Stabilization of sialyl cation in axial conformation assisted by remote acyl groups

Abstract

Stereoselective synthesis of α-sialosides by the glycosylation reaction (sialylation) is an important task in carbohydrate chemistry. Using quantum chemical calculations, the conformations of the sialyl cation formed from the sialyl donor under conditions of sialylation reaction were studied. Although the "axial conformation" of sialyl cation itself is energetically unfavorable, it is possible to stabilize it through the participation of O- and N-acyl protective groups. The obtained results open the possibility to modulate the stereoselectivity of sialylation by directed variation of the nature of protective groups in the sialyl donor molecule. 2