Quantitative studies on structure - Activity relationship of sulfonylurea and benzoylphenylurea type pesticides and their substituents' bioisosterism using synthons' activity contribution

With the Free-Wilson mathematical model method in its Fujita-Ban variant, the quantitative structure-activity relationships of some famous pesticides, their substituents' quantitative bioisosterism sequence, and their physicochemical meaning analysis are studied. In the case of sulfonylurea herbicides, the heterocycle connected with the amino group of the urea part was found to play an important role in inhibition of rape rooting, which showed positive activity contribution accounted for by the highest occupied orbital energy E(HOMO) and the lowest unoccupied orbital energy E(LUMO) compared with the negative contribution of the substituents on the sulfonylphenyl ring. In the case of benzoylphenylurea type insect-growth regulators, the substituent X₁, at the benzoyl moiety, was found to play an important role in the inhibition of insects' chitin synthesis, which gave strong positive activity contribution mainly accounted for by electronic σ and steric Es parameters, whereas the substituent X₂ gave a negative to weakly positive activity contribution mainly resulting from hydrophobic π.