Synthesis of <i>erythro</i>- and <i>threo</i>-γ-Hydroxy-<scp>l</scp>-ornithines

Abstract

Abstract γ-Hydroxy-Dl-ornithine was obtained from an alkaline hydrolysate of 2,5-diamino-4-pentanolide synthesized according to the method of Talbot et al. The amino acid preparation was found to be a racemic mixture composed of 34% erythro and 66% threo isomers by a new chromatographic assay. This assay is based on the conversion of the basic amino acid to a neutral amino acid by acetylation of the δ-amino group and the analysis of the resulting Nδ-acetyl derivative with an automatic amino acid analyzer by the ordinary method. Two diastereoisomers of γ-hydroxy-Dl-ornithine were separated by column chromatography on Dowex 50 and isolated as their crystalline hydrochlorides. Guanidination of the separated racemic diastereoisomers gave the corresponding diastereoisomeric γ-hydroxyarginines, hydrolysis of which with arginase yielded erythro- and threo-γ-hydroxy-Dl-ornithines.