A novel synthesis of 4′-thionucleosides and a potential stereospecific route to pyrimidine nucleosides

Starting with the l-ascorbate derived epoxide 1, a di-t-butyl dithioacetal cyclisation route to 2′-deoxy-4′-thionucleosides has been developed. Based on an intermediate in this route, a novel and stereospecific route to α- or β-pyrimidine nucleosides has been conceived, but its implementation failed at a key ring-closure step.