High-performance liquid chromatographic separation of the enantiomers of unusual alpha-amino acid analogues

The direct and indirect stereochemical resolution of the enantiomers of rin g- and alpha-methyl-substituted phenylalanines and phenylalanine amides was attempted by high-performance liquid chromatographic methods. The direct s eparation was carried out on two chiral stationary phases, the crown-ether- based Crownpak CR(+), and the teicoplanin-based Chirobiotic T, while the in direct resolution was performed by applying pre-column derivatization with 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl isothiocyanate (GITC) and N al pha-(2,4-dinitro-5-fluorophenyl)-L-alanine amide (Marfey's reagent, FDAA). The Chirobiotic T column was efficient in the separation of ring- and alpha -methyl-substituted phenylalanine analogues, but was ineffective for the am ides of these analogues. The Crownpak CR(+) column separated the ring-subst ituted phenylalanines and amides, whereas the alpha-methylated analogues we re coeluted. Of the two indirect methods, GITC derivatization seemed more e ffective than FDAA derivatization. (C) 2000 Elsevier Science B.V. All right s reserved.