AbstractThe enantiomeric purities of disubstituted β‐lactams were determined by1H and13C 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 than1H NMR, which is of limited use owing, for example, to the significant line broadening observed in the1H spectra at [Eu(tfc)3]/[lactam]>0.8. Assignments of the proton and carbon signals were obtained for the two enantiomers of the complexed