Tautomers of One-Electron Oxidized Guanosine

8-Bromoguanine derivatives, such as 1a and 1b, capture electrons (eaq ) with quantitative formation of the corresponding debrominated nucleosides[1,2] and, therefore, they are efficient detectors of excess electron-transfer processes.[3] Indeed, in two recent papers 8-bromo-2'-deoxyguanosine (1b) was incorporated in a varietyof single- and doublestranded oligonucleotides and G-quadruplexes, and the reaction with eaq indicated that excess electron transfer is effective.