Ring-substituted 1,2-dialkylated 1,2-bis(hydroxyphenyl)ethanes. 3. Synthesis, estrogen receptor binding affinity, and evaluation of antiestrogenic and mammary tumor inhibiting activity of 2,2'-disubstituted butestrols and 6,6'-disubstituted metabutestrols.

The synthesis of symmetrically 2,2'-disubstituted butestrols [meso-2,3-bis(4-hydroxyphenyl)butanes] and of 6,6'-disubstituted metabutestrols [meso-2,3-bis(3-hydroxyphenyl)butanes] are described [2,2'-substituents: H (1), OH (2), F (3), Cl (4), Br (5), CH3 (6), and C2H5 (7); 6,6'-substituents: H (8), OH (9), Cl (10), and CH3 (11)]. Compounds 1-11 were obtained by reductive coupling of the corresponding 1-phenylethanols with TiCl3/LiAlH4 and separation of the meso diastereomers. The binding affinity of the test compounds to the calf uterine estrogen receptor was measured relative to that of [3H]estradiol by a competitive binding assay. With the exception of 9, all other compounds showed remarkably high relative binding affinity (RBA) values between 1.0 and 29% that of estradiol. Compounds 3 and 6 (RBA values: 15 and 29), as well as 10 and 11 (1.7 and 5.2), exceeded those of the corresponding unsubstituted compounds 1 and 8 (12 and 1.0). The compounds exhibited strong (3, 4, 6, and 7), moderate (1, 2, and 10), weak (11), or no (8) estrogenic activity in the uterine weight test of the immature mouse. Compounds 1, 2, 8, 10, and 11 showed antiestrogenic activity inhibiting the estrone-stimulated uterine growth (25-35% inhibition). Compound 11 led to a significant inhibition of the tumor growth when tested on the 9,10-dimethyl-1,2-benzanthracene induced, hormone-dependent mammary carcinoma of the Sprague-Dawley rat.