Extraordinary chiral discrimination in inclusion gas chromatography. Thermodynamics of enantioselectivity between a racemic perfluorodiether and a modified γ-cyclodextrin

Schurig, Volker; Schmidt, R.

doi:10.1016/s0021-9673(03)00180-8

Cited by 39 publications

(51 citation statements)

References 43 publications

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“…18, bottom left). 97 The determination of thermodynamics of enantioselectivity via the concept of the retention-increment RV (vida supra) furnished the largest data for chiral discrimination ever reported in enantioselective GC: If ''compound B'' were not a characteristic degradation product of sevoflurane, its extraordinary propensity for strong chiral bias would have escaped attention as such a structure would hardly be conceived by mere intuition. This highly enantioselective system constitutes not only an ideal target for future systematic studies of throughput in preparative-scale GC, including chiral SMB technology, but also for theoretical studies on mechanisms of chiral recognition.…”

Section: Observation Of An Unprecedentedly High Enantioselectivity Inmentioning

confidence: 99%

“…In this respect the unexpected observation that the exceedingly high separation factor a = 9.7 as found on g-Lipodex E at ambient temperature (30jC) was reduced to a = 2.1 on b-Lipodex E and vanished 98 completely with a = 1 on a-Lipodex E (at 30jC each) calls for a reasonable explanation in the future. 97 The isolated enantiomers of ''compound B'' were utilized for enantiomeric discrimination studies by various chiral sensor devices modified with Lipodex E 7: (i) thickness shear mode resonators (TSMR), (ii) surface acoustic wave (AW) sensors, (iii) surface plasmon resonance (SPR) sensors, and (iv) reflectometric interference spectroscopy (RIfS) sensors. 98 A striking example for the high enantioselectivity of an SPR device is depicted in Figure 18, bottom right.…”

Section: Observation Of An Unprecedentedly High Enantioselectivity Inmentioning

confidence: 99%

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Contributions to the theory and practice of the chromatographic separation of enantiomers

Schurig

2005

Chirality

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The theory and practice of enantioselective capillary chromatography employing metal coordination compounds and modified cyclodextrins as chiral stationary phases are treated. A unified approach involving all contemporary chromatographic methods and a single enantioselective column is described. Reliable thermodynamic data of enantioselectivity are derived by the retention-increment method. The existence of an isoenantioselective temperature is demonstrated. Kinetic enantiomerization studies are presented. The preparative-scale separation of enantiomers by gas chromatography with enantioselective packed columns is achieved. Unusual phenomena and future aspects of enantioselective chromatography are discussed.

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Section: Observation Of An Unprecedentedly High Enantioselectivity Inmentioning

confidence: 99%

Section: Observation Of An Unprecedentedly High Enantioselectivity Inmentioning

confidence: 99%

Contributions to the theory and practice of the chromatographic separation of enantiomers

Schurig

2005

Chirality

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“…3,51 For this approach a reference column containing the pure solvent, in order to determine achiral contributions to retention, and an inert reference standard, usually an n-alkane which does not interact with the selector, is required. Unfortunately no inert reference standard can be conceived for cyclodextrin selectors since, as shown in this work, alkanes selectively interact with cyclodextrins (otherwise enantioselectivity could not be observed).…”

Section: Mechanistic Considerationsmentioning

confidence: 99%

Gas chromatographic enantioseparation of unfunctionalized chiral alkanes: A challenge in separation science (overview, state of the art, and perspectives)

et al. 2008

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The chromatographic enantioseparation of small unfunctionalized chiral alkanes C*HR(1)R(2)R(3) (R = alkyl) represents a challenge in separation science. Because of the lack of any functional groups, enantiorecognition in the presence of a chiral selector is solely based upon weak enantioselective Van der Waals forces. Racemic alkanes containing seven and eight carbon atoms, i.e. 3-methylhexane (C7), 2,3-dimethylpentane (C7), 3-methylheptane (C8), 3,4-dimethylhexane (C8), 2,4-dimethylhexane (C8), 2,3-dimethylhexane (C8), and 2,2,3-trimethylpentane (C8) have been gas chromatographically enantioseparated on different modified cyclodextrins. The substitution pattern and cavity size of the cyclodextrin selectors have a pronounced effect on the degree of enantiorecognition observed. Thermodynamic parameters of enantiorecognition between four chiral alkanes and octakis(6-O-methyl-2,3-di-O-pentyl)-gamma-cyclodextrin (Lipodex G) have been determined. The possible role of molecular inclusion is indicated by the complete loss of enantioselectivity when the cyclodextrins are replaced by the corresponding linear dextrins ("acyclodextrins"). The enantioseparations of all seven chiral C7-C8 alkanes, six of them simultaneously, has been achieved on mixed binary selector systems whereby two different modified cyclodextrins are present in one gas chromatographic column. The smallest chiral (nonisotopically labeled) allene, i.e., 2,3-pentadiene, has been resolved gas chromatographically on a cyclodextrin selector.

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“…Moreover, enantioselective and nonenantioselective contribution to the retention must be considered. 29 Finally, the enantioseparation factor a is temperature-dependent and therefore undefined in temperature-programmed chromatographic runs. Still, qualitatively matched and mismatched cases can readily be observed in Figures 9 -12, which represent temperature-programmed enantiomeric separations of selected derivatized amino acids on the four CSPs.…”

Section: Observation Of Matched and Mismatched Enantioselectivitiesmentioning

confidence: 99%

Combining the enantioselectivity of a cyclodextrin and a diamide selector in a mixed binary gas‐chromatographic chiral stationary phase

2005

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The present work reports on the investigation of a mixed binary chiral stationary phase (CSP) prepared by simultaneous attachment of permethylated-bcyclodextrin (D selector) and resorcinarene with pendant L -or D-valine diamide groups (LV and DV selectors, respectively) to a polysiloxane matrix via platinum-catalyzed hydrosilylation. The gas-chromatographic investigation of a number of racemates on the four different CSPs (D, DV, DDV, and DLV) showed that the enantioselectivity of the individual chiral selectors was retained in the mixed binary CSPs. As a consequence, hydrocarbons, underivatized alcohols, ketones, and almost all proteinogenic amino acid derivatives could be separated simultaneously on each of the mixed CSPs. Matched and mismatched cases of enantioseparation on the mixed binary CSPs were observed but turned out to be of minor importance for enantiomeric separation. In general, more racemates were separated with a z 1.02 on the mixed phases as compared to the single phases. In order to analyze the influence of the presence of the diamide selector on the enantioselectivity of the cyclodextrin selector, a mixed ternary CSP containing the selector D and a racemic mixture of the selectors DV and LV [D(DVLV)] was prepared and investigated. Merits and limitations of the approach of mixed binary CSPs are discussed.

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Extraordinary chiral discrimination in inclusion gas chromatography. Thermodynamics of enantioselectivity between a racemic perfluorodiether and a modified γ-cyclodextrin

Cited by 39 publications

References 43 publications

Contributions to the theory and practice of the chromatographic separation of enantiomers

Contributions to the theory and practice of the chromatographic separation of enantiomers

Gas chromatographic enantioseparation of unfunctionalized chiral alkanes: A challenge in separation science (overview, state of the art, and perspectives)

Combining the enantioselectivity of a cyclodextrin and a diamide selector in a mixed binary gas‐chromatographic chiral stationary phase

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