Synthesis and UV photolysis of oligodeoxynucleotides that contain 5-(phenylthiomethyl)-2 '-deoxyuridine: A specific photolabile precursor of 5-(2 '-deoxyuridilyl)methyl radical

The title exocyclic radical (2) is generated via photochemical cleavage of 5-(phenylthiomethyl)-2'-deoxyuridine (8). The latter thionucleoside (8) was successfully incorporated into DNA oligomers by automated DNA synthesis us ing phosphoramidite chemistry. UV exposure of 8 containing oligonucleotides under (an)aerobic conditions gives rise to specific base lesions, The phot oproducts have been isolated and further characterized on the basis of deta iled NMR and mass spectrometric analyses.