The Chiral Potential of Phenanthriplatin and Its Influence on Guanine Binding
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Lippard_The chiral.pdf
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Author(s)
Lippard, Stephen J.
Johnstone, Timothy
Date Issued
January 2014
Journal
Journal of the American Chemical Society
Publisher
American Chemical Society (ACS)
Citation
Johnstone, Timothy C., and Stephen J. Lippard. “The Chiral Potential of Phenanthriplatin and Its Influence on Guanine Binding.” Journal of the American Chemical Society 136, no. 5 (February 5, 2014): 2126–2134. © 2014 American Chemical Society
Version
Final published version
Abstract
The monofunctional platinum complex cis-[Pt(NH[subscript 3])[subscript 2]Cl(Am)][superscript +], also known as phenanthriplatin, where Am is the N-heterocyclic base phenanthridine, has promising anticancer activity. Unlike bifunctional compounds such as cisplatin, phenanthriplatin can form only one covalent bond to DNA. Another distinguishing feature is that phenanthriplatin is chiral. Rotation about the Pt–N bond of the phenanthridine ligand racemizes the complex, and the question arises as to whether this process is sufficiently slow under physiological conditions to impact its DNA-binding properties. Here we present the results of NMR spectroscopic, X-ray crystallographic, molecular dynamics, and density functional theoretical investigations of diastereomeric phenanthriplatin analogs in order to probe the internal dynamics of phenanthriplatin. These results reveal that phenanthriplatin rapidly racemizes under physiological conditions. The information also facilitated the interpretation of the NMR spectra of small molecule models of phenanthriplatin-platinated DNA. These studies indicate, inter alia, that one diastereomeric form of the complexes cis-[Pt(NH[subscript 3])[subscript 2](Am)(R-Gua)][superscript 2+], where R-Gua is 9-methyl- or 9-ethylguanine, is preferred over the other, the origin of which stems from an intramolecular interaction between the carbonyl oxygen of the platinated guanine base and a cis-coordinated ammine. The relevance of this finding to the DNA-damaging properties of phenanthriplatin and its biological activity is discussed.
MIT Department
Massachusetts Institute of Technology. Department of Chemistry
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DOI of Published Version
https://doi.org/10.1021/ja4125115
