Enantioselective anion exchangers based on cinchona alkaloid-derived carbamates: Influence of C8/C9 stereochemistry on chiral recognition
✍ Scribed by Norbert M. Maier; Lorenzo Nicoletti; Michael Lämmerhofer; Wolfgang Lindner
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 152 KB
- Volume
- 11
- Category
- Article
- ISSN
- 0899-0042
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✦ Synopsis
Four diastereomeric chiral stationary phases (CSPs) based on quinine, quinidine, epiquinine, and epiquinidine tert-butyl carbamate selectors were synthesized and evaluated under ion exchange HPLC conditions with a set of racemic N-acylated and N-oxycarbonylated alpha-amino acids as selectands. The enantioseparation potential of quinine- and quinidine-derived CSPs proved to be far superior to that of their C9-epimeric congeners. The absolute configuration of C9 stereogenic center of the cinchonan backbone of these selectors was identified as the structural feature controlling the elution order. Guided by an X-ray structure of a most favorable selector-selectand complex and the observed chromatographic enantioseparation data, a chiral recognition model was advanced. The contributions of ion-pairing, pi-pi donor-acceptor, hydrogen bonding and steric interactions were established as crucial factors.