The oxidative steps from ent-kaurene to ent-kaurenoic acid are known to be dependent on cytochrome P-450. A structural feature common to tetcyclacis and the triazole-type compounds is an sp2-hybridised nitrogen atom located at the periphery of the molecule in a heterocycle. It appears likely that the lone electron-pair on this atom interacts with the central iron atom of cytochrome P-450 in the enzymes, resulting in inhibition.