Independent Photochemical Generation and Reactivity of Nitrogen-Centered Purine Nucleoside Radicals from Hydrazines

Abstract

Photochemical precursors that produce dA^• and dG(N₂-H)^• are needed to investigate their reactivity. The synthesis of two 1,1-diphenylhydrazines (1, 2) and their use as photochemical sources of dA^• and dG(N₂-H)^• is presented. Trapping studies indicate production of these radicals with good fidelity, and 1 was incorporated into an oligonucleotide via solid-phase synthesis. Cyclic voltammetric studies show that reduction potentials of 1 and 2 are lower than those of widely used "hole sinks", e.g., 8-oxodGuo and 7-deazadGuo, to investigate DNA-hole transfer processes. These molecules could be useful (a) as sources of dA^• and dG(N₂-H)^• at specific sites in oligonucleotides and (b) as "hole sinks" for the study of DNA-hole transfer processes.

Figure 1

Mass spectrometric identification of recombination product 10 formed from photolysis of (a) 1 (b) 8-²H^-1.

Figure 2

Reduction potentials of nucleoside radical cations versus NHE in CH₃CN.

Scheme 1

Neutral Purine Radical Formation.

Scheme 2

Diphenylhydrazine Synthesis.

Scheme 3

Product Formation From Photolysis of 1.