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'-hydroxyl 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 followed by regioselective hydroboration to obtain 7. Compound 7 was fully acetylated using acetic acid, acetic anhydride and sulfuric acid to obtain the key intermediate 8.