Two-Electron Oxidation of Deoxyguanosine by a Ru(III) Complex without Involving Oxygen Molecules through Disproportionation

• Published in: Inorganic chemistry Vol. 50; no. 14; pp. 6567 - 6574
• Main Authors: Choi, Sunhee, Ryu, DaWeon, DellaRocca, Joseph G, Wolf, Matthew W, Bogart, Justin A
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 18-07-2011
• Subjects: Deoxyguanosine - chemistry; Electrons; Hydrogen-Ion Concentration; Nucleic Acid Conformation; Organometallic Compounds - chemical synthesis; Organometallic Compounds - chemistry; Oxidation-Reduction; Ruthenium - chemistry
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/ic2003518

Among the many mechanisms for the oxidation of guanine derivatives (G) assisted by transition metals, RuIII and PtIV metal ions share basically the same principle. Both RuIII- and PtIV-bound G have highly positively polarized C8–H’s that are susceptible to deprotonation by OH–, and both undergo two-electron redox reactions. The main difference is that, unlike PtIV, RuIII is thought to require O2 to undergo such a reaction. In this study, however, we report that [RuIII(NH3)5(dGuo)] (dGuo = deoxyguanosine) yields cyclic-5′-O-C8-dGuo (a two-electron G oxidized product, cyclic-dGuo) without O2. In the presence of O2, 8-oxo-dGuo and cyclic-dGuo were observed. Both [RuII(NH3)5(dGuo)] and cyclic-dGuo were produced from [RuIII(NH3)5(dGuo)] accelerated by [OH–]. We propose that [RuIII(NH3)5(dGuo)] disproportionates to [RuII(NH3)5(dGuo)] and [RuIV(NH3)4(NH2 –)(dGuo)], followed by a 5′-OH attack on C8 in [RuIV(NH3)4(NH2 –)(dGuo)] to initiate an intramolecular two-electron transfer from dGuo to RuIV, generating cyclic-dGuo and RuII without involving O2.