Indirect enantioseparation of α-amino acids by reversed-phase liquid chromatography using new chiral derivatizing reagents synthesized from s-triazine chloride

Ten chiral dichloro- and monochloro-s-triazines were prepared by the nucleophilic displacement of chlorine atom(s) in s-triazine chloride and its 6-methoxy derivative with different amino acid amides. Dichloro-s-triazines (DCTs) were used as CDRs for derivatization of α-amino acids under basic conditions at room temperature (30 °C) while derivatization with monochloro-s-traizine (MCT) reagents was carried out at 80 °C. The resultant diastereomers were separated on a reversed-phase C18 column using mixtures of acetonitrile and aqueous-trifluoroacetic acid (TFA). The separation results for the two were compared. One DCT reagent was optimized for derivatization kinetics with respect to the effects of pH, reagent excess, temperature and reaction time on derivatization yield. In most of the cases, DCT reagents provided better separation of diastereomers in comparison to MCT reagents. One DCT reagent was also validated for limit of detection, linearity, recovery and robustness. Effects of structural modifications in reagents on chromatographic properties were investigated. Separation mechanism of diastereomers was proposed in light of both MCT and DCT reagents.