Enantioselective anion exchangers based on cinchona alkaloid-derived carbamates: influence of C8/C9 stereochemistry on chiral recognition.
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.
Maier
N M
NM
Institute of Analytical Chemistry, University of Vienna, Vienna, Austria.
Nicoletti
L
L
Lämmerhofer
M
M
Lindner
W
W
D000962:Antimalarials / Q000737:chemistry; D002219:Carbamates / Q000737:chemistry / Q000302:isolation & purification; D002851:Chromatography, High Pressure Liquid; D002930:Cinchona Alkaloids / Q000737:chemistry* / Q000302:isolation & purification; D018360:Crystallography, X-Ray; D008956:Models, Chemical; D008968:Molecular Conformation; D011802:Quinidine / Q000031:analogs & derivatives / Q000737:chemistry; D011803:Quinine / Q000031:analogs & derivatives / Q000737:chemistry; D013237:Stereoisomerism
D000962:Antimalarials; D002219:Carbamates; D002930:Cinchona Alkaloids; D011803:Quinine; D011802:Quinidine