Enantiomeric high-performance liquid chromatographic separation of β-substituted tryptophan analogues

The high-performance liquid chromatographic enantioresolution of beta-substituted tryptophan analogues by direct and indirect methods is reported. The direct separation was carried out on chiral crown ether-bonded, on the macrocyclic antibiotic teicoplanin-bonded or on different derivatized beta-cyclodextrin-bonded phases. The indirect resolution was achieved by applying pre-column derivatization with the chiral reagents 1-fluoro-2,4-dinitrophenyl-5-L-alanine amide (FDAA) and 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl isothiocyanate (GITC). In the separation of all four isomers of the analytes, the indirect methods seemed to be more efficient than the direct methods. In most cases, the FDAA derivatives of the stereoisomers could be separated with better selectivity in methanol-containing mobile phases.