Tricyclic triarylethylene antiestrogens: dibenz[b,f]oxepins, dibenzo[b,f]thiepins, dibenzo[a,e]cyclooctenes, and dibenzo[b,f]thiocins

The bridging groups O, S, CH2CH2, and SCH2 were used to produce a series of 26 tricyclic triarylethylenes. Their in vitro binding to rat uterine estrogen receptor was measured in a competitive binding assay. Antifertility and uterotrophic tests in rats showed that antiestrogenic activity was present. The most interesting series had a basic side chain, and the most potent compounds were 3-[2-(dimethylamino)ethoxy] -10-ethyl-11-(4-hydroxyphenyl)dibenzo[b,f]thiepin (7b) and 3-[2-(dimethylamino)ethoxy]-11-ethyl-12-(4-hydroxyphenyl)-5,6-dihydrodibenzo[a,e]-cyclooctene (7c), which had good binding (approximately 50% relative to estradiol) and good antiestrogenic activity (ca. one-half of the potency of tamoxifen, III). In this series, the O-bridged compound was the least active, and this is interpreted in terms of the flatness of the dibenzoxepin ring system. Sedative activity was found in some of the compounds.