Correlations between structure of nitrostyrene derivative fungicides and their reactivity toward low molecular weight thiols

Abstract

Reactivity of 27 fungitoxic β-nitrostyrene derivatives against l-cysteine, glutathione, and 2-mercaptoacetic acid was studied for modeling their reactions with essential sulfhydryl groups in fungi. A significant linear correlation was found between the reactivity of ring-substituted derivatives and the Hammett σ constant of the substituents in the case of each thiol. Principal component analysis and stepwise regression analysis were used to reveal other possible correlations. The reactivity order of nitrostyrene derivatives against the three thiols was very similar. The reactivity was increased the most by nitro and cyano substitutions (except substitutions in the ortho position), the presence of halogen atoms influenced to a lesser extent the reactivity of each parent compound. Ortho substitutions generally lessened the reaction rate. Methyl substitution on the α carbon atom of the styryl double bond strongly decreased the reaction rate. The molecular lipophilicity of these nitrostyrene derivatives did not significantly influence the reaction rates.