A theoretical study on the conformations of azadirachtin

The conformation and the charge distribution of azadirachtin were analysed using molecular mechanics and AM1 calculations. The present paper reports our computational efforts that aim to characterise the skeletal conformational behaviour of azadirachtin and to determine the conformational flexibility of the functional groups present in the molecule. Intramolecular interactions related to the electronic structure of the molecule are also discussed. In addition, a comparative analysis of the conformational characteristics of azadirachtin and its related methyl ether derivatives was included in our study. A critical examination of the functional groups present in azadirachtin and their methyl ether derivatives provide us with crucial information about the optimal relative conformation required to stimulate an antifeedant response. On the basis of our results, it is reasonable to conclude that the highly preferred conformation obtained for azadirachtin could play a significant role in the stimulation of biological activity.