No abstract

A series of 2-anilinopyrimidines was prepared and their fungicidal activities against Botrytis cinerea Pers were examined. The activity fell sharply with any substitution on the anilinobenzene ring. Substituents at the 5-position of the pyrimidine ring greatly reduced the activity. Substituents such as chloro, methoxy, methylamino, methyl or 1-propynyl were well tolerated at the 4- and 6-positions of the pyrimidine ring. Among these substituents, the combination of methyl and 1-propynyl groups was the most favourable. 2-Anilino-4-methyl-6-(1-propynyl)pyrimidine (KIF-3535), which showed excellent activity and no significant phytotoxicity, was finally selected for development and has been given the common name mepanipyrim.

Mepanipyrim, N-(4-methyl-6-prop-l-ynylpyrimidin-2-yl)aniline, hardly inhibited the mycelial respiration and the syntheses of DNA, RNA, protein, lipids and cell walls in mycelia of Botrytis cineyea at 100 eg/ml. By the treatment of mepanipyrim at 10-100 g/ml, each uptake of 14C-labeled glucose, acetate, uridine, thymidine, alanine or glucosamine by the mycelia of B. cineyea was inhibited, but no apparent uptake inhibition of these precursors was observed below 1, csg/ml. The inhibition by mepanipyrim of the active transport process across the cellular membrane may bring about a chronic deficiency in most intracellular substrates essential for growth and development. However, the effect of mepanipyrim appeared not to be strong enough to disrupt the overall functions of cell membrane in B. cineyea; because it neither stimulated the leakage of protein, phosphate, glucose and electrolytes from the cells, nor influenced the bursting rate of protoplasts by osmotic shock.

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Mepanipyrim exhibited excellent disease control activity against Botrytis cinerea, but poor activity against Cochliobolus miyabeanus; however, the mycelial growth of C. miyabeanus was inhibited more strongly than that of B. cinerea. Therefore, disease control efficacy by mepanipyrim in vivo is not correlated with mycelial growth inhibition in vitro. While mepanipyrim prevented pectinase secretion in B. cinerea at 0.1-1 mg/ml, it did not interfere with secretion in C. miyabeanus, even at 100 mg/ml, indicating that its action is an important mechanism in disease control. Mepanipyrim affected the uptake of glucose and phenylalanine in the mycelia of both pathogens at higher doses. Thus, a secondary action of mepanipyrim may bring about mycelial growth inhibition in vitro.