Synthesis of beta-D-mannosides from beta-D-glucosides via an intramolecular SN2 reaction at C-2.

The selective synthesis of beta-D-mannosides was achieved by first synthesizing beta-D-glucosides that carry a N-phenylcarbamoyl protecting group at O-3. These derivatives were transformed into the corresponding beta-D-mannosides by intramolecular nucleophilic substitution with inversion of configuration at C-2, the O-trifyl group being the leaving group. Subsequent intramolecular attack of the neighboring carbamoyl group resulted in the formation of the 2,3-carbonate of the desired beta-D-mannoside.