Synthesis of 5-methylmercaptopyrimidine nucleosides

The synthesis of a series of new nucleosides, including ribo-, 2′-deoxyribo- and arabinofuranosides of 5-(S-methyl)mercapto-substituted uracil, 4-thiouracil, and cytosine is described. The synthetic methods employed include condensation reactions of the silylated pyrimidine with blocked sugar halides, as well as transformations of both the base and sugar moieties. The separated α and β anomers were identified by nmr spectra as well as by unambiguous synthetic routes or interconversions.