Compounds of Formula (I) wherein R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, and R.sup.6 are as defined herein for Formula (IA) and Formula (IB), or a tautomer, prodrug, solvate, or salt thereof, pharmaceutical compositions containing such compounds, and methods of modulating estrogen receptor activity in a cell or patient or treating an estrogen receptor-mediated disorder, particularly breast and other cancers, in a patient in need thereof by administering an effective amount of compound of the invention thereto.