Chiral recognition model for the resolution of ephedrine and related alpha,beta-aminoalcohols as enantiomeric oxazolidine derivatives.
The mechanism of chiral recognition has been investigated for a series of enantiomeric cis-oxazolidines on a commercially available high-performance liquid chromatographic chiral stationary phase (HPLC-CSP). The oxazolidine molecules were synthesized through the condensation of ephedrine and ephedrine-related molecules with aromatic aldehydes. The resulting molecules are rigid five-membered rings whose configuration has been determined by proton magnetic resonance and single-crystal X-ray diffraction. The oxazolidines derived from the condensation of ephedrine and aldehydes containing a pi-basic moiety such as naphthaldehyde were resolved on the HPLC-CSP as were those oxazolidines synthesized by using a pi-acidic aldehyde such as p-nitrobenzaldehyde. However, there was a reversal in the elution order for the two types of oxazolidines. Oxazolidines resulting from the condensation of ephedrine and a pi-neutral aldehyde such as benzaldehyde were not resolved. The results of this study suggest a chiral recognition model based on the formation of diastereomeric solute-CSP complexes through a single attractive interaction and chiral discrimination resulting from the difference in steric fit.
Wainer
I W
IW
Doyle
T D
TD
Fry
F S
FS
Hamidzadeh
Z
Z
D000605:Amino Alcohols / Q000032:analysis*; D004809:Ephedrine / Q000032:analysis*; D008956:Models, Chemical; D008968:Molecular Conformation; D010080:Oxazoles / Q000032:analysis*; D013237:Stereoisomerism
D000605:Amino Alcohols; D010080:Oxazoles; D004809:Ephedrine