Steroidal bivalent ligands for the estrogen receptor (ER) were designed using crystal structures of ERα dimers as a template. The syntheses of several 17α-ethynylestradiol- based bivalent ligands with varying linker compositions and lengths are described. The binding affinities of these bivalent ligands for ERα and ERβ were determined. In the two series of bivalent ligands that we synthesized, there is a clear correlation between linker ...