Complex endocrine activity has been reported in certain aminoalkoxytriarylethylenes. l. 2 ICI 46474 (Nolvadex), the trans isomer of 1-p (2-dimethylaminoethoxypheny1)-1, 2-diphenylbut- l-ene, is an example. In rats, this compound is a potent estrogen antagonist but also displays weak and atypical estrogenic activity. It is purely estrogenic in mice, as is the cis isomer (ICI 47699) in both species. 3 The configuration of these isomers as structures 1 and 2 was ...