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A series of (a-methoxybenzyl)isoxazole derivatives (I) were synthesized and their fungicidal activities were assessed. Studies of the structure-activity relationship revealed the strongest fungicidal activity when the isoxazole moiety was comprised of a 3-methyl-5-isoxazolyl group. When position-2 of the phenyl ring in the benzyl moiety was substituted with a 4-phenyl-2, 3-diaza-l,3-pentadienyl group, good fungicidal activity was achieved. When the benzene ring in the 4-phenyl-2, 3-diaza-1,3-pentadienyl moiety was substituted with a 4-bromo, 4-trifluoromethoxy or 3, 4-dichloro group, good fungicidal activity was obtained. Among the 29 compounds examined, 5-[2-{4-(4-bromophenyl)-2, 3-diaza-1, 3-pentadienyl}a-methoxybenzyl]-3-methylisoxazole (23) showed potent activities against cucumber powdery mildew and cucumber downy mildew.

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A series of (a-methoxyimino-2-phenoxymethylbenzyl)heterocycle derivatives were synthesized and their fungicidal activities were assessed. Studies of the structure-activity relationships revealed the strongest fungicidal activity when the heterocycle moiety was comprised of 1-methyl-2-imidazolyl and 1, 3, 4-oxadiazol-2-ylgroups. When the benzene ring on the phenoxymethyl moiety was substituted with 2-methyl, 2, 5-dimethyl or 4-chloro-2-methyl,good fungicidal activity was obtained. Between the two geometrical isomers at the oxime moiety, the E-isomers of imidazole and oxadiazole derivatives were more active than the Z-isomers. Among the compounds examined, (E)-2-[2-(4-chloro-2-methylphenoxymethyl)-a-methoxyiminobenzyl]-1-methylimidazole (27) showed a potent activity against cucumber powdery mildew and cucumbergray mold.

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