ISSN:
0018-019X
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
An optically active molecular cleft incorporating a 9,9′-spirobi[9H-fluorene] spacer and two N-(5,7-dimethyl-1,8-naphthyridin-2-yl)carboxamide: (CONH(naphthyr)) moieties as H-bonding sites was covalently bound to silica gel to provide the new chiral stationary phase (CSP) (R)-16 (Scheme 2). Previous solution-binding studies in CDCl3 had shown that the anchored molecular cleft was capable of complexing optically active dicarboxylic acids with differences in free energy of the formed diastereoisomeric complexes (Δ(ΔG0)) between 0.5 and 1.6 kcal mol-1 (T = 300 K). The optical resolution of racemic dicarboxylic acids, that are bound with a high degree of enantioselectivity in the liquid phase, was now achieved by HPLC on the CSP (R)-16. The order of enantiomer elution was as predicted from the solution studies, and the separation factor α varied between 1.18 and 1.24. A series of 1,1′-binaphthalene-2,2′-diol derivatives were also resolved on the new CSP, in some cases with baseline separation. The order of enantiomer elution under normal-phase chromatographic conditions was rationalized by computer modeling of the association between the solute enantiomers and the immobilized molecular cleft. HPLC Separations with eluents of different polarity suggested that the attractive interactions between solute and immobilized chiral selector are a combination of H-bonding, which prevails in apolar eluents, and aromatic π--π stacking, which dominates in polar eluents.
Additional Material:
3 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/hlca.19970800323
