Efficient Oxidation of 2‘-Deoxyguanosine by Mn-TMPyP/KHSO5 to Imidazolone dIz without Formation of 8-Oxo-dG

Oxidation of 2‘-deoxyguanosine dG with the chemical nuclease Mn-TMPyP/KHSO 5 leads within one minute to a nearly quantitative amount of 2-amino-5-[(2-deoxy- β - d - erythro -pentofuranosyl)amino]-4 H -imidazol-4-one (dIz or imidazolone for short) (90%) in a non-oxygen-dependent pathway and without formation of 8-oxo-dG. This new mechanism of dIz formation involves, as a crucial first step, the abstraction of two electrons from guanine by a high-valent porphyrin−Mn(V) O species, leading to the dG + cation instead of the classical dG • + radical cation. We describe also the oxidation of imidazolone into the corresponding imidazolone N -oxide in the presence of KHSO 5 .