The photochemistry of 8-bromo-2'-deoxyadenosine. A direct entry to cyclopurine lesions - PubMed (original) (raw)

. 2004 Nov-Dec;3(11-12):1042-6.

doi: 10.1039/b410939b. Epub 2004 Oct 22.

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The photochemistry of 8-bromo-2'-deoxyadenosine. A direct entry to cyclopurine lesions

Liliana B Jimenez et al. Photochem Photobiol Sci. 2004 Nov-Dec.

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 x 10(5) s(-1) has been measured by laser flash photolysis in CH(3)CN 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(-)[right left harpoons] Br(2)*(-) plays an important role in this synthetically useful radical cascade is obtained by regulating the relative concentrations of the two reactive oxidizing species.

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