Independent generation and reactivity of 2 '-deoxy-5-methyleneuridin-5-yl,a significant reactive intermediate produced from thymidine as a result ofoxidative stress

2'-Deoxy-5-methyleneuridin-5-yl (1) is produced in a variety of DNA damage processes and is believed to result in the formation of lesions that are mu tagenic and refractory to enzymatic repair. 2'-Deoxy-5-methyleneuridin-5-yl (1) was independently generated under anaerobic conditions via Norrish Typ e I photocleavage during Pyrex filtered photolysis of the benzyl ketone 7. The radical (1) exhibits behavior consistent with that of a resonance-stabi lized radical. The KIE for hydrogen atom transfer from t-BuSH was found to be 7.3 +/- 1.7. Competition studies between radical recombination and hydro gen atom donors (2,5-dimethyltetrahydrofuran, k(Trap) = 46.1 +/- 15.4 M-1 s (-1); propan-2-ol, k(Trap) = 13.6 +/- 3.5 M-1 s(-1)) chosen to mimic the ca rbohydrate components of 2'-deoxyribonucleotides suggest that 2'-deoxy-5-me thyleneuridin-5-yl (1) may be able to transfer damage from the nucleobase t o the deoxyribose of an adjacent nucleotide in DNA under hypoxic conditions .