structure-activity relationship of varying the 6-n-alkyl substituents (C-1--C-7) to the time-dependent inactivation activity. All of the inhibitors synthesized were powerful to good competitive inhibitors of aromatase, with apparent Ki's ranging from 4.7 to 54 nM. The 6beta-ethyl (4b) and 6beta-n-pentyl (4e) compounds were the most potent among them (Ki = 4.7 and 5.0 nM for 4b and 4e, respectively).