STRUCTURE-ACTIVITY-RELATIONSHIPS OF PYRIDYLCARBAMATES ACTIVE AGAINST BOTH BENZIMIDAZOLE-SENSITIVE AND BENZIMIDAZOLE-RESISTANT ISOLATES OF BOTRYTIS-CINEREA

A series of pyridylcarbamates showed high potency against cucumber gra y mould (Botrytis cinerea Pers.). The most potent compound, propargyl- N-(6-ethyl-5-iodo-2-pyridyl)carbamate was effective against an isolate sensitive to benzimidazole and dicarboximide fungicides as well as ag ainst an isolate resistant to both types of compound. QSAR analyses an d molecular modelling studies were carried out to investigate the stru ctural requirements for highly active compounds and the structural fea ture of the binding site of each strain. Significantly different QSAR equations were obtained only for substituents at the 6-position of the pyridine ring. An ethyl-sized pocket or an ethyl terminal recognition was suggested in the case of the sensitive or resistant isolate respe ctively. These results could explain the phenomenon of negatively corr elated cross-resistance between benzimidazoles and N-phenylcarbamate f ungicides. Substituent effects at the 5- or 2-position were governed b y steric factors. Substituent effects at the 3-position were explained by steric hindrance or by conformational effects. The propargyl-subst ituted compound above was the most desirable one from the viewpoint of QSAR.