Synthesis of 4'-selenoribonucleosides.

We report herein the synthesis and structural aspects of 4'selenouridine (11) and 4'-selenocytidine (13), novel nucleoside derivatives. 4'Selenouridine (11) was synthesized via the stereoselective seleno-Pummerer reaction between an appropriately protected selenoxide 9 and a persilylated uracil. 4'-Selenocytidine (13) was prepared from 4'selenouridine derivative 10. To the best of our knowledge, this is the first example concerning introduction of a heterocycle into the alpha- position of a seleno atom.