The unprotected methyl l-arabinofuranosides, d-ribofuranosides and d-xylofuranosides are transformed into the corresponding S-acetyl-5-thio derivatives by the thio-Mitsunobu reaction. Mesylation and subsequent reaction with sodium hydrogen carbonate led, depending on the configuration of the intermediate, to 2, 5-anhydro-2-thio-or 3, 5-anhydro-3- thiopentofuranosides. Due to inversion at C-3 or C-2 during the intramolecular ...
