SummaryNew p-and y-cyclodextrin derivatives, selectively substituted with n-pentyl and methyl groups, e.g. heptakis(2,6-di-Omethyl-3-O-pentyl)-~-cyclodextrin, octakis(2-O-methyl-3,6-di-0-penty1)-y-cyclodextrin, and octakis(2,6-di-O-methyl-3-0-penty1)-y-cyclodextrin, have been prepared from specifically protected intermediates.The new cyclodextrin derivatives exhibit unique enantioselectivity towards important chiral constituents of essential oils. The enantiomers of lavandulol, abisabolol, nerolidol, and other terpenoid alcohols could be resolved and their presence in different essential oils could be proved. Methyl jasmonate and epi-methyl jasmonate could, in addition, be detected in jasmine concrete by two-dimensional gas chromatography. The enantiomers of the macrocyclic ketone muscone have been separated for the first time.

Vancomycin immobilized on silica served as the chiral stationary phase (CSP) in this investigation with polar organic solvents as the mobile phase in liquid chromatography (LC). It was shown that trace amounts of water were beneficial for improving peak shape and efficiency. To regulate the retention and selectivity an acid and/or base were added to the mobile phase where an excess of acid was shown to be preferential for enantioseparation. An unusual increase in selectivity with increasing temperature was shown for the acidic drug, thalidomide. Additionally, nonlinear van't Hoff plots were obtained for metoprolol enantiomers that showed increased retention with increasing temperature. Metoprolol also showed unusual behavior in the polar organic phase when water was added to resemble reversed-phase chromatography, with minimum retention observed at high water or high methanol concentrations. In both instances a high degree of electrostatic interaction between metoprolol and vancomycin was concluded. Metoprolol and ten of its analogs were examined on this CSP to evaluate the enantiorecognition process. A comparison in enantioselectivity for a number of acidic and basic drugs using this CSP was also carried out using the polar organic phase, reversed phase, and normal phase LC which were all compared to the results obtained in supercritical fluid chromatography (SFC). Polar organic phase LC offered a better separation of basic molecules while reversed phase LC was preferred for the resolution of acids. SFC showed the broadest enantioselectivity overall and normal phase LC indicated similar properties, as expected, to SFC but with lower column efficiency. Copyright 2000 Wiley-Liss, Inc.

No abstract

No abstract

Enantioselective gas chromatography Enantioselective supercritical fluid chromatography Immobilized chiral stationary phases Modified cyclodextrin SummaryHeptakis(2,6-di-Omethyl-3-Opentyl) (2-Omethyl-6-Ooct-1 -enyl-3-0-penty1)-y-cyclodextrin was immobilized to narrow-bore fused silica capillaries after selective modification. One tert-butyldimethylsilyl group was introduced into octakis-(2-O methyl-3-Opentyl)-ycyclodextrin in order to get a pure monofunctionalized cyclodextrin derivative. During synthesis the fert-butyldimethylsilyl group was replaced by an anchoring group to bind the cyclodextrin to a polysiloxane. After thermal immobilization of the modified polysiloxane this new chiral stationary phase was applied in GC and SFC. High efficiency separations were obtained in GC. In SFC very polar compounds could be chromatographed at low temperatures resulting in higher separation factors as compared to GC.