Direct chiral separation of tryptophan analogues using heptakis(3-O-methyl)-β-cyclodextrin-bonded stationary phase in reversed-phase liquid chromatography

For the direct separation of racemic tryptophan analogues by reversed-phase liquid chromatography, native beta-cyclodextrin (CD), heptakis(3-O-methyl)-beta-CD, and heptakis(2,3-di-O-methyl)-beta-CD chiral stationary phases were examined. Direct separation of various tryptophan analogues was accomplished with heptakis(3-O-methyl)-beta-CD stationary phase. It was observed that the position of substituents affects retention and enantioselectivity of tryptophan analogues. Substitution at the 6-position (e.g., 6-methyl-DL-tryptophan and 6-fluoro-DL-tryptophan) significantly increased retention and enantioselectivity. (C) 1999 Academic Press.