Miyazaki_1989_Pestic.Biochem.Physiol_33_11

Stereoselectivity on sulfoxidation of propaphos (1, O,O-dipropyl O-4-methylthiophenyl phosphate, Kayaphos) into propaphos sulfoxide (2, O,O-dipropyl O-4-methylsulfinylphenyl phosphate) with German cockroach and biological activity of both enantiomers of 2 were examined. Metabolic 2 was analyzed by chiral HPLC on CHIRALCEL OA with hexane-propan-2-ol (9:1) to determine that the enantiomeric ratio of (R)s-(+) to (S)s-(-)-2 was 56:44. Both enantiomers of 2 were prepared by optical resolution with the same chiral HPLC. (-)-2 was about threefold more potent as an inhibitor of German cockroach and bovine erythrocyte acetylcholinesterases, whereas (+)-2 was twofold more insecticidal to German cockroach. There is little difference of toxicity to the house fly and the green rice leaf hopper between the enantiomers of 2..