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.