Evaluation and Comparison of a 3,5-Dimethylphenyl Isocyanate Teicoplanin with Phenyl Isocyanate Teicoplanin Chiral Stationary Phase Using RP-HPLC

HPLC enantiomeric separations of 8 a-amino acids were achieved using two self-made chiral stationary phases (CSP)phenyl isocyanate teicoplanin (Phe-TE) and 3,5-dimethylphenyl isocyanate teicoplanin (DMP-TE), using reversed phase mobile phases. The Phe-TE or the DMP-TE CSP was prepared from the TE using derivative agents, phenyl isocyanate or 3,5-dimethylphenyl isocyanate, respectively. The chromatographic results were given as the retention, selectivity, resolution factor and the enantioselective free energy difference corresponding to the separation of the two enantiomers. The effect of pH, organic modifier type and amount were discussed, and the stereoselectivities for two TE-based CSPs were compared. The chiral selectivity factor for six a-amino acids on DMP-TE is somewhat bigger than that on Phe-TE CSP under reversed phase (RP) mode. Comparison of the enantiomeric separations using self-made Phe-TE and DMP-TE was conducted to gain a better understanding of the chiral recognition mechanism of the macrocyclic glycopeptide CSP.