One-pot iterative glycosylations toward a tetrasaccharide related to the O-specific polysaccharide from Escherichia coli O132

Stereoselective Synthesis of the Gal‐α‐(1→3)‐Gal‐β‐(1→3)‐GlcNAc Trisaccharide: a new Ligand for DCAR and Mincle C‐Type Lectin Receptors

“…In the chosen methodology the two galactose derivatives 2-3 [26,27] and the glucosamine derivative 4 [28] were used as building blocks (Scheme 1). The galactose 2 [27] and the glucosamine derivative 4 [28] were prepared using previously reported protocols whereas the orthogonally protected galactose 3 was prepared starting from the known thioglycoside 5. [29] In particular, 5 was reacted with the 2-chloroacetyl chloride to afford the monoprotected 6, that was then acetylated in Scheme 1.…”

“…Structure of the trisaccharide 1, the two-galactose derivatives 2-3 [26,27] and the glucosamine derivative 4. [28] Reaction conditions for the synthesis of 3: a) chloroacetyl chloride, triethylamine, dichloromethane, r.t., 1 h; b) acetic anhydride, pyridine, 4-dimethylaminopyridine, dichloromethane, r.t., 2 h, 59 % yield over two steps; c) pyridine, water, 45 °C, 2 h, quantitative yield. standard conditions to give the fully protected galactose 7 (59 % yield).…”