A convenient, NMR-based method for the analysis of diastereomeric mixtures of pseudoephedrine amides.
Amides of pseudoephedrine and ephedrine are shown to undergo highly stereospecific, invertive cyclization to form 4,5-dihydro-3,4-dimethyl-5-phenyl-1,3-oxazolium triflate derivatives in the presence of triflic anhydride-pyridine. 1H NMR spectra of the unpurified reaction products are remarkably clean, with sharp, well-defined peaks, and allow for rapid assessment of the diastereomeric purities of the starting amides. [reaction: see text].
Chain
William J
WJ
Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA.
Myers
Andrew G
AG
D000577:Amides / Q000032:analysis* / Q000737:chemistry*; D003500:Cyclization; D004809:Ephedrine / Q000031:analogs & derivatives / Q000032:analysis* / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods* / Q000592:standards; D008968:Molecular Conformation; D010080:Oxazoles / Q000138:chemical synthesis / Q000737:chemistry; D012015:Reference Standards; D012680:Sensitivity and Specificity; D013237:Stereoisomerism
D000577:Amides; D010080:Oxazoles; D004809:Ephedrine