Abstract
Alkenyl side chains in the alcohol moiety of natural pyrethroids and (S)-bioallethrin are easily oxidized by mixed function oxidases (mfo) and chemical oxidants, but the products have not been defined in detail. Thus, the absolute configuration of the 7-hydroxy derivative of (S)-bioallethrin, a major metabolite by mouse and rat liver microsomes, was examined by a modified Mosher's method which compared the 1H NMR spectra of the esters with both enantiomers of α-methoxy-α-(trifiuoromethyl)phenylacetic acid, and the (7R)-configuration was assigned for it indicating that the mfo attacked a (pro-R)-hydrogen at the 7-position of the pyrethroid. Further, oxidized products of the alcohol moieties by SeO2 and m-chloro-peroxybenzoic acid (MCPBA) were analyzed by NMR and GC-MS after their purification by HPLC. Both the regioselectivity of these reagents and their relative reactivity on the four different alkenyl side chains were similar to those of mammalian and insect mfo. This result indicated that SeO2, and MCPBA oxidation could be used as a model reaction for metabolic studies of pyrethroids.
