Selective Synthesis of Some Aminosugars via Catalytic Aminohydroxylation of Protected 2,3-Unsaturated d-Gluco- and d-Galacto-2-hexenopyranosides.

The aminohydroxylation of methyl 4,6-di-O-(tert-butyldimethylsilyl)-2,3-unsaturated α-d-glucopyranoside proceeds in the presence of chloramine-T, OsO4 (4 mol %), (DHQ)2PHAL (5 mol %), and triethylbenzylammonium chloride (TEBAC) in both a stereoselective and a regioselective manner to produce protected methyl α-d-mannosamide as the sole product. In contrast, the reaction of methyl 2,3-unsaturated β-d-galactopyranoside under the same conditions produced a mixture of regioisomers, although the stereochemistry was perfectly controlled. The regioisomeric ratio was dependent on the nature of the protecting group and the ligand used.