Strategies for stereocontrol at C1 or C2 in syntheses of α-glucosaminides

The C1 and C2 stereocenters of α‐glucosaminides can be prepared by establishing the stereocenters in either order. For the former, a C2‐azido glucosyl donor is prepared first, and the restraining effect of a 4,6‐O‐benzylidene ring is used to induce α‐coupling. For the latter, the C1 linkage is prepared first by use of an n‐pentenyl‐manno‐1,2‐orthoester donor which ensures (a) clean α‐coupling and (b) a convenient C2‐ester. The C2‐ester is replaced with a triflate leaving group, and nucleophilic displacement is effected by use of a hypervalent silicon azide.