Time-Resolved Spectroscopic Observation of Diphenylnitrenium Ion Reactions with Guanosine

Arylnitrenium ions have gained attention for their high reactivity toward guanosine, which in some cases has been linked to carcinogenesis. Although many studies have examined covalent addition reactions between arylnitrenium ions and guanosine, there is still some uncertainty regarding the attack position of nitrenium ions on guanosine and its derivatives. In this paper, we employ nanosecond transient absorption and nanosecond time-resolved resonance Raman spectroscopy to investigate the reaction between the N,N-di(4-bromophenyl) nitrenium ion (2) and guanosine. Our time-resolved spectroscopic results and photochemical product analysis results show that the reaction of guanosine with 2 generates an N7 intermediate that subsequently undergoes rearrangement and deprotonation to produce a C8 adduct. Comparing these results to our previous study between the 2-fluorenylnitrenium ion and guanosine indicates that the structure and properties of arylnitrenium ions are able to influence the reaction pathways and intermediate structures.