Automated Assembly of Starch and Glycogen Polysaccharides

Polysaccharides are Nature's most abundant biomaterials essential for plant cell wall construction and energy storage. Seemingly minor structural differences result in entirely different functions: cellulose, a beta (1-4) linked glucose polymer, forms fibrils that can support large trees, while amylose, an alpha (1-4) linked glucose polymer forms soft hollow fibers used for energy storage. A detailed understanding of polysaccharide structures requires pure materials that cannot be isolated from natural sources. Automated Glycan Assembly provides quick access to trans-linked glycans analogues of cellulose, but the stereoselective installation of multiple cis-glycosidic linkages present in amylose has not been possible to date. Here, we identify thioglycoside building blocks with different protecting group patterns that, in concert with temperature and solvent control, achieve excellent stereoselectivity during the synthesis of linear and branched alpha-glucan polymers with up to 20 cis-glycosidic linkages. The molecules prepared with the new method will serve as probes to understand the biosynthesis and the structure of alpha-glucans.

Automated summary

Polysaccharides are essential biomaterials in nature for plant cell wall construction and energy storage. Even minor structural differences can lead to entirely different functions. Recent research has developed a method to synthesize linear and branched α-glucan polymers with excellent stereoselectivity, providing new insights into the biosynthesis and structure of α-glucans.