Achiral deuterated derivatizing agent for enantiomeric analysis of carboxylic acids by NMR in a chiral liquid crystalline solvent

The use of a deuterated ‘probe’ for the enantiomeric analysis of chiral carboxylic acids is proposed. The probe is the perdeuterobenzyl fragment which can be easily attached to the acid and removed from the corresponding ester. The analysis is performed through the measurement of the proton-decoupled deuterium NMR spectrum of the chiral benzyl ester dissolved in poly-γ-benzyl-l-glutamate/dimethylformamide liquid crystal. Enantiomeric discrimination was observed for all the studied compounds on the para and/or α deuterons. There is no need for the deuterons to be located close to the stereogenic centre. Thus enantiomers were correctly distinguished from the signal of a deuterium located 12 bonds away from the asymmetric carbon. The major interest of this general technique is that no kinetic resolution should occur during the derivatization process.