Paper
Diastereomers of the insect repellent 3-acetyl-2-(2′,6′-dimethyl-5′-heptenyl)oxazolidine. Isolation by high pressure liquid chromatography and characterization by 13C nuclear magnetic resonance spectroscopy
Published Jan 1, 1984 · W. Taylor, T. T. Nakashima
Canadian Journal of Chemistry
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Abstract
Preparative-scale high pressure liquid chromatography on 3-acetyl-2-(2′,6′-dimethyl-5′-heptenyl)oxazolidine (1), a complex acetamide derivative of citronellal, resulted in isolation of the diastereomeric forms of this insect repellent. The two diastereomers were designated as 1a and 1b on the basis of their order of elution from silica gel and from a variety of capillary gas chromatography columns. Interpretation of the 13C nuclear magnetic resonance spectra of 1a and 1b was accomplished by comparison with model compounds and by off-resonance proton-decoupling experiments. Absolute stereochemical assignments were not made. Because of the amide group, the diastereomers existed in solution at ambient temperature as cis and trans rotational isomers, which caused nonequivalence of most of the carbon atoms, including the olefinic carbons at C-5′ and C-6′. trans Isomer (5) was concluded to be the major contributor to the rotational equilibrium. The spectrum of 3-acetyl-2-(4′-methyl-3′-pentenyl)oxazolidine (7) w...
The diastereomers of 3-acetyl-2-(2′,6′-dimethyl-5′-heptenyl)oxazolidine (1a) and (1b) show potential as insect repellents, with trans isomer (5) being the major contributor to rotational equilibrium.
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