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Background: Disaccharide core 1 (Galβ1-3GalNAc) is a common O-glycan structure in nature. Biochemical studies have confirmed that the formation of the core 1 structure is an important initial step in O-glycan biosynthesis and it is of great importance for human body. Objective: Our study will provide meaningful and useful sights for O-glycan synthesis and their bioassay. And all the synthetic glycosides would be used as intermediate building blocks in the scheme developed for oligosaccharide construction. Methods: In this article, we firstly used chemical procedures to prepare core 1 and its derivative, and a novel disaccharide was efficiently synthesized. The structures of the synthesized compounds were elucidated and confirmed by 1H NMR, 13C NMR and MS. Then we employed three human gut symbionts belonging to Bacteroidetes, a predominantphyla in the distal gut, as models to study the bioactivity of core 1 and its derivative on human gut microbiota. Results: According to our results, both core 1 and derivative could support the growth of B. fragilis, especially the core 1 derivative, while failed to support the growth of B. thetaiotaomicron and B. ovatus. Conclusion: This suggested that the B. fragilis might have the specificity glycohydrolase to cut the glycosidic bond for acquiring monosaccharide.

The total synthesis of 2d‐deoxy Lewisxpentasaccharide is described. Ethyl 2‐O‐acetyl‐3,4,6‐tri‐O‐benzyl‐1‐thio‐α,β‐D‐galactopyranoside was condensed with a diol of glucosamine to regio‐ and stereoselectively give the disaccharide, the C‐2′ position was then reduced after stereoselective fucosylation to afford a Lewisxtrisaccharide analogue. Regioselective glycosylation of a known lactoside diol with this trisaccharide provided a pentasaccharide that, after deprotection, gave the target pentasaccharide.