title: 1,3,4,6-Tetra-O-acetyl-2-chloroacetamido-2-deoxy-beta-D-glucopyranose as a glycosyl donor in syntheses of oligosaccharides.
abstract: 1,3,4,6-Tetra-O-acetyl-2-chloroacetamido-2-deoxy-beta-D-glucopyran ose was tested as a glycosyl donor for oligosaccharide synthesis via a ferric chloride-catalyzed coupling reaction. Glycosyl acceptors tried (6 in all) were O-benzyl-protected D-galactosides having free OH groups at positions 3 and 4, respectively, and similarly protected glycosides of D-glucose and 2-acetamido-2-deoxy-D-glucose unsubstituted on O-4. Existing syntheses of all the acceptors were improved, in four instances by exploitation of Garegg and Hultberg's cyanoborohydride procedure for the conversion 4,6-O-benzylidene----6- O-benzyl [Carbohydr. Res., 93 (1981) c10-c11; 108 (1982) 97-101]. Good to excellent yields of beta-linked disaccharides were obtained from the galactoside and glucoside acceptors, but with allyl 2-acetamido-3,6-di-O-benzyl-2-deoxy-alpha-D-glucopyranoside, stereoselectivity was lost (alpha:beta-ratio 1:2). Allyl and benzyl 2-acetamido-3,6-di-O-benzyl-2-deoxy-beta-D-glucopyranosides gave, respectively, the allyl and benzyl beta-glycosides of the donor as major products. A mechanism is proposed for this transglycosidation reaction. The N-chloroacetyl groups in the disaccharide products were readily converted into N-acetyl by reduction with zinc-acetic acid.
authors.affiliation: Department of Biochemistry, University of Wisconsin-Madison 53706.
authors.forename: F
authors.initials: F
authors.lastname: Dasgupta
authors.forename: L
authors.initials: L
authors.lastname: Anderson
mesh_terms: D002240:Carbohydrate Sequence; D055598:Chemical Phenomena; D002621:Chemistry; D006031:Glycosylation; D009682:Magnetic Resonance Spectroscopy; D008722:Methods; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009844:Oligosaccharides / Q000138:chemical synthesis*
chemical_list: D009844:Oligosaccharides