Computerized molecular modeling studies on the interactions of the antiestrogen tamoxifen (1) and its analogues bound to the calcium-binding protein calmodulin have guided the rational design of more potent antagonists. Compounds with either three or four methylene units in the basic side chain or slim lipophilic 4-substituents were expected to be more potent. All compounds were tested for antagonism of the calmodulin-dependent activity of ...