Reversed-phase high-performance liquid chromatographic separation of theα- andβ-isomers of aspartyl peptides

A high-performance liquid chromatography method is described for the separation of the α- and β-isomers of aspartyl-containing peptides such as N-benzyloxycarbonyl methyl aspartate, protected sweet dipeptide and delta sleep inducing peptide (DSIP, a nonapeptide). The α- and β-isomers were separated on a column containing octadecyl silica bonded-phase packing under reversed-phase conditions using methanol-water as the mobile phase containing a small amount of acetic acid. The resolution achieved meets the requirements of qualitative and quantitative analysis. This method is also suited for the determination of intermediates in the aspartyl peptide synthesis.