Stereoselectivity in bis(α-amino acid) copper(II) complexes—VII

Kurganov, A. A.; Zhuchkova, L.Ya.; Davankov, V. A.

doi:10.1016/0022-1902(78)80513-2

Cited by 17 publications

(2 citation statements)

References 3 publications

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“…76 Pirkle deemed these interactions insufficient for chiral recognition, since either enantiomer should be able to afford both hydrogen bonds simultaneously with the CSP. He instead proposed a x-dipole stacking of the amides of CSP 10 and analyte (Figure 6) which, because it is a face-to-face Dipole-stacking model Figure 6. Hydrogen bonding versus dipole stacking for chiral recognition of iV-acyl-a-amino amides on CSP 10.…”

Section: Donor-acceptor Cspsmentioning

confidence: 99%

Considerations of chiral recognition relevant to the liquid chromatography separation of enantiomers

Pirkle¹,

Pochapsky²

1989

Chem. Rev.

874

375

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Section: Donor-acceptor Cspsmentioning

confidence: 99%

Considerations of chiral recognition relevant to the liquid chromatography separation of enantiomers

Pirkle¹,

Pochapsky²

1989

Chem. Rev.

874

375

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“…The existence of T iso in enantioselective liquid chromatography was predicted in 1978 by Davankov et al and in enantioselective gas chromatography in 1984 by Koppenhoefer and Bayer . First examples were independently observed by Musso et al in liquid chromatography, by Gil-Av et al in hydrogen-bonding GC systems, and by Schurig et al in complexation GC (a report of peak inversion for methyl lactate on a modified cyclodextrin selector (Lipodex E) could not be reproduced in our hands).…”

mentioning

confidence: 74%

Temperature-Induced Inversion of the Elution Order of Enantiomers in Gas Chromatography: N-Ethoxycarbonyl Propylamides and N-Trifluoroacetyl Ethyl Esters of α-Amino Acids on Chirasil-Val-C₁₁ and Chirasil-Dex Stationary Phases

2007

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Inversion of the elution order of enantiomers caused by enthalpy-entropy compensation at the isoenantioselective temperature (Tiso) was experimentally observed by gas chromatography on the diamide-type chiral stationary phase (CSP), Chirasil-L-Val-C11, with N-ethoxycarbonyl propylamide (ECPA) derivatives of a number of alpha-amino acids. For the first time, a clear visual representation of the increase of the apparent enantioseparation factor alpha app from 1.00 to 1.08 as the temperature is raised from 120 to 170 degrees C is presented. The increase of alpha app is accompanied by a concomitant reduction of the retention factors of the enantiomers. The Tiso values were in the range from 110 to 130 degrees C depending on the nature of the alpha-amino acid. On the contrary, the Tiso values of the N(O)-trifluoroacetyl ethyl ester derivatives (TFA-Et) of the same alpha-amino acids were approximately 80 degrees higher than that of ECPA derivatives. The comprehensive thermodynamic investigation of the enantioseparation of ECPA and TFA-Et derivatives of valine and alanine using the retention increment method showed that the Delta L,D(DeltaH) difference between the diastereomeric selector-selectand associates was almost the same for ECPA and TFA-Et derivatives despite a much stronger bonded selector-selectand association taking place for the ECPA derivatives. On the other hand, the Delta L,D(DeltaS) values were found to be more negative in the case of ECPA derivatives, resulting in the unusually low values of Tiso. A temperature-dependent inversion of the elution order of enantiomers was also observed on the cyclodextrin-type CSP, Chirasil-Dex, with TFA-Et derivatives of several alpha-amino acids. The Tiso values were in the range from 20 to 170 degrees C depending on the nature of the alpha-amino acid. The results obtained demonstrate the necessity to conduct temperature-dependent studies in order to optimize the enantiomeric separation of single racemates isothermally or of mixtures of racemates in temperature-programmed runs using enantioselective GC. It is also shown that consideration of the elution order of enantiomers and the value of the apparent enantioseparation factor alpha app alone, without performing temperature-dependent measurements, can easily lead to wrong conclusions regarding the enantiorecognition mechanism.

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The nature of chiral recognition: Is it a three-point interaction?

1997

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Stereoselectivity in bis(α-amino acid) copper(II) complexes—VII

Cited by 17 publications

References 3 publications

Considerations of chiral recognition relevant to the liquid chromatography separation of enantiomers

Considerations of chiral recognition relevant to the liquid chromatography separation of enantiomers

Temperature-Induced Inversion of the Elution Order of Enantiomers in Gas Chromatography: N-Ethoxycarbonyl Propylamides and N-Trifluoroacetyl Ethyl Esters of α-Amino Acids on Chirasil-Val-C₁₁ and Chirasil-Dex Stationary Phases

The nature of chiral recognition: Is it a three-point interaction?

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Stereoselectivity in bis(α-amino acid) copper(II) complexes—VII

Cited by 17 publications

References 3 publications

Considerations of chiral recognition relevant to the liquid chromatography separation of enantiomers

Considerations of chiral recognition relevant to the liquid chromatography separation of enantiomers

Temperature-Induced Inversion of the Elution Order of Enantiomers in Gas Chromatography: N-Ethoxycarbonyl Propylamides and N-Trifluoroacetyl Ethyl Esters of α-Amino Acids on Chirasil-Val-C11 and Chirasil-Dex Stationary Phases

The nature of chiral recognition: Is it a three-point interaction?

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Product

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Temperature-Induced Inversion of the Elution Order of Enantiomers in Gas Chromatography: N-Ethoxycarbonyl Propylamides and N-Trifluoroacetyl Ethyl Esters of α-Amino Acids on Chirasil-Val-C₁₁ and Chirasil-Dex Stationary Phases