Development of insecticidal cyclic phosphoryl compounds through chemical and biochemical approaches

Chemical and biochemical studies on three types of cyclic phosphoryl compounds are discussed in connection with the development of insecticides. They are five-membered cyclic phosphoramidates (I), six-membered cyclic phosphates (II) and bridged bicyclic phosphates (III). Development of I has started from the finding of L-leucine as a neuroactive substance in silkworm blood, followed by its combination with chemically active five-membered cyclic phosphates. Studies on the metabolism of neurotoxic tri-o-tolyl phosphate caused the invention of the insecticide salithion in the series of II. Salithion was chemically converted into its thiolo isomers, which is a convenient phosphorylating agent useful to synthesize biologically interesting phosphate esters. III does not inhibit acetylcholin-esterase but acts as an anti-GABA agent.