Direct high‐performance liquid chromatographic enantioseparation of α‐substituted proline analogues on a quinine‐derived chiral anion‐exchanger stationary phase

Abstract

Abstract Use of a quinine‐derived chiral anion‐exchanger stationary phase for the direct high‐performance liquid chromatographic enantiomer separation of N ‐protected unusual α‐substituted proline analogues is reported. The chromatographic conditions (eluent composition, pH, and buffer concentration) were varied to achieve optimal separation. The readily prepared 2,4‐dinitrophenyl derivatives were well separable, with good efficiency and high resolution. The elution sequences of the enantiomers of the derivatives were determined. Knowledge of the elution sequence allows identification of the configuration of the α‐substituted proline analogues in peptide epimers resulting from use of the racemates in the peptide synthesis. The method also proved suitable for determination of the enantiomeric purity of proline analogues obtained by asymmetric synthesis.