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 acce ptor was obtained through regio-and stereoselective sialylation of methyl ( 6-O-pivaloyl-beta-D-galactopyanosyl)-(1 --> 3)-4,6-O-benzylidene-2-acetamid o-2-deoxy-alpha-D-galactopyranoside with a novel sialyl donor. A tetrasacch aride, pentasaccharide, and hexasaccharide were constructed in predictable and controlled manner with high regio- and stereoselectivity after the succ essful preparation and employment of a disaccharide donor, trisaccharide do nor, disaccharide acceptor, and trisaccharide acceptor building blocks. Fin ally, a mild oxidative cleaving method was adopted for the selective remova l of 2-naphthylmethyl (NAP) in the presence of benzyl groups.