Katsuzo Kamoshita

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.

殺菌活性を有するN-(3,4-diethoxyphenyl)-carbamate 類の定量的構造活性相関

For 30 N-(3,4-diethoxyphenyl)carbamoyl esters with various alcoholic moiety substituents, their fungicidal activity against Botrytis cinema resistant to benzimidazole fungicides was determined by the agar medium dilution method and the structure-activity relationships were analyzed by using the multiple regression technique. The hydrophobicity of the substituents was favorable to the activity. The activity was related parabolically to the maximum width of the substituents and the fl-branching of the substituents was detrimental to the activity. The preventive activity of compounds against gray mold of cucumber caused by the resistant B. cinerea was determined by the foliar application in pot tests. The

Development of a New Fungicide, Diethofencarb

Diethofencarb [isopropyl N-(3, 4-diethoxyphenyl)carbamate] is a new carbamate fungicide developed by Sumitomo Chemical Co., Ltd. This compound has an outstanding activity against benzimidazole-resistant gray mold of fruit trees, grapes, and vegetables caused by Botrytis cinerea. One of the most effective ways to cope with resistance of plant pathogens is considered to be the use of fungicides to which resistant strains show negatively correlated cross-resistance. Through extensive investigations to search for N-phenylcarbamates with a potent fungicidal activity against benzimidazole-resistant fungi, we synthesized an isopropyl N-phenylcarbamate having 3, 4-diethoxy substituents on the benzene ring, named diethofencarb, to which the resistant strains of B. cinerea exhibited negatively correlated cross-resistance. Diethofencarb controled benzimidazole-resistant strains of B. cinerea curatively as well as preventively and showed systemic activity in plants. This fungicide did not inhibit germination of conidia of the benzimidazole-resistant B. cinerea, but the germ tubes were distored and swollen. Their abnormal morphology was quite similar to that of the wild type isolates treated with a benzimidazole fungicide, carbendazim. In field trials, the combination of diethofencarb with carbendazim (Sumico®), another benzimidazole fungicide, thiophanatemethyl (Gtter®), or a dicarboximide fungicide, procymidone (Sumiblend®) showed excellent performance for control of gray mold diseases where benzimidazole-resistant strains and the wild type ones coexisted.