Enantioselective complexation of carbamoylated quinine and quinidine with <Emphasis Type="Italic">N</Emphasis>-blocked amino acids: vibrational and electronic circular dichroism study |
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Authors: | Ond?ej Julínek Marie Urbanová Wolfgang Lindner |
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Institution: | Department of Analytical Chemistry, Institute of Chemical Technology, Technická 5, 166 28, Prague, Czech Republic. |
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Abstract: | Infrared absorption (IR) and vibrational and electronic circular dichroism (VCD and ECD, respectively) spectra of tert-butylcarbamoylquinine (t-BuCQN) and pseudoenantiomeric tert-butylcarbamoylquinidine (t-BuCQD), denoted as selectors (SO), complexed with chiral (S) and (R)-3,5-dinitrobenzoylleucine (DNB-Leu) and achiral 3,5-dinitrobenzoylglycine (DNB-Gly), denoted as selectands (SA), in methanol
and acetonitrile, with the spectra of pure SA and SO are reported. H–D exchange of exchangeable hydrogen atoms of SA and SO
in deuterated methanol which occurs in IR and VCD experiments is exploited to identify Amide II and Amide III vibrational
modes. The formation of preferentially bound complexes composed of sterically compatible combinations of DNB-Leu and SO are
manifested by increased intensity of VCD bands assigned to vibrations of amide, carbamate, quinoline, and dissociated carboxylate
group and also by increased ECD signals. The VCD technique revealed similarities between the strongly bound diastereomeric
complex of chiral DNB-Leu and SO and the complex of achiral DNB-Gly and SO, highlighting the leading role of SO in the formation
of SA–SO complex.
Figure Vibrational circular dichroism study: Interaction markers typical of the binding between the quinine selector and the derivatized
amino acid selectand |
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Keywords: | Diastereomeric complexes Quinine derivatives N-Derivatized amino acids DNB derivatives Vibrational circular dichroism Electronic circular dichroism |
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