New aspects of organophosphorus pesticides. II. Structure and bioactivity of Orthene® insecticide analogs

Abstract

O,S-Dimethyl phosphoramidothioate was jointly commercialized in the United States as Monitor® Insecticide¹ by Chevron Chemical Company and Chemagro, and as Tamaron in Europe by Farbenfabriken Bayer. This exceptional insecticide/acaricide was discovered in 1964 by Lorenz at Bayer (Shrader et al. 1972) and by Magee (1967 Patent-Monitor, 1972 Patent-Orthene) at Chevron Chemical. Both groups carried out extensive modifications within the class leading to subsequent patents. Based on simplicity, efficacy and economics, Monitor Insecticide survived as the most important member of its class and became a commercial reality in 1970. It has many virtues as a systemic broad-spectrum insecticide of good residual life and is expected to have a world-wide impact on many important crops. Hammann (1970) described the bioactivity of Monitor Insecticide in some detail. While safe to handle due to moderate dermal toxicity [LD₅₀ (rats) 110 mg/kg (Hammann 1970)], Monitor and all of its simple analogs have relatively high oral toxicity [LD₅₀ (rats) 20 mg/kg].