Total synthesis of sialylated and sulfated oligosaccharide chains from respiratory mucins

The total syntheses of several complex oligosaccharide moieties that occur in the core structure of sulfated mucins are reported. A trisaccharide acceptor was obtained through regio-and stereoselective sialylation of methyl (6-O-pivaloyl-β-D-galactopyanosyl)-(1 → 3)-4,6-O-benzylidene-2-acetamido-2-deoxy-α-D-galactopyranoside with a novel sialyl donor. A tetrasaccharide, pentasaccharide, and hexasaccharide were constructed in predictable and controlled manner with high regio-and stereoselectivity after the successful preparation and employment of a disaccharide donor, trisaccharide donor, disaccharide acceptor, and trisaccharide acceptor building blocks. Finally, a mild oxidative cleaving method was adopted for the selective removal of 2-naphthylmethyl (NAP) in the presence of benzyl groups.