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