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Issue 11-12, 2004
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The photochemistry of 8-bromo-2′-deoxyadenosine. A direct entry to cyclopurine lesions

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Abstract

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 intramolecular 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 constant of 1.8 × 105 s−1 has been measured by laser flash photolysis in CH3CN for this unimolecular 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 equilibrium Br˙ + Br ⇌ Br2˙ plays an important role in this synthetically useful radical cascade is obtained by regulating the relative concentrations of the two reactive oxidizing species.

Graphical abstract: The photochemistry of 8-bromo-2′-deoxyadenosine. A direct entry to cyclopurine lesions

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Publication details

The article was received on 19 Jul 2004, accepted on 28 Sep 2004 and first published on 22 Oct 2004


Article type: Paper
DOI: 10.1039/B410939B
Citation: Photochem. Photobiol. Sci., 2004,3, 1042-1046
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    The photochemistry of 8-bromo-2′-deoxyadenosine. A direct entry to cyclopurine lesions

    L. B. Jimenez, S. Encinas, M. A. Miranda, M. L. Navacchia and C. Chatgilialoglu, Photochem. Photobiol. Sci., 2004, 3, 1042
    DOI: 10.1039/B410939B

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