Development, Characterization And Application Of Chiral Stationary Phases

Abstract

Cyclofructans are cyclic oligosaccharides consisting of a crown ether core with pendent fructofuranose units. These unique macrocycles were reported recently to be powerful chiral selectors. Native cyclofructans show little enantioselectivity. However, when they are derivatized and bonded to silica, they make excellent chiral selectors for HPLC. In this study, several new derivatives of cyclofructan 6 were prepared by introducing aromatic selectors with electron-withdrawing chloro and nitro group(s) and electron-donating methyl group. Their enantioselectivities were evaluated in the normal phase mode in comparison to the commercially available cyclofructan columns (LARIHC CF6-P, LARIHC CF6-RN and LARIHC CF7-DMP). In several cases, the new columns showed improved enantioselectivity compared to the existing commercially available stationary phases. Furthermore, an evaluation of the number and position of chloro and methyl groups on the phenyl derivatizing agent is discussed in terms of their ability to alter enantioselectivity. For the other project, high-performance liquid chromatographic and gas chromatographic methods were developed for the separation of enantiomers of twelve novel aziridines. The separations were performed on cyclodextrin, cyclofructan, amylose, cellulose and macrocyclic-glycopeptide based chiral stationary phases. The amylose based chiral stationary showed good selectivity toward the aziridines while having low capacity factors. It was also shown that the high-performance liquid chromatography provided improved separations compared to gas chromatography. Effective separations for ten aziridines were developed.