Interactions of narcotics and their antagonists with human serum esterase. VIII: structure-activity relationships of benzomorphans.

N-alkylbenzomorphans follow the pattern established in our earlier papers for the interaction of opiates with human serum esterase: they have affinity for both the substrate-binding site of the enzyme and an allosteric site at which agonistic drugs accelerate enzyme action. Affinity for the substrate-binding site is a function of the hydrophobicity of the drug, while affinity to the allosteric site is increased by alkyl groups at N and at C--5 and decreased by a 2'-methoxyl group or by either a methyl or a hydroxyl group in the 9 beta position. The absolute D configuration (corresponding to that of natural morphine) appears to be more sensitive to factors modifying affinity. All but three of the benzomorphans studied are agonists; all agonists have lower affinity for the allosteric site than antagonists.