Modular Synthesis of Nona‐Decasaccharide Motif from Psidium guajava Polysaccharides: Orthogonal One‐Pot Glycosylation Strategy

Recent Advances in Chemical Synthesis of Structural Domains of Lipopolysaccharides from the Commensal Gut-Associated Microbiota

Lipopolysaccharides from the commensal gut-associated microbiota are interesting biomolecules for the treatment of various inflammatory diseases. Different from pathogenic lipopolysaccharides, commensal lipopolysaccharides have distinct chemical structures and mediate beneficial homeostasis with the immune system of the host. However, the accessibility issues of homogenous and pure commensal lipopolysaccharides hampered the in-depth studies of their functions. In this concept article, we highlight the recent synthesis of lipopolysaccharides from gut-associated lymphoid-tissue-resident Alcaligenes faecalis and Bacteroides vulgatus, which hopes to inspire the more efforts devoting to these fantastic biomolecules.

Convergent Synthesis and Anti-Pancreatic Cancer Cell Growth Activity of a Highly Branched Heptadecasaccharide from Carthamus tinctorius

Bioactive polysaccharides from natural resources target various biological processes and are increasingly used as potential target molecules for drug development. However, the accessibility of branched and long complex polysaccharide active domains with well-defined structures remains a major challenge. Herein we describe an efficient first total synthesis of a highly branched heptadecasaccharide moiety of the native bioactive galectin-3-targeting polysaccharide from Carthamus tinctorius L. as well as shorter fragments of the heptadecasaccharide. The key feature of the approach is that a photo-assisted convergent [6+4+7] one-pot coupling strategy enables rapid assembly of the heptadecasaccharide, whereby a photoremovable o-nitrobenzyl protecting group is used to generate the corresponding acceptor for glycosylation in situ upon ultraviolet radiation. Biological activity tests suggest that the heptadecasaccharide can target galectin-3 and inhibit pancreatic cancer cell growth.

Merging Reagent Modulation and Remote Anchimeric Assistance for Glycosylation: Highly Stereoselective Synthesis of α-Glycans up to a 30-mer

The efficient synthesis of long, branched, and complex carbohydrates containing multiple 1,2-cis glycosidic linkages is a long-standing challenge. Here, we report a merging reagent modulation and 6-O-levulinoyl remote anchimeric assistance glycosylation strategy, which is successfully applied to the first highly stereoselective synthesis of the branched Dendrobium Huoshanense glycans and the linear Longan glycans containing up to 30 contiguous 1,2-cis glucosidic bonds. DFT calculations shed light on the origin of the much higher stereoselectivities of 1,2-cis glucosylation with 6-O-levulinoyl group than 6-O-acetyl or 6-O-benzoyl groups. Orthogonal one-pot glycosylation strategy based on glycosyl ortho-alkynylbenzoates and ortho-(1-phenylvinyl)benzoates has been demonstrated in the efficient synthesis of complex glycans, precluding such issues as aglycon transfer inherent to orthogonal one-pot synthesis based on thioglycosides.