Quantitative structure-activity relationship studies of the fungitoxic properties of phenethyl 1,2,4-triazoles

Abstract

A series of phenethyl triazoles was tested for activity in poisoned agar against Dreschlera sorokiniana, Piricularia oryzae, and a yeast sterol [ 14C]demethylase assay. The effects of substitution on the carbon adjacent to the phenyl ring and halogenation of the phenyl ring on activity was examined by regressing activity against substituent physicochemical parameters in a Hansch-type analysis. Results indicate that one substituent on the carbon adjacent to the phenyl ring should be 6–7 Å long. The terminal part of this substituent was negatively correlated to strong dipole moment, proton acceptor ability, or negative partial charge which implies a hydrophobic site. In general, the substitution patterns for the whole organism assays paralleled the activity of the demethylase assay. An exception was the para-phenyl position, whose optimum substituent varied by organism. The optimum substituent of the ortho-phenyl position varied with the substitution on the carbon adjacent to the phenyl ring. This interaction may be due to changes in the preferred conformation(s) of the molecule.