A number of 1-[2-(2-substituted hydroxy-5-substituted phenyl)allyl]imidazole derivatives and their related compounds were newly synthesized. The allylimidazoles showed a potent activity in vitro against Botrytis cineyea, a phytopathogenic fungus. The relationship between structure and activity was examined quantitatively using physicochemical and structural parameters and regression analysis. Hydrophobicity of the molecule was the most important factor for the activity. The activity increased

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... the hydrophobicity increased and bulkiness of a substituent at the 5-position on the benzene ring decreased. Unsubstitution at the 5position on the benzene ring did not favor the activity, however. Conversion of a double bond of the allyl moiety to a single bond deteriorated the activity. The present series of allylimidazoles was higher in activity than the previous series of the corresponding 1-[1-(2-substituted hydroxy-5-substituted phenyl)vinyl]imidazoles, which has been reported.