A THEORETICAL-STUDY ON THE CONFORMATIONS OF AZADIRACHTIN

The conformation and the charge distribution of azadirachtin were anal ysed using molecular mechanics and AM1 calculations. The present paper reports our computational efforts that aim to characterise the skelet al conformational behaviour of azadirachtin and to determine the confo rmational flexibility of the functional groups present in the molecule . Intramolecular interactions related to the electronic structure of t he molecule are also discussed. In addition, a comparative analysis of the conformational characteristics of azadirachtin and its related me thyl ether derivatives was included in our study. A critical examinati on of the functional groups present in azadirachtin and their methyl e ther 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 hig hly preferred conformation obtained for azadirachtin could play a sign ificant role in the stimulation of biological activity.