The Königs–Knorr condensation of 4,6-di-O-acetyl-2,3-O-carbonyl-α-D-mannopyranosyl bromide with 1,2,3,4-tetra-O-acetyl-β-D-glucose provides a synthetic route to 6-O-β-D-mannopyranosyl-D-glucose. When some other derivatives of α-D-mannopyranosyl bromide—the 2,3,4,6-tetra-O-benzoyl-, 3,4,6-tri-O-acetyl-, or 3,4,6-tri-O-acetyl-2-O-benzyl derivative—are used as the halide component the α-D-linked isomer of this disaccharide is produced. The steric outcome of Königs–Knorr syntheses involving these and other derivatives of α-D-mannopyranosyl bromide is discussed in terms of the influence of neighboring groups, and of conformational and solvent effects.Lead tetraacetate oxidation of 6-O-β-D-mannopyranosyl-D-glucose, followed by reduction, affords 4-O-β-D-mannopyranosyl-D-erythritol, a metabolite produced byUstilagospecies (PRL 627).