title: An alternative high yielding and highly stereoselective method for preparing an alpha-Neu5NAc-(2,6)-D-GalN3 building block suitable for further glycosylation.
abstract: This paper deals with new approaches to alpha-Neu5NAc-(2,6)-D-GalN3 building blocks, suitable as glycosylation donors. The major improvement, by comparison with the results of the literature, lies in the glycosylation step of a new d-galactosamine acceptor (tert-butyldimethylsilyl 3-O-acetyl-2-azido-2-deoxy-beta-D-galactopyranoside) with O-methyl-S-[methyl(5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-D-glycero-alpha-D-galacto-non-2-ulopyranosyl)onate] dithiocarbonate as the N-acetylneuraminic acid donor. The reaction affords the expected disaccharide in high yield (85%) and a complete alpha-Neu5NAc stereoselectivity. A subsequent oxidation step, eliminating the glycal by-product allows an easier purification. Afterwards, the tert-butyldimethylsilyl disaccharide can be transformed into a donor, after cleavage of the anomeric group in smooth conditions.
authors.affiliation: Laboratoire de Chimie Organique II-Glycochimie, Unité Mixte de Recherche CNRS 5181, Université Lyon 1, Chimie Physique Electronique de Lyon, 43 Boulevard du 11 Novembre 1918, F-69622 Villeurbanne, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Laurent
authors.forename: Dominique
authors.initials: D
authors.lastname: Lafont
authors.forename: Paul
authors.initials: P
authors.lastname: Boullanger
authors.forename: Jean Maurice
authors.initials: JM
authors.lastname: Mallet
mesh_terms: D001386:Azides / Q000138:chemical synthesis* / Q000737:chemistry; D002236:Carbohydrate Conformation; D004187:Disaccharides / Q000138:chemical synthesis* / Q000737:chemistry; D005688:Galactosamine / Q000737:chemistry*; D006031:Glycosylation; D009682:Magnetic Resonance Spectroscopy; D019158:N-Acetylneuraminic Acid / Q000737:chemistry*; D009844:Oligosaccharides / Q000737:chemistry; D010100:Oxygen / Q000378:metabolism; D011725:Pyridines / Q000737:chemistry; D013237:Stereoisomerism; D013696:Temperature
chemical_list: C505969:3,4-di-O-acetyl-2-azido-2-deoxy-6-O-(methyl (5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-2-nonulopyranosyl)onate)galactopyranose; D001386:Azides; D004187:Disaccharides; D009844:Oligosaccharides; D011725:Pyridines; D005688:Galactosamine; D019158:N-Acetylneuraminic Acid; D010100:Oxygen