Studies on Separation of Amino Acids and Related Compounds. III. Separation of Diastereomers of Leucyl Dipeptides by Ion-Exchange Chromatography

Abstract

Abstract A series of experiments on a column chromatography of Dowex 50 with ammonium acetate solvent systems as eluent was carried out in order to find optimal conditions for the separation of the diastereomers of leucylalanine, leucylvaline, leucylleucine and leucyltyrosine. The effects of pH concentration of the salt and alcohols in the solvent systems for the separation of the diastereomers were studied. Among many conditions tested, the change of pH in the solvent system afforded most remarkable influence for the separation; the order of elution of the diastereomers of the dipeptide was found to be inverted at near pH 5.0. On a preparative scale l-leucyl-Dl-valine was successfully separated into the two diastereomers by using a fairly large column. Attempt to separate benzyloxycarbonyl-l-leucyl-Dl-valine benzyl ester with a column of Sephadex LH-20 was described, also.