Crystal Structure of the ER-alpha Ligand-binding Domain (Y537S) in Complex with the OBHS-BSC Analog, 3-fluorophenyl (1R,2R,4S)-5-(4-hydroxyphenyl)-6-(4-(2-(piperidin-1-yl)ethoxy)phenyl)-7-oxabicyclo[2.2.1]hept-5-ene-2-sulfonate and 3-methyl-6-phenyl-3H-imidazo[4,5-b]pyridin-2-amine