Synthesis of d‑Galactosamine and d‑Allosamine Derivatives via a Microwave-Assisted Preparation of 1,6-Anhydroglucosamine

We report a microwave-assisted intramolecular anomeric protection (iMAP) of glucosamine, which facilitates concise transformation of 1,6-anhydroglucosamine into 1,6-anhydrogalactosamine and 1,6-anhydroallosamine. The iMAP simultaneously obviates both the <i>O</i>1 and <i>O</i>6 protection, and the differentiation between <i>O</i>3 and <i>O</i>4 can be well-controlled by the <i>N</i>2 functionality because of the hydrogen bonding between <i>N</i>2 and <i>O</i>4. Epimerization of <i>O</i>4 afforded the galactosamine derivative and that of <i>O</i>3 yielded allosamine.