Deoxyribonolactone formation in photoirradiation of 5-bromouracil-containing oligonucleotides by direct C1′ hydrogen abstraction

Mechanistic studies on the formation of deoxyribonolactone by UV irradiation of hexamer d(GC1BrUGC)2 (ODN 2a) containing 1′-deuterio-2′-deoxyadenosine 1 was examined. The kinetic isotope effect (kH/kD) for the formation of C1′ oxidation product 3 was 1.7±0.1. ESI-MS of d(pUGC) (7) obtained from the photoreaction of ODN 2a indicated that 1′ deuterium was abstracted by uracilyl-5-yl radical and incorporated into 7 in 96% yield.