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

[formula: see text] 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 using phosphoramidite chemistry. UV exposure of 8 containing oligonucleotides under (an)aerobic conditions gives rise to specific base lesions. The photoproducts have been isolated and further characterized on the basis of detailed NMR and mass spectrometric analyses.