title: NMR determination of enantiomers of 7-chloro-3,3a-dihydro-2-methyl-2H,9H-isoxazolo(3,2-b)(1,3)benzoxazin-9-one using chiral shift reagent, tris(3-(heptafluorobutyryl)-d-camphorato)europium(III).
abstract: A simple NMR method was developed for the determination of the enantiomers of 7-chloro-3,3a-dihydro-2-methyl-2H,9H-isoxazolo[3,2-b][1,3]benzoxazin-9-one. Chiral shift reagent, tris[3-(heptafluoroburyryl)-d-camphorato]europium(III), causes the doublet assigned to the protons of the 2-methyl group, which normally appears at about 1.5 ppm, to split into two pairs of doublets and to shift downfield to about 2.0-3.5 ppm. The downfield pair of doublets represents the two enantiomers present in one racemate, designated as the beta-form, while the upfield pair represents the enantiomers of the racemate designated as the alpha-form. From the integration of the area under the doublets, the relative concentration of all four enantiomers was determined.
mesh_terms: D005063:Europium; D007555:Isoxazoles / Q000032:analysis*; D009682:Magnetic Resonance Spectroscopy; D008722:Methods; D010078:Oxazines / Q000032:analysis*; D010080:Oxazoles / Q000032:analysis*
chemical_list: D007555:Isoxazoles; D010078:Oxazines; D010080:Oxazoles; D005063:Europium