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The photochemistry of 8-bromo-2'-deoxyadenosine. A direct entry to cyclopurine lesions.
Article
Authorship:
JIMENEZ, LILIANA BEATRIZ ; Susana Encinas ; Miguel A. Miranda ; Maria Luisa Navacchia ; Chryssostomos ChatgilialogluDate:
2004Publishing House and Editing Place:
ROYAL SOC CHEMISTRYMagazine:
Photochemical and Photobiological Sciences, vol. 3 (pp. 1042-1046) ROYAL SOC CHEMISTRYSummary *
The UV photolysis of 8-bromo-2´-deoxyadenosine has been investigated in different solvents and in the presence of additives like halide anions. Photolytic cleavage of the C-Br bond leads to formation of the C8 radical. In methanol, subsequent hydrogen abstraction from the solvent is the main radical reaction; however, in water or acetonitrile intramol. hydrogen abstraction from the sugar moiety, to give the C5´ radical, is the major path. This C5´ radical undergoes a cyclization reaction on the adenine and gives the aminyl radical. A rate const. of 1.8 105 s-1 has been measured by laser flash photolysis in CH3CN for this unimol. process. Product studies from steady-state photolysis in acetonitrile have shown the conversion of 8-bromo-2´-deoxyadenosine to 5´,8-cyclo-2´-deoxyadenosine in 65% yield and in a diastereoisomeric ratio (5´R) : (5´S) = 1.7. Evidence supporting that the equil. Br + Br- .dblharw. Br2- plays an important role in this synthetically useful radical cascade is obtained by regulating the relative concns. of the two reactive oxidizing species. Information provided by the agent in SIGEVAKey Words
radicalsdeoxyadenosineoxidative damagephotochemistry