Regioselective Monoacetylation of Methyl Pyranosides of Pentoses and 6‐Deoxyhexoses by Acetic Anhydride in the Presence of MoCl5

Abstract Convenient regioselective syntheses of 3‐acetates of methyl pyranosides of α‐L‐rhamnose, α‐ and β‐L‐arabinose, α‐D‐fucose, α‐D‐lyxose, and β‐D‐ribose with good yields have been attained using MoCl5 as catalyst. Methyl β‐L‐rhamnopyranoside under this conditions gave 2‐acetate.