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Issue 32, 2007
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Antitumour bis(cyclopentadienyl) metal complexes: titanocene and molybdocene dichloride and derivatives

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Abstract

This Perspective will focus on recent developments in the field of antitumour metallocenes structurally related to titanocene dichloride. Despite extensive testing of titanocene dichloride which culminated in phase I and II clinical trials, further trials have been abandoned. While DNA has been implicated as the major target related to anticancer activity, identification of the active species and mechanism of action has been poorly understood and hence the design of second generation titanocene derivatives has not been possible. Recent mechanistic studies have provided a plausible mechanism for delivery of Ti to cancer cells via transferrin mediated endocytosis. This mechanism requires the presence of labile Cp–Ti bonds that hydrolyse on a time scale to deliver Ti to transferrin. A large range of titanocene derivatives in which the cyclopentadienyl rings have been substituted by both electron withdrawing and donating groups, including aromatic, alkyl and cyclic amines, have been prepared and tested for activity in the last 5 years. These results have shown that subtle structural effects can have a significant effect on biological activity and that biological activity is highly cell line dependent. However, the biological chemistry and cellular studies required to determine the mechanism of action of these new titanocenes have not been reported. In contrast, the bioorganometallic chemistry and cellular studies of molybdocene dichloride have implicated interaction with cellular thiols as the key reaction related to biological activity. Tailoring of the pseudohalide ligands by tuning the strength of the Mo–S bonds provides the opportunity to enhance cell uptake. Further research is required to establish the origin of antitumour activity.

Graphical abstract: Antitumour bis(cyclopentadienyl) metal complexes: titanocene and molybdocene dichloride and derivatives

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Article information


Submitted
16 May 2007
Accepted
05 Jul 2007
First published
20 Jul 2007

Dalton Trans., 2007, 3474-3482
Article type
Perspective

Antitumour bis(cyclopentadienyl) metal complexes: titanocene and molybdocene dichloride and derivatives

P. M. Abeysinghe and M. M. Harding, Dalton Trans., 2007, 3474
DOI: 10.1039/B707440A

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