Structure-activity relationship study of the inhibition of adrenal cortical 11.beta.-hydroxylase by new metyrapone analogs

Metyrapone, 2-methyl-1,2-di-3-pyridyl-1-propanone (1a), is a potent reversible inhibitor of the cytochrome P-450 11 beta-hydroxylase enzyme system (P-450(11) beta) of the adrenal cortex. The structural features of the metyrapone molecule have been systemically altered to determine the requirements necessary for inhibition of P-450(11) beta activity. Metyrapone and 14 analogues have been obtained or synthesized and evaluated as inhibitors using a crude, defatted bovine adrenal cortical mitochondrial preparation. The inhibition of P-450(11) beta activity with these derivatives demonstrated that (1) the A-ring phenyl derivatives 2a-d were better inhibitors than the respective dipyridyl analogues, (2) the ketone in the 1-position can be replaced by various functionalities without markedly reducing inhibition, and (3) at least one methyl group should be present in the 2-position to maintain inhibition. The observed inhibition of P450(11) beta activity with the metyrapone analogues suggest that A-ring phenyl metyrapone analogues 2a-d would be candidates for radioiodination and subsequently used as adrenal cortical imaging agents.