3′-Selective modification of a 4′,5′-didehydro-5′-deoxy-2′,3′-epoxyuridine using nucleophiles

1-(2,3-Anhydro-5-deoxy-4,5-didehydro-α-l-erythro-pent-4-enofuranosyl)uracil was obtained by the treatment of 5′-iodo-2′,3′-epoxyuridine with LiHMDS in excellent yield. The pyrimidine nucleoside possesses quite unique vinyl epoxide moiety within the molecules. The reactions of with a variety of nucleophiles gave 3′-substituted pyrimidine nucleosides without the formation of the corresponding 2′-substituted isomers. In the case of NaN3 or PhSH, the corresponding 5′-adduct was obtained as a minor product together with the expected 3′-adduct.