Characterization of a chiral stationary phase by HR/MAS NMR spectroscopy and investigation of enantioselective interaction with chiral ligates by transferred NOE.
The surface chemistry of a chiral stationary phase (CSP) with a (tert-butyl carbamoyl) quinine selector immobilized on thiol-modified silica has been characterized by (1)H HR/MAS NMR and (29)Si CP/MAS NMR spectroscopy. The mostly well-resolved (1)H signals could be assigned to stem from the surface-bound selector and the latter suggested a bi- and trifunctional silane linkage. Suspended-state NMR spectroscopy thus proved a well-characterized surface chemistry as proposed. To study chiral recognition phenomena in the presence of the CSP, (1)H HR/MAS 2D transfer NOESY investigations in methanol-d(4) have been undertaken with various solutes including N-3,5-dinitrobenzoyl derivatives of leucine (DNB-Leu) and N-acetyl phenylalanine (Ac-Phe). Both (R)- and (S)-enantiomers of DNB-Leu and Ac-Phe interacted with the tBuCQN-CSP as indicated by negative cross-peaks in the trNOESY spectra, while the 2D NOESY of the dissolved solutes in absence of the chiral stationary phase showed positive cross-peaks. The intensities of the trNOE cross-peaks were much stronger for the (S)-enantiomers. This stereoselectivity paralleled the experimental chromatographic behavior, where the (S)-enantiomers revealed stronger binding and retention on the tBuCQN-CSP as well. Hence, we were able to correlate the retention behavior to the trNOE NMR spectroscopic data in a qualitative manner.
Hellriegel
Christine
C
Institute of Organic Chemistry, University of Tübingen, Auf der Morgenstelle 18, 72076 Tübingen, Germany.
Skogsberg
Urban
U
Albert
Klaus
K
Lämmerhofer
Michael
M
Maier
Norbert M
NM
Lindner
Wolfgang
W
D002851:Chromatography, High Pressure Liquid; D004136:Dinitrobenzenes / Q000737:chemistry* / Q000302:isolation & purification; D007930:Leucine / Q000031:analogs & derivatives* / Q000737:chemistry* / Q000302:isolation & purification; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular; D010649:Phenylalanine / Q000031:analogs & derivatives* / Q000737:chemistry* / Q000302:isolation & purification; D011803:Quinine / Q000737:chemistry; D013237:Stereoisomerism
D004136:Dinitrobenzenes; C465293:dinitrobenzoyl leucine; D010649:Phenylalanine; D011803:Quinine; D007930:Leucine; C044228:N-acetylphenylalanine