Minimum Structural Requirements for Herbicidal Evaluation of 5-(R1)-6-(R2)-N-(R3-Phenyl)-Pyrazine-2-Carboxamide Analogues as New Class Potent Herbicide

Abstract

To search the minimum structural requirements for herbicidal evaluation of 5-(R1)-6-(R2)-N-(R3-phenyl)-pyrazine-2-carboxamide analogues (1–19) as new class potent herbicide, 3D-QSARs models between the substituents (R1-R3) changes of the analogues and their herbicidal activity were derived and discussed quantitatively using comparative molecular field analysis (CoMFA) and comparative molecular similarity indice analysis (CoMSIA) method. The herbicidal activity of the optimized CoMFA model I was principally dependent on steric fields. Also, it was found that the optimized CoMFA model I with the sensitivity to the perturbation (dq 2′/dr2 yy′=0.959) and the prediction (q2=0.414) produced by a progressive scrambling analyses were not dependent on chance correlation. Also, it was predicted that the herbicidal activity increases when large steric substituents were introduced to one part of ortho- and meta- position on N-phenyl ring as R3-substituent and small steric substituents to the other part.