We have prepared several organometallic systems whose structures are closely analogous to that of tamoxifen, the drug used in the treatment of hormone-dependent breast cancers, but which now possess two basic aminoalkyl chains: O(CH₂)₃NMe₂. Despite the absence of a phenolic functionality, these ferrocenyl compounds 3, 4 and their organic analogue 5 recognize the estrogen receptor but in addition exhibit strong antiproliferative effects on hormone-dependent breast cancer cells (MCF-7), and also on hormone-independent ones (MDA-MB-231) with, in this case, an IC₅₀ value of about 0.4 μM. The ferrocenyl moiety does not create a major effect here compared to a purely organic aromatic group. On the other hand, the presence within the molecule of two vicinal basic entities, potentially allowing complexation to metal ions such as Zn²⁺, could perhaps be the key to the antiproliferative effectiveness of this series which operates via a different mechanism to that of hydroxytamoxifen 1 and hydroxyferrocifen 2. The behaviour of these new species is discussed. They possess the distinctive feature of combining a strong antiproliferative effect with intense antibacterial and antifungal activity.

A series of new 1-[di-(4-R-phenyl)-methylidenyl)]-[3]ferrocenophanes, where R = OH, NH₂, NHAc, and the phenyl substitution is mixed or identical, are highly antiproliferative against MDA-MB-231 and PC-3 cancer cells, with IC₅₀ values ranging from 0.05–5.6 μM on MDA-MB-231 and 0.02–12.5 μM on PC-3.

In the course of the preparation of a series of ferrocenyl derivatives of diethylstilbestrol (DES), in which one of the 4-hydroxyphenyl moieties was replaced by a ferrocenyl group, the McMurry reaction of chloropropionylferrocene with a number of mono-aryl ketones unexpectedly yielded the hydroxylated ferrocenyl DES derivatives, 5a–c, in poor yields (10%–16%). These compounds showed high activity on the hormone-independent breast cancer cell line MDA-MB-231 with IC₅₀ values ranging from 0.14 to 0.36 µM. Surprisingly, non-hydroxylated ferrocenyl DES, 4, showed only an IC₅₀ value of 1.14 µM, illustrating the importance of the hydroxyethyl function in this promising new series. For comparison, McMurry reactions of the shorter chain analogue chloroacetylferrocene were carried out to see the difference in behaviour with mono-aryl ketones versus a diaryl ketone. The effect of changing the length of the alkyl chain adjacent to the phenolic substituent of the hydroxylated ferrocenyl DES was studied, a mechanistic rationale to account for the unexpected products is proposed, and the antiproliferative activities of all of these compounds on MDA-MB-231 cells lines were measured and compared. X-ray crystal structures of cross-coupled products and of pinacol-pinacolone rearrangements are reported.