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The TpG chelate of cis(diammineplatinum) forms two head-to-head rotamers in H2O solution

Authors
  • Elizondo-Riojas, M.-A.1
  • Gonnet, Florence1
  • Chottard, Jean-Claude1
  • Girault, Jean-Pierre1
  • Kozelka, Jiří1
  • 1 Laboratoire de Chimie et Biochimie Pharmacologiques et Toxicologiques, URA CNRS 400, 45, Rue des Saints-Pères, F-75270 Paris Cedex 06, France, Tel.: +331-42 86 21 75; Fax: +331-42 86 83 87; e-mail: [email protected], FR
Type
Published Article
Journal
JBIC Journal of Biological Inorganic Chemistry
Publisher
Springer-Verlag
Publication Date
Feb 01, 1998
Volume
3
Issue
1
Pages
30–43
Identifiers
DOI: 10.1007/s007750050205
Source
Springer Nature
Keywords
License
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Abstract

d(TpG)– reacts with cis-[Pt(NH3)2(H2O)2]2+ in two steps to yield the platinum chelate cis-[Pt(NH3)2{d(TpG)-N3(1),N7(2)}]. In the latter, hindered rotation of the bases leads to an equilibrium between two rotamers interconverting slowly on the NMR time scale. The structure of the two rotameric chelates was studied by means of 1H NMR and molecular modeling techniques. The major and minor rotamers could be assigned unambiguously to the two head-to-head conformational domains which are characterized by syn/anti and anti/anti sugar-base orientations, respectively. Molecular models derived for both rotamers show that the orientations of the bases are mutually quasi-enantiomeric. The interconversion between the two rotamers (k ≈ 1 s–1 at 293 K) is approximately 104 times faster than the analogous rotamer interconversion observed in cis-[Pt(NH3)2{r(CpG)-N3(1),N7(2)}]+ [Girault J-P, Chottard G, Lallemand J-Y, Huguenin F, Chottard J-C (1984) J Am Chem Soc 106 : 7227–7232], suggesting that the steric clash of the exocyclic amino group of the platinum-bound cytosine with the ligands in cis position is more severe than that of the two thymine oxo groups.

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