Deltamethrin: the cream of the crop.

Replacement of the pyrethronyl alcohol portion of the natural pyrethrins with the 5-benzyl-3-furylmethyl moiety gave bioresmethrin, a synthetic pyrethroid of high potency and safety but with limited photostability. Introduction of novel substituents at the 3-position of the cyclopropane ring then led to the discovery of insecticidally active compounds with greatly improved potency. Systematic changes of both the alcohol and acid components gave second-generation pyrethroids (permethrin, cypermethrin, and deltamethrin) with improved potency and photostability suitable for agricultural use. Metabolic studies showed that the photostabilized compounds remained biodegradable. Deltamethrin, discovered in 1974, was the cream of the crop and remains 36 years later as one of the most important synthetic pyrethroid insecticides.