Recent Progress in 1,2-cis glycosylation for Glucan Synthesis

Controlling the stereoselectivity of 1,2-cis glycosylation is one of the most challenging tasks in the chemical synthesis of glycans. There are various 1,2-cis glycosides in nature, such as alpha-glucoside and beta-mannoside in glycoproteins, glycolipids, proteoglycans, microbial polysaccharides, and bioactive natural products. In the structure of polysaccharides such as alpha-glucan, 1,2-cis alpha-glucosides were found to be the major linkage between the glucopyranosides. Various regioisomeric linkages, 1 -> 3, 1 -> 4, and 1 -> 6 for the backbone structure, and 1 -> 2/3/4/6 for branching in the polysaccharide as well as in the oligosaccharides were identified. To achieve highly stereoselective 1,2cis glycosylation, including ff-glucosylation, a number of strategies using inter- and intra-molecular methodologies have been explored. Recently, Zn salt-mediated cis glycosylation has been developed and applied to the synthesis of various 1,2-cis linkages, such as alpha-glucoside and beta-mannoside, via the 1,2-cis glycosylation pathway and beta-galactoside 1,4/6-cis induction. Furthermore, the synthesis of various structures of alpha-glucans has been achieved using the recent progressive stereoselective 1,2-cis glycosylation reactions. In this review, recent advances in stereoselective 1,2-cis glycosylation, particularly focused on alpha-glucosylation, and their applications in the construction of linear and branched alpha-glucans are summarized.

Automated summary

Controlling the stereoselectivity of 1,2-cis glycosylation is a challenging task in glycans synthesis. Various regioisomeric linkages have been identified, and strategies using inter- and intra-molecular methodologies have been explored. Recent advances in Zn salt-mediated cis glycosylation and its applications in alpha-glucans construction are summarized in this review.