Histamine-modified cationic beta-cyclodextrins as chiral selectors for theenantiomeric separation of hydroxy acids and carboxylic acids by capillaryelectrophoresis

Citation
G. Galaverna et al., Histamine-modified cationic beta-cyclodextrins as chiral selectors for theenantiomeric separation of hydroxy acids and carboxylic acids by capillaryelectrophoresis, ELECTROPHOR, 20(13), 1999, pp. 2619-2629
Citations number
53
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Chemistry & Analysis
Journal title
ELECTROPHORESIS
ISSN journal
0173-0835 → ACNP
Volume
20
Issue
13
Year of publication
1999
Pages
2619 - 2629
Database
ISI
SICI code
0173-0835(199909)20:13<2619:HCBACS>2.0.ZU;2-Y
Abstract
The enantiomeric separation of alpha-hydroxy acids and carboxylic acids was successfully performed by using 6-deoxy-6-N-histamino-beta-cyclodextrin (C D-hm), a monosubstituted positively charged beta-cyclodextrin (beta-CD) bea ring a histamine moiety linked to the C-6 Of a glucose unit in the upper CD rim via the amino group. Good results were obtained at a low selector conc entration (1 mm). The number of positive charges on the upper rim may be mo dulated as a function of pH, because of the different pK(a) of the amino an d the imidazolyl groups, and was found to affect both the enantioselectivit y and resolution factors. With the analogous 6-deoxy-[4-(2-aminoethyl)imida zolyl]-beta-cyclodextrin (CD-mh) bearing the histamine moiety linked to the C-6 via the imidazolyl group, very poor results were obtained, showing tha t the proximity of the positive charge to the cavity plays an important rol e in the enantiomeric recognition. The complexation mode was studied by ele ctrospray ionization-mass spectrometry (ESI-MS) and two-dimensional nuclear magnetic resonance (2-D NMR) ROESY experiments: the recognition model is c onsistent with an inclusion complexation of the aromatic ring of the analyt e within the CD cavity coupled to electrostatic interactions between the ca rboxylate and the protonated amino group of the cyclodextrin.