Synthesis by Using Chirality of l-Ephedrine : Asymmetric Synthesis of Alanine and Phenylglycine

Abstract

The chiral hydrazone compounds (IVa and IVb) were obtained by the condensation of methyl pyruvate and ethyl phenylglyoxylate with l-ephedrine-N-amine. Reduction of the C=N group in these compounds was carried out using Pd-C (10%) catalyst in ethanol at room temperature, followed by hydrogenolysis of the N-N linkage using the same catalyst in acidic ethanol solution under pressure of 3-4 kg/cm² at 50-60°, and amino acid esters and l-ephedrine were obtained. Alanine and phenylglycine formed by hydrolysis of amino acid esters afforded R configuration with optical purity of 38% and 37%, respectively. The optical purity of l-ephedrine decreased only by 3.4% and 1.5% in several case during a cycle of the amino acid synthesis using l-ephedrine as a chiral reagent.