NMR Studies of Drugs. Achiral and Chiral Lanthanide Shift Reagents with Mephenoxalone, a Substituted 2-Oxazolidinone

The 1H NMR spectra of the skeletal muscle relaxant, mephenoxalone, 1, 5-[(2-methoxyphenoxy) - methyl]-2-oxazolidinone, have been studied at 200 MHz in CDCl3 solution at 20° in the presence of the achiral lanthanide shift reagent, tris(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato) europium (III), 2, and the chiral reagent, tris[3-(heptafluoropropylhydroxymethylene)-(+)-camphorato]europium(III), 3. Both reagents 2 or 3 produced significant lanthanide induced shifts for spectral simplification suggesting major lanthanide binding at the carbonyl. With 3, enantiomeric shift differences were observed for the signals of the NH, OCH3, methine CHO, both protons of the CH2O and one proton of the CH2N, and the aryl proton H-6. Direct determinations of enantiomeric excess of samples of 1 appear feasible by use of 3.