Radical-mediated furanose ring reconstruction from 2′,3′-seco-uridine

Starting from 5′-O-trityl-2′,3′-seco-uridine, reconstruction of a furanose structure was carried out by the following sequence of reactions: (1) regioselective introduction of a phenylselenenyl group to the 2′-position of the 2′,3′-seco-uridine, (2) oxidation and subsequent Wittig reaction of the 3′-hydroxyl group and (3) intramolecular radical reaction (5-exo-trig ring closure) leading to 3′-C-carbon-substituted 2′,3′-dideoxyuridine. Also studied is the Pummerer reaction of the 2′-phenylseleno derivative of 2′,3′-seco-uridine. The resulting product, an α-(acyloxy)phenylselenide, also serves as a substrate for the radical cyclization to allow the introduction of a hydroxyl group at the 2′-position of the reconstructed furanose ring.