ESR1 and breast cancer: Some derivatives which possess two amino side chains (except morpholinyl) at positions 4′ of one or both of the extra benzene rings, and/or at position 7 of coumarin scaffold (compounds 55), proved to be more potent than tamoxifen against ER(+) MCF-7 and ER(−) epithelial human breast cancer (MDA-MB-231) cells, with IC50 < 10 μM, and showed a broad-spectrum and good anti-proliferative activities, with an intercalative mode of binding against five tumor cells and low cytotoxicity in osteoblast [135,136].