Mechanisms of enantiomeric resolution in cyclodextrin‐modified capillary electrophoretic separations of binaphthyl compounds

Abstract

The enantiomers of 1, 1'-bi-Bnaphthol, 1, 1'-binaphthyl diyl hydrogen phosphate, and 1 , l '-binaphthyldicarboxylic acid are separated using capillary electrophoresis with cyclodextrins added to the running buffer. It is demonstrated that the type and concentration of cyclodextrin employed are critical for maximum enantiomeric resolution. A modified version of a previously described model of enantiomeric separations in capluary electrophoresis is shown to support the observed separation behavior. Molecular modeling is employed to calculate interaction energies between the various enantiomers and cyclodextrins. A reasonable correlation between these computationally derived interaction energies and separation behavior resulted from a statistical mechanical treatment of the molecular modeling data. The importance of hydrogen bonding in inclusion complex formation was probed and the effects of minimization and solvation in molecular modeling calculations are also discussed.0 1995 Wdey-Liss, Inc.

About the role of enantioselective selector–selectand interactions and the mobilities of diastereomeric associates in enantiomer separations using CE

“…In contrast to the above-mentioned assumption regarding the equality of the mobilities of temporary diastereomeric associates, few earlier studies indicated that the mobilities of the diastereomeric associates of two enantiomers with the chiral selector were not always equal [15][16][17][18]. In 1997 a theoretical assumption was made that the enantiomers could be resolved by CE even when the association constants of two enantiomers with the chiral selector were the same (K R 5 K S 5 K) [5].…”

Chiral capillary electrophoresis: Facts and fiction on the reproducibility of resolution with randomly substituted cyclodextrins

“…The BNP-CD complex was extensively studied by the groups of Blaschke [11,12] and Kano [13][14][15]. The enantiomers were separated with various CDs, e.g., native [16,17] and sulfated CDs [18], heptakis(6-hydroxyethylamino-6-deoxy)-b-CD [19], maleic acid derivative of b-CD [20], CDs in combination with bile salts [21,22], and quaternary ammonium b-CDs in nonaqueous CE [23]. Separation was also performed with noncyclic saccharides, such as mono- [24], di- [25] and polysaccharides [26,27].…”

Chiral Recognition and Enantioseparation Mechanisms in Capillary Electrokinetic Chromatography

“…In the early 1990s, several studies on the computation of selector-selectand interactions in chiral CE [230][231][232] and other separation techniques were published [233][234][235]. This relates basically to the interactions between CDs and their chiral guests which seem to be caused by the fact that CDs are rather rigid molecules of medium size and therefore calculations for these molecules are easier, faster, and may be precise.…”