l-Allryl-4-chloro-2-(2,6-dichloro-4-hydroxyphenyl)-6-hydroxyindo(l4e,as l kyl =i CHa, CsHs, CaH,) were synthesized
by thermolysis of the corresponding NJV’-dialkyl-1,2-diphenylethylenediamineasn d subsequent ether cleavage. They showed an affinity for the estrogen receptor (1% of 178-estradiol) and inhibited the growth of the 9,lO-dimethyl-
l,2-benz[u]anthracene (DMBA) induced mammary carcinoma of the Sprague-Dawley (SD) rat. The best result was obtained by the ethyl compound (4b), which reduced the original tumor area by 50% after 4 weeks administration of 6 X 18 (mg/kg)/week. Since 4s and 4b show uterotrophic activity and cytostatic effects against hormone-independent cells, a dual mode of action has to be considered for the tumor inhibition.