Stereoselective Construction of β‐Mannopyranosides by Anomeric O‐Alkylation: Synthesis of the Trisaccharide Core of N‐linked Glycans

Abstract

AbstractA new and efficient approach for direct and stereoselective synthesis of β‐mannopyranosides by anomeric O‐alkylation has been developed. This anomeric O‐alkylation of mannopyranose‐derived lactols is proposed to occur under synergistic control of a kinetic anomeric effect and metal chelation. The presence of a conformationally flexible C6 oxygen atom in the sugar‐derived lactol donors is required for this anomeric O‐alkylation to be efficient, probably because of its chelation with cesium ion. In contrast, the presence of a C2 oxygen atom plays a minor role. This glycosylation method has been successfully utilized for the synthesis of the trisaccharide core of complex N‐linked glycans.