Facile Photocyclization Chemistry of 5-Phenylthio-2‘-deoxyuridine in Duplex DNA

We report here the synthesis of 5-phenylthio-2‘-deoxyuridine (d^PhSU), its incorporation into oligodeoxynucleotides (ODNs), and its photocyclization chemistry. Irradiation of dinucleoside monophosphate d(^PhSUG) and d^PhSU-bearing duplex ODNs with 254 nm light results in the facile formation of a cyclic product where the C6 of uracil is covalently bonded to the C2 of the phenyl ring. The chemistry reported here may serve as the basis for the efficient preparation of a new class of duplex DNA with an extended π system.