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Induced fit recognition of DNA by organometallic complexes with dynamic stereogenic centres

Parkinson, J.A. and Chen, H.M. and Novakova, O. and Bella, J. and Wang, F. and Dawson, A. and Gould, R.O. and Parsons, S. and Brabec, V. and Sadler, P.J. (2003) Induced fit recognition of DNA by organometallic complexes with dynamic stereogenic centres. Proceedings of the National Academy of Sciences, 100 (25). pp. 14623-14628. ISSN 1091-6490

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Abstract

Organometallic chemistry offers novel concepts in structural diversity and molecular recognition that can be used in drug design. Here, we consider DNA recognition by η6-arene Ru(II) anticancer complexes by an induced-fit mechanism. The stereochemistry of the dinuclear complex [((η6-biphenyl)RuCl(en))2-(CH2)6]2 + (3, en = ethylenediamine) was elucidated by studies of the half unit [(η6-biphenyl)RuCl(Et-en)]+ (2, where Et-en is Et(H)NCH2CH2NH2). The structures of the separated and diastereomers of 2 were determined by x-ray crystallography; their slow interconversion in water (t½ ≈ 2 h, 298 K, pH 6.2) was observed by NMR spectroscopy. For 2 and 3 the configurations are more stable than (73:27). X-ray and NMR studies showed that reactions of 2 and 3 with 9-ethylguanine gave rise selectively to diastereomers. Dynamic chiral recognition of guanine can lead to high diastereoselectivity of DNA binding. The dinuclear complex 3 induced a large unwinding (31°) of plasmid DNA, twice that of mononuclear 2 (14°), and effectively inhibited DNA-directed RNA synthesis in vitro. This dinuclear complex gave rise to interstrand cross-links on a 213-bp plasmid fragment with efficiency similar to bifunctional cisplatin, and to 1,3-GG interstrand and 1,2-GG and 1,3-GTG intrastrand cross-links on site-specifically ruthenated 20-mers. Complex 3 blocked intercalation of ethidium considerably more than mononuclear 2. The concept of induced-fit recognition of DNA by organometallic complexes containing dynamic stereogenic centers via dynamic epimerization, intercalation, and cross-linking may be useful in the design of anticancer drugs.