Reported herein is the synthesis of sialyl LewisX analogues bearing a trans-bicyclo­[4.4.0] dioxadecane-modified 3-O,4-C-fused galactopyranoside scaffold that locks the carboxylate pharmacophore in either the axial or equatorial position. This novel series of bicyclic galactopyranosides are prepared through a stereocontrolled intramolecular cyclization reaction that has been evaluated both experimentally and by density functional theory calculations. The cyclization precursors are obtained from β-d-galactose pentaacetate in a nine-step sequence featuring a highly diastereoselective equatorial alkynylation and Cu­(I) catalyzed formation of the acetylenic α-ketoester moiety. Preliminary biological evaluations indicate improved activity as P-selectin antagonists for the axially configured analogues as compared to their equatorial counterparts.

A new synthesis of the fungal lipo‐chitooligosaccharide Myc‐IV (C16:0, S), which was recently reported to be a major symbiotic signalling molecule in arbuscular mycorrhiza, is described. Key steps include the oxidative cleavage of a 4,6‐O‐benzylidene acetal to prepare a disaccharidic glycosyl acceptor, and stereoselective glycosylations with 2‐methyl‐5‐tert‐butylphenyl thioglycosyl donors.

An environmentally improved synthesis of the N‐differentiated chitotetrasaccharide CO‐IV‐(NH2), a key intermediate for the preparation of lipochitooligosaccharides and the TMG‐chitotriomycin, is reported based on a chromatography‐free ionic‐liquid tagging approach. The method involves the glycosylation of ionic‐liquid‐tagged acceptors with thioglucosamine donors leading to the stereoselective formation of β‐(1→4)‐linked glucosamine‐containing oligomers.