Preparation of Oligosaccharides

7-diamino-3,5,7,9-tetradeoxynonulosonic acids are stable towards hydrogen fluoride at -t- 20°. This allows easy generation of oligosaccharides having 

Other examples are some Pseudomonas aeruginosa O-specific polysaccharides containing amino and diamino derivatives of uronic acids. Thus, the polysaccharide (30) ofLanyi serotype 0 3a, 3d under the action of HF for 3 h at 20° underwent strictly selective cleavage - at the glycosidic linkages of A -acetylfucosamine, to give the trisaccharide 31 in practically quantitative yield. 

Solvolysis of the polysaccharide (32) of P. aeruginosa L nyi 0 4a, 4c with hydrogen fluoride at room temperature led to the trisaccharide figment 33 as the only oligosaccharide product. 

The different stability of the glycosidic linkage of 2-acetamido-2-deoxy-D-mannuronic acid towards hydrogen fluoride at room temperature in H. influenzae and S. pneumoniae polysaccharides on the one hand and in the N. meningitidis polysaccharide on the other, may be accounted for by the different neighboring sugar residues. 

The glycosidic linkages of A -acetylhexosamines are more stable than those of their 6-deoxy derivatives (such as A -acetylquinovosamine and A -acetyl-fucosamine). Thus, owing to the facile cleavage of the glycosidic linkages of 

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Kallin, E., Lonn, H., Norberg, T., and Elofsson, M. (1989) Derivatization procedures for reducing oligosaccharides, Part 3 Preparation of oligosaccharide glycosylamines, and their conversion into oligosaccharide-acrylamide copolymers./. Carbohydr. Chem. 8, 597-611. 

As a further illustration of the scope for use of 1,6-anhydro sugars in the preparation of uncommon sugars, the rare L-idose derivative 210 has been prepared recently and used in the preparation of oligosaccharides containing iduronic acid... 

S. David, A. Malleron, and C. Dini, Preparation of oligosaccharides with p-D-mannopyranosyl and 2-azido-2-deoxy-p-D-mannopyranosyI residues by inversion at C-2 after coupling, Carbo-hydr. Res. 788 193 (1989). 

J. E. Heidlas, K. W. Williams, and G. M. Whitesides, Nucleoside phosphate sugars Syntheses on practical scales for use as reagents in the enzymatic preparation of oligosaccharides and glycoconjugates, Acc. Chem. Res. 25 307 (1992). 

Takahashi et al.45 used a 4-hydroxybenzenesulfonate linker on Syn-Phase polystyrene Crowns to prepare glucose derivatives and macrocycles (Scheme 20). Displacement of the monosaccharide-supported Crowns 70 with nucleophiles such as azide, iodide, and acetate gave the respective 6-substituted glucose derivatives 71, 72, and 73 in excellent purities and yields. The authors suggest that this methodology could be utilized for the preparation of oligosaccharide libraries. 

Polymer-supported liquid-phase synthesis was introduced for the preparation of oligosaccharides by Douglas, Whitheld and Krepinsky [99]. In their procedure, the carbohydrate is attached to the soluble polymer, poly(ethylene glycol)monomethyl ether (PEG), and all the chemical... 

In recent years, tremendous progress has been made in the chemical synthesis of oligosaccharides. New glycosylation and protection methods resulted in new strategies and techniques for the preparation of oligosaccharides. As a result, large and complex oligosaccharides... 

The glycosyl donors illustrated in Figme 9 have been the ones most commonly employed in the preparation of oligosaccharides containing D-arabinofuranosyl residues. The vast majority of glycosidic bonds in mycobacterial arabinan are a link-... 

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