synthesis of hexofuranosyl 1-phosphates starting from new unprotected glycofuranosyl donors. It required first the preparation of new 1-thiohexofuranosides bearing a thioimidoyl heterocycle as a leaving group. The presence of sulfur and/or nitrogen atom(s) on the aglycon allowed remote activation of these thioglycofuranosides by anhydrous phosphoric acid and led to the target phosphates 9, 27, 29, and 30
Direct activation of unprotected thioimidoyl furanosides yielded in only one step and few minutes a panel of rare uridine 5'-diphosphofuranoses. Diastereoselectivity of the reaction was tightly connected with reaction time, temperature, and nature of the furanosyl donor. This approach was totally selective since no ring expansion from the initial five-membered ring to the more stable pyranose form was observed.