Separation of diastereomers of phosphinic pseudopeptides by capillary zone electrophoresis and reverse phase high-performance liquid chromatography
Capillary zone electrophoresis (CZE) and reverse phase high-performance liquid chromatography (RP-HPLC) were used for separation of diastereomers of phosphinic pseudopeptides in achiral separation media. A set of phosphinic pseudopeptides, i. e. peptides with one peptide bond substituted by phosphinic acid moiety -PO 2 --CH 2derived from the structure N-Ac-Val-AlaB(-CH 2 )Leu-His-NH 2 synthesized as a mixture of four diastereomers was used. Separations of diastereomers by CZE were carried out in Tris-phosphate background electrolytes in the pH range 1.1 -3.2 and at least partial separation of the four diastereomers of each pseudopeptide was achieved. A routinely used RP-HPLC method (C 18 -silica column and water/acetonitrile/trifluoroacetic acid mobile phase) was also capable of resolving the diastereomers. In addition, since individual diastereomers of majority of the pseudopeptides were isolated by RP-HPLC it was possible to check the purity of these RP-HPLC separated diastereomers and to compare the migration order of the diastereomers in CZE with their elution order in RP-HPLC. The results obtained by CZE and RP-HPLC demonstrate a complementarity of both methods in analysis and separation of phosphinic pseudopeptides including their diastereomers.