Comparative enantioseparations with native β-cyclodextrin and heptakis-(2-O-methyl- 3,6-di-O-sulfo)-β-cyclodextrin in capillary electrophoresis

Abstract

Twenty-three cationic chiral analytes were resolved in capillary electrophoresis using native beta-cyclodextrin and single isomer heptakis-(2-O-methyl-3,6-di-O-sulfo)-beta-cyclodextrin as chiral selectors. For 12 of 16 chiral analytes resolved with both chiral selectors the enantiomer migration order was opposite. In selected cases the structure of cyclodextrin-analyte complexes in aqueous solution was investigated using one-dimensional transverse rotating frame nuclear Overhauser and exchange spectroscopy. It was found that in contrast to mainly inclusion-type complexes between chiral analytes and beta-cyclodextrin, external complexes are formed between the chiral analytes and structurally crowded, highly charged heptakis-(2-O-methyl-3,6-di-O-sulfo)-beta-cyclodextrin.

Chiral electromigration techniques in pharmaceutical and biomedical analysis

“…In the case of derivatized CDs additional interactions such as ionic interactions for CDs bearing charged substitutents have to be considered as well. In fact it has been demonstrated that the formation of an inclusion complex is not a prerequisite for the stereospecific recognition of analyte enantiomers by a CD [42,43]. Within the many techniques applied to study the structures of CD-analyte complexes NMR has significantly contributed [44][45][46].…”

Separation of vinca alkaloid enantiomers by capillary electrophoresis applying cyclodextrin derivatives and characterization of cyclodextrin complexes by nuclear magnetic resonance spectroscopy

“…This additional complex forming possibility may explain the higher stability of the Looking for the structural and chemical reasons of the enantiomer migration order (EMO) i.e., finding the relationships between the structure of a chiral selector, chiral analyte and analyte-selector complex on the one hand, and the EMO on the other hand, may provide important information regarding the nature of intermolecular forces involved in complex formation and enantioselective recognition of analytes by chiral selectors. In the literature several examples were reported on information regarding the involvement of different parts of an analyte in the intermolecular complex formation with CDs [25][26][27]34,35,47,48]. These data may explain the change of molecular recognition of the analytes.…”

Pharmaceutical and biomedical applications of chiral capillary electrophoresis and capillary electrochromatography: An update

“…Chankvetadze et al [60] observed opposite enantiomer migration order for 12 out of 16 basic analytes separated by b-CD and heptakis-…”