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Chemical synthesis of the trisaccharide repeating unit of the lipopolysaccharide fromMoritella viscosastrain M2-226 in the form of itsp-methoxyphenyl glycoside is reported. The synthesis was accomplished by using rationally protected monosaccharides prepared from commercially available D-glucose, D-glucosamine hydrochloride, and L-fucose. Stereoselective glycosylations were achieved through activation of thioglycosides using NIS and H2SO4-silica. [ABSTRACT FROM AUTHOR]

Herein, we devised a method for stereoselective O -glycosylation using an Ir(i)-catalyst which enables both hydroalkoxylation and nucleophilic substitution of glycals with varying substituents at the C3 position. In this transformation, 2-deoxy-α- O -glycosides were acquired when glycals equipped with a notoriously poor leaving group at C3 were used; in contrast 2,3-unsaturated-α- O -glycosides were produced from glycals that bear a good leaving group at C3. Mechanistic studies indicate that both reactions proceed via the directing mechanism, through which the acceptor coordinates to the Ir(i) metal in the α-face-coordinated Ir(i)-glycal π-complex and then attacks the glycal that contains the O -glycosidic bond in a syn -addition manner. This protocol exhibits good functional group tolerance and is exemplified with the preparation of a library of oligosaccharides in moderate to high yields and with excellent stereoselectivities., Competing Interests: The authors declare no competing financial interests., (This journal is © The Royal Society of Chemistry.)

A series of 3-deoxy-3- N -arylated-β-d-galactoside and -guloside derivatives have been synthesized by cesium fluoride/trimetylsilylaryl triflate-mediated benzyne generation and N -arylation of 3-deoxy-3-amino-β-d-galactosides and -gulosides, respectively. Evaluation as ligands to galectin-1, 2, 3, 4N ( N -terminal domain), 4C ( C -terminal domain), 7, 8N, 8C, 9C, and 9N revealed that the galactosides selectively bound galectin-9C, whereas the gulosides selectively bound galectin-9N. Hence, the N -aryl group induces galectin-9 selectivity and the ligand 3C-configuration acts as an epimeric selectivity switch between the two domains of galectin-9. Furthermore, MD simulations revealed that galacto derivatives in galectin-9C and gulo derivatives in galectin-9N find stable poses with specific interactions, which proposes a possible explanation to the gal/gulo 9 C /9N selectivity., Competing Interests: The authors declare the following competing financial interest(s): H.L. and U.J.N. are shareholders in Galecto Biotech AB, Lund, Sweden., (Copyright © 2019 American Chemical Society.)