Quantitative structure-activity relationships (QSAR) of two series of O-aryl or N-aryl O-ethyl phosphoramidate and phosphorodiamidate fungicides incorporating amino acid ethyl esters

Structure-activity relationships of wide groups of fungicides have been exa mined e.g. aliphatic aldehydes, ketones and alcohols (Andersen et al. 1994) , alicyclic diamines (Havis et al. 1996), substituted 2-phenylbenzofurans ( Chamberlain and Carter 1980), hydroxamic acids (Bravo and Late 1996), heter ocyclic nitrogen compounds (Chen et al. 1997) and some organophosphorus com pounds (Cremlyn et al. 1974; Roy et al. 1996; Dureja et al. 1980). These qu antitative structure activity relationships have been used to predict the t oxicity of new compounds, correlate bioactivity of chemicals with their phy sicochemical properties and shed light on the nature of fungicide-biorecept or interaction. Physicochemical descriptors used included the stereoelectro nic parameters and the substituent parameters, pi, characterizing hydrophob icity (Hansch and Leo 1979). It was also mentioned that attachment of an am ino acid to a drug enhances its cellular uptake (Chen et al. 1994). Therefo re, to extend the study of the biological effects and quantitative structur e-activity relationships of pesticides and chemicals (Ali and Mostafa 1999; Ismail et al. 1993; Ali et al. 1999), a QSAR study has been performed to c orrelate the fungicidal activities of two series, O-aryl O-ethyl phosphoram idates and N-aryl O-ethyl phosphorodiamidates containing an amino acid este r moiety, with their electronic, steric and hydrophobic parameters.