Quantitative Structure−Antifungal Activity Relationships of Some Benzohydrazides against Botrytis cinerea

Fourteen benzohydrazides have been synthesized and evaluated for their in vitro antifungal activity against the phytopathogenic fungus Botrytis cinerea. The best antifungal activity was observed for the N‘,N‘-dibenzylbenzohydrazides 3b−d and for the N-aminoisoindoline-derived benzohydrazide 5. A quantitative structure−activity relationship (QSAR) study has been developed using a topological substructural molecular design (TOPS-MODE) approach to interpret the antifungal activity of these synthetic compounds. The model described 98.3% of the experimental variance, with a standard deviation of 4.02. The influence of an ortho substituent on the conformation of the benzohydrazides was investigated by X-ray crystallography and supported by QSAR study. Several aspects of the structure−activity relationships are discussed in terms of the contribution of different bonds to the antifungal activity, thereby making the relationships between structure and biological activity more transparent. Keywords: Benzohydrazides; crop protection agents; Botrytis cinerea; antifungal activity; QSAR; spectral moments