title: Synthesis of 1,2- and 1,3-N-Linked Disaccharides of 5-Thio-alpha-D-mannopyranose as Potential Inhibitors of the Processing Mannosidase Class I and Mannosidase II Enzymes.
abstract: The syntheses of S/N acetal heteroatom analogues of 1,2- and 1,3-linked mannopyranose disaccharides are described. The compounds are analogues of the Man-alpha-(1-->2)-Man and Man-alpha-(1-->3)-Man disaccharide components of oligosaccharides found in N-glycoproteins that are cleaved by trimming mannosidases during glycoprotein processing. Glycosylamine formation, without the necessity of hydroxyl group protection, proceeded through acid-catalyzed condensation reactions of 5-thio-D-mannose with either methyl 2-amino-2-deoxy- or 3-amino-3-deoxy-alpha-D-mannopyranoside to give methyl 2-amino-2-deoxy-2-N-(5-thio-alpha/beta-D-mannopyranosyl)-alpha-D-mannopyranoside (2) or methyl 3-amino-3-deoxy-3-N-(5-thio-alpha/beta-D-mannopyranosyl)-alpha-D-mannopyranoside (3), respectively. The superiority of mercuric chloride over acetic acid as a catalyst for this reaction is reported. Acetylation of the anomeric mixtures gave the heptaacetates from which the major beta'-isomers could be separated by chromatography and/or crystallization.
authors.affiliation: Department of Chemistry and Protein Engineering Network of Centres of Excellence, Simon Fraser University, Burnaby, B.C., Canada V5A 1S6.
authors.forename: Blair D.
authors.initials: BD
authors.lastname: Johnston
authors.forename: B. Mario
authors.initials: BM
authors.lastname: Pinto