Design, synthesis, and biological evaluation of cyclopropyl analogues of stilbene with raloxifene side chain as subtype-selective ligands for estrogen receptor

We have designed the cyclopropane analog of stilbene as subtype-selective ligands for estrogen receptor based on the bioisosterism that cyclopropane could act as alkene bioisoster. Three cyclopropane analogs were prepared efficiently starting from 4-benzyloxybenzaldehyde, and evaluated for their binding to estrogen receptors ER alpha and ER beta. These cyclopropane analogs were also found to be full agonists in estrogen receptor-mediated gene transcription assay. Compared to the stilbene analogs such as tamoxifen and raloxifene, the three cyclopropane analogs showed lower binding affinity for estrogen receptor, but higher subtype selectivity for ER alpha. The structure-activity relationship revealed from this study might provide clues for improving subtype selectivity for ER alpha.