Synthesis of L-3 '-hydroxymethylribonucleosides

The target compounds were synthesized via the key intermediate carbohydrate 8, which was synthesized by first selectively protecting the 1'- and 2'-hy droxyl groups followed by selective tosylation of the 5'-hydroxyl group to obtain compound 3. The tosyl moiety was then replaced by a benzyl ether to obtain 4. Compound 4 underwent Dess-Martin oxidation to afford the ketone 5 . Compound 5 was subjected to Wittig olefination to afford the alkene 6 fol lowed by regioselective hydroboration to obtain 7. Compound 7 was fully ace tylated using acetic acid, acetic anhydride and sulfuric acid to obtain the key intermediate 8.