Fluoronucleosides, Isothiocyanato C-Nucleosides, and Thioureylene Di-C-nucleosides via Cyclic Sulfates

Cyclic sulfates of N- and C-nucleosides (d-ribo and d-erythro configurations, respectively) are used to prepare 3‘-fluoro and 3‘-azido d-xylo N-nucleosides and l-threo C-nucleosides. The reduction of the 3‘-azido C-nucleosides (furan, imidazoline-2-thione, and pyrrole derivatives) gives 3‘-amino C-nucleosides, which, by reaction with thiocarbonyldiimidazole, are transformed into 3‘-isothiocyanato C-nucleosides. Reaction of the 3‘-amino with the 3‘-isothiocyanato C-nucleosides gives thioureylene di-C-nucleosides, a type of nucleotide analogue with a nonionic bridge isosteric of the phosphate group.