engleski

Study of Chromatographic Enantioseparation of the Esters of N-Dinitrobenzoyl (N-DNB) and N-Benzoyl (N-B) a-Amino Acids on Novel Chiral Stationary Phases Containing Structurally Matching N-DNB and N-B-a-AA Amides in the Chiral Selector

Enantioseparation ability and enantiopreference of chiral stationary phases CSP 1-3, containing terminal N-3, 5-dinitrobenzoyl (N-DNB) unit, and CSP 4, containing terminal N-benzoyl (N-B) unit are studied. Separation factors (a) for the two sets of the test racemates (TR) that structurally match chiral selector of these CSPs is determined. The first set consists of seven N-DNB a-amino acid isopropylesters (TR 1A-7A), and the second one of their N-B analogues (TR 1-7). The best enantioseparation (aaverage 1.27) is obtained when p-acceptor DNB unit is present in both, TR and CSP. One p-acceptor unit, either in analyte or in CSP, suffices for efficient enantioseparation (aaverage 1.19). Interaction between p-neutral units in the CSP and test racemate does not afford effective enantioseparation (aaverage 1.03). Using (S)-enantiomers of all TRs as the standards with CD detection has revealed regular preference of the CSPs for the enantiomers containing amino acid amide of the same absolute configuration. The possible origin of such enantiopreference is discussed

p-p Interactions; Chiral stationary phases; Pirkle-type; Electron-deficient groups

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