)-tartrates are hydrolysed by strong acids or strong bases to give amino-acids of high optical purity.