ABSTRACT Glycosylation requires a glycosyl donor with a leaving group and a glycosyl acceptor with an unprotected hydroxyl group because of the formation of regioselective and stereoselective glycosidic bonds. In this study, we explored the process of β-1,3-glycosylation using glycosyl donors and acceptors protected by acyl groups through a facile protocol to synthesize a β-1,3-glucan disaccharide, a constituent segment of β-1,3-glucan, which is an important molecule that induces immunological responses. However, conventional glycan synthesis requires a multistep reaction procedure to prepare a sugar donor and a sugar acceptor, and inevitably requires a large amount of starting materials. Therefore, we selected a simple synthesis method that does not require a multistep reaction and expensive reagents. We synthesized glycosyl donors and acceptors using 1,2:5,6-di-O-isopropylidene-α-d-glucofuranose, a commercially available glucose derivative, as the starting material with an unprotected hydroxy group only at the 3-position. Moreover, the acetyl and benzoyl groups were used as protecting groups. The glycosylation using acyl protected glycosyl donors and acceptors selectively gave the desired β-1,3-disaccharides. However, while benzoyl groups were expected to interfere with orthoester formation by steric hindrance during glycosylation, glycosylation using glycosyl donor and acceptor protected by the benzoyl groups resulted in the formation of the orthoester. The β-1,3-glucan synthesis proceeded more efficiently with the benzoyl glycosyl donor and acetyl glycosyl acceptor. Although this facile synthesis warrants additional scrutiny regarding protecting groups, the preparation of β-1,3-glucan oligosaccharides was accomplished expeditiously, underscoring the practicality of this method.
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