Substituted derivatives of A-nor-5 alpha-androstane and A-nor-5 alpha-estrane--structure and affinity for hormonal receptors.

The interactions of A-nor-5 alpha-androstane and A-nor-5 alpha-estrane derivatives with the estrogen and androgen receptors, have been evaluated by measuring their relative binding affinities (RBAs), under two sets of incubation conditions in order to discriminate between potent agonists from weak agonists with potential antagonist activities. Surprisingly some of these compounds which do not possess a phenolic hydroxyl group interact somewhat markedly with the estrogen receptor. This interaction is characteristic of weak estrogens, with potential anti-estrogenic activity (RBA values decreasing when increasing time and temperature of incubation). Results are in good agreement with data obtained in vivo. Moreover, some of these compounds interact also to some extent with the androgen receptor. Results will be discussed in order to outline some structure-activity relationships in these series.