α-Glucosaminide synthesis: exercising stereocontrol at C1 or C2 via torsional effects or DeShong nucleophiles

The synthesis of α-glucosaminides may be carried out by installing synthons for the cis-related C1 and C2 functionalities in either order. When the C2 azide is installed first, α-glycosidation can be induced by using a 4,6-O-benzylidene ring to provide torsional control of anomeric selectivity. In the alternative option, the C1 linkage can be established by use of an n-pentenyl-manno-1,2-orthoester, the C2oxygen of the resulting α-mannoside being replaced with inversion by use of DeShongʹs hypervalent silicon azide.