Stereochemical Studies of Alkyl Methylcyclohexaneacetates with13C NMR Spectroscopy in Relation to Their Attractiveness to the German Cockroach

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Abstract
All positional isomers of methyl methylcyclohexaneacetates were prepared. Their diastereomeric pairs were separated from one another by preparative GLC. Either the cis or trans configuration was assigned to each of these GLC fractions on the basis of the chemical shift values of the ring methyl carbons in their 13C NMR spectra, which were found closely approximate to those of the corresponding dimethylcyclohexanes. The conformational compositions of the thermodynamically less stable diastereomers were determined using the chemical shift values of the axial and equatorial methyl carbons as parameters. The isomers of propyl methylcyclohexane-acetates for the biological test were separated similarly, and their configurations were determined by comparing the shift values of their ring methyl carbons with those of the methyl esters. The relative activity between the diastereomeric pairs was evaluated by a comparative trap test. The result was : cis-4-methyl isomer > trans-4-methyl isomer; trans-3-methyl isomer > cis-3-methyl isomer; and, trans-2-methyl isomer > cis-2-methyl isomer. The cis-4-methyl isomer exhibited activity comparable to that of the parent compound.

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