Quantitative structure-activity relationships of the fungicidal methyl N-phenylcarbamates☆

Abstract For 69 methyl N -phenylcarbamates having various benzene ring substituents, the fungicidal activity was determined against Botrytis cinerea resistant to benzimidazole fungicides by the agar medium dilution method. The structure-activity relationships were analyzed quantitatively using such physicochemical substituent parameters as hydrophobic π, steric B 5 , and HB (hydrogen bonding) with the Hansch-Fujita method (C. Hansch and T. Fujita, J. Amer. Chem. Soc. 86 , 1616 1964). The hydrophobicity of substituents was favorable to the acitivity. The effect was position-specific, the importance being in the order of ortho ≅ meta > para . The activity was related parabolically to the maximum width of one of the m -substituents having the larger dimension. The hydrogen acceptability of p -substituents enhanced the activity. The preventive activity of compounds against gray mold of cucumber caused by the resistant B. cinerea , which was determined by the foliar application in pot tests, was dependent on the magnitude of the fungicidal activity and hydrophobicity of the compounds as analyzed by the adaptive least-squares method.