Radiosynthesis and Metabolism in Rats of the 1R Isomers of the Insecticide Permethrin

Abstract

Permethrin [3-phenoxybenzyl (±)-cis,trozzs-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylate] is more stable in air and light than previous pyrethroids, and therefore has a greater potential for controlling a wide range of insect pests. Metabolism of the [1R,trans]- and [1R,cis]-esters, the active isomers of permethrin, following oral administration to rats at about 1 mg/kg, was examined using compounds labeled with 14C in the acid or alcohol moieties. These were synthesized either from [1R,trans]- or [1R,cis]-acid labeled in the side chain [Cl214C=CH-] or from alcohol labeled at α-CH2 or in the phenoxy substituent. The [1R,trans]- and [lR,cis]-esters are readily metabolized by ester cleavage, by hydroxylation of the geminal dimethyl group in the acid, or the phenoxy group of the alcohol, and by conjugation of the resulting carboxylic acids and phenols. The metabolites are quickly excreted and do not persist significantly in tissues. © 1976, American Chemical Society. All rights reserved.