Abstract: The detailed examination of intramolecular Diels-Alder reactions of several structurally related trienes led to construction of the desired tricyclic decalin moiety of azadirachtin with the a-hydroxyl groups at C1 and C3 as well as the oxygenated substituent at C8 in the naturally occurring form in good yields. Key words: azadirachtin, insect antifeedant, decalin, cyclic carbonate, intramolecular Diels-Alder reaction