Investigation of Neighboring Group Participation in 3,4-Diacetylated Glycosyl Donors in the Gas Phase.

A key challenge in oligosaccharide synthesis is the stereoselective installation of glycosidic bonds. Each glycosidic linkage has one of two possible stereo-chemical geometries, α/β or 1,2-cis/trans. An established approach to install 1,2-trans glycosidic bonds is neighboring group participation (NGP), mediated by a 2-O-acyl group.

Characterization of glycosyl dioxolenium ions and their role in glycosylation reactions.

Controlling the chemical glycosylation reaction remains the major challenge in the synthesis of oligosaccharides. Though 1,2-trans glycosidic linkages can be installed using neighboring group participation, the construction of 1,2-cis linkages is difficult and has no general solution. Long-range participation (LRP) by distal acyl groups may steer the stereoselectivity, but contradictory results have been reported on the role and strength of this stereoelectronic effect.