DETERMINATION OF THE ENANTIOMERIC PURITY OF DISUBSTITUTED BETA-LACTAMS BY NMR-SPECTROSCOPY USING A CHIRAL SHIFT-REAGENT

The enantiomeric purities of disubstituted β‐lactams were determined by 1H and 13C NMR spectroscopy using tris[3‐(trifluoromethylhydroxymethylene)‐d‐camphorato]europium(III), Eu(tfc)3, as a chiral shift reagent. Using a [Eu(tfc)3]/[lactam] ratio of 0.5, most of the resonances were split into signal pairs due to the respective enantiomers. The method gives quantitative enantiomeric compositions. 13C NMR spectroscopy is more advantageous than 1H NMR, which is of limited use owing, for example, to the significant line broadening observed in the 1H spectra at [Eu(tfc)3]/[lactam] > 0.8. Assignments of the proton and carbon signals were obtained for the two enantiomers of the complexed lactams. Copyright © 1990 John Wiley & Sons, Ltd.