Determination of the enantiomeric purity of disubstituted β-lactams by NMR spectroscopy using a chiral shift reagent

✍ Scribed by J. Belleney; C. Bui; F. J. Carriere

• Publisher: John Wiley and Sons
• Year: 1990
• Tongue: English
• Weight: 481 KB
• Volume: 28
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1260280709

✦ Synopsis

Abstract

The enantiomeric purities of disubstituted β‐lactams were determined by ^1^H and ^13^C 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. ^13^C NMR spectroscopy is more advantageous than ^1^H NMR, which is of limited use owing, for example, to the significant line broadening observed in the ^1^H 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.