Improved synthesis of unique estradiol-linked platinum(II) complexes showing potent cytocidal activity and affinity for the estrogen receptor alpha and beta

We have recently reported the synthesis of a platinum(II) complex, made of estradiol, the female sex hormone, and a cisplatin analog, an anticancer drug, linked together by an eleven carbon atoms chain. The novel estradiol-Pt(II) hybrid molecule was synthesized in nine chemical steps with 10% overall yield. This new compound has been tested in vitro on estrogen-dependent (MCF-7) and -independent (MDA-MD-231) (ER+ and ER−) cell lines. Interestingly, the biological activity was quite significant, more potent than that of cisplatin, the compound currently used in chemotherapy. The estrogen receptor binding affinity (ERBA) of this compound was very similar to that of 17β-estradiol (E2) on both estrogen receptors (ERs), α and β. In order to further study this type of molecule, we have decided to synthesize several analogs with the same estrogenic scaffold but with various chain lengths separating the estradiol from the toxic part of the molecule. This was planned in order to study the effect of the length of the linking chain on the biological activity of the hybrids. Four E2-Pt(II) hybrid molecules having 6–14 carbon atoms linking chain have been synthesized using a new synthetic methodology. They are synthesized in only eight chemical steps with 21% overall yield. The 17β-estradiol-linked platinum(II) complexes have been tested for their receptor binding affinity as well as for their cytocidal activity on several breast cancer cell lines. The synthesis and biological results are reported herein.