Resolution of non-racemic mixtures in achiral chromatographic systems: A model for, the enantioselective effects observed

Gil‐Av, E.; Schurig, Volker

doi:10.1016/0021-9673(94)80413-3

Cited by 40 publications

(13 citation statements)

References 10 publications

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“…95,107,108 The phenomenon has been treated theoretically assuming molecular association of the enantiomers to homo-and heterochiral dimers. 109,110 The dimerization equilibria and phase-distribution behavior of diastereomeric dimers determine whether the pure enantiomer is eluted before or after the racemate. An intermediate situation between (i) the differential elution of the excess enantiomer and the racemic mixture on the achiral stationary phase and (ii) the differential elution of single enantiomers on chiral stationary phase has been considered in the following thought experiment: 111 when the excess enantiomer (R) is eluted before the racemate (R, S) on an achiral stationary phase, the addition of a chiral selector to the achiral stationary phase will cause the separation of the racemic fraction into (R) and (S) enantiomers.…”

Section: Separation Of a Nonracemic Mixture Into Excess Enantiomer Anmentioning

confidence: 99%

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: Separation Of a Nonracemic Mixture Into Excess Enantiomer Anmentioning

confidence: 99%

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

Schurig

2005

Chirality

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“…). Mostly though, it is only the first eluted portion that can be obtained essentially free of the second eluted portion in practice and in accord with the theory , which dictates that obtaining fractions of the first eluted portion completely free of the second eluted portion is possible. Note that complete separation of the ee and racemic portions is not possible due to the dynamic equilibrium that is in effect and at least some fractionated material will remain nonracemic even under the most optimal conditions.…”

Section: Mplc Versus Gravity‐driven Column Chromatography For N‐acetymentioning

confidence: 97%

The self‐disproportionation of enantiomers (SDE): The effect of scaling down, potential problems versus prospective applications, possible new occurrences, and unrealized opportunities?

et al. 2019

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This commentary discusses an important, though not widely appreciated, chiral phenomenon of molecular chirality that effectively always occurs whenever nonracemic samples are subjected to practically any physicochemical process (e.g., force field, recrystallization, sublimation, even distillation, etc.) under totally achiral conditions external to the sample itself. The phenomenon is termed as the self‐disproportionation of enantiomers (SDE) and though ubiquitous, its presence may not always be readily apparent, or workers may be otherwise oblivious to its effects. In the particular case of chromatography, when the SDE is apparent, the enantiomeric excess (ee) of the chiral compound is observed to vary across an eluted peak, with anterior eluted portions either enantioenriched or enantiodepleted relative to the ee of the starting material, and conversely for the posterior eluted portions. Herein, we highlight various aspects of the SDE phenomenon as it pertains to chromatography and, in particular, the effect of scaling down chromatographic systems, the potential risk of problems that the SDE can cause, as well as opportunities for practical applications of the phenomenon, possible new occurrences of the SDE phenomenon to be searched for, and unrealized opportunities.

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“…As the dimers represent diastereomers, they possess different retention factors. One of the models for the enantioselective EE ‐effect observed was developed by Gil‐Av . Recent calculations even implied that the unusual elution order RSR (or SRS ) of enantiomers may arise within a unresolved peak when an achiral stationary phase is doped with a small amount of a nonracemic selector …”

Section: The Separation Of Nonracemic Mixtures In Achiral Chromatogramentioning

confidence: 99%

On the Centenary of Emanuel Gil‐Av, Former Professor of the Weizmann Institute of Science and Pioneer of Enantioselective Chromatography

Schurig

2016

Israel Journal of Chemistry

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Emanuel Gil‐Av (Zimkin) was born in 1916 and passed away in 1996. The introduction of chemical selectivity into the chromatographic separation process constitutes his main scientific contribution. This approach culminated in the first enantiomeric separation of racemic amino acids by gas chromatography on an optically active chiral stationary phase in 1966, together with Binyamin Feibush and Rosita Charles‐Sigler. Thus the year 2016 marks an important date to remember and to appreciate the invaluable achievements of Gil‐Av in the realm of chirality carried out at the Weizmann Institute of Science, Israel.

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Resolution of non-racemic mixtures in achiral chromatographic systems: A model for, the enantioselective effects observed

Cited by 40 publications

References 10 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

The self‐disproportionation of enantiomers (SDE): The effect of scaling down, potential problems versus prospective applications, possible new occurrences, and unrealized opportunities?

On the Centenary of Emanuel Gil‐Av, Former Professor of the Weizmann Institute of Science and Pioneer of Enantioselective Chromatography

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