Hexasaccharides

Maltotriose is effective as a side-chain donor and acceptor in the presence of a Pseudomonas isoamylase and gives a set of 6- -a-malto- 

Two impressive reports from T. Ogawa s group describe the rational synthesis of a-cyclodextrin, i, e. the cyclic a-(l - 4) linked D-glucose hexamer. B-Glycosyl fluoride derivatives in the presence of tin(II) chloride and silver triflate were employed for the glycoside bond formations. The same group has described the 

The further, branched D-hexose-based hexasaccharides (8), (9 R = B-D-G1cNAc )and (10 R = have been prepared. 

As has become customary in these volumes, an abbreviated method is now used for representing higher saccharides. Sugars will be numbered as follows, and linkages will be indicated in the usual way  

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Figure C2.4.13. Thiol-tenninated hexasaccharide, where acetoxy groups can be replaced by hydroxyl groups, botlr before and following adsorjDtion [221],...

A hydrolyzed cereal soHd, predominately a hexasaccharide, is used in high pH lime muds for reducing the yield point and gel strength (67). This additive has been used in systems treated with both sodium hydroxide and potassium hydroxide in addition to other additives common to lime muds (68). A second viscosity-reducing additive used in lime muds is a graft copolymer of acryflc acid and calcium flgnosulfonate (69). Both of these materials are used at levels of 6—17 kg/m (2—6 lb /bbl). 

Li YF, Liu YQ, Ming Y, et al. The cytoprotective effect of inulin-type hexasaccharide extracted from Morinda officinalis on PC 12 cells against the lesion induced by corticosterone. Life Sci 2004 75 1531-1538. 

Im einzelnen wurden von R. Kuhn, H. H. Baer und A. Gauhe aus dem Oligosaccharid-Gemisch funf Komponenten in reiner Form isoliert. Es handelt sich um ein Trisaccharid, ein Tetrasaccharid, zwei isomere Pentasaccharide und ein Hexasaccharid (140), (143), (145), (146). 

The structure of S10A has been investigated by Baddiley and coworkers.34,35 The polysaccharide is composed of D-galactose, 2-ace-tamido-2-deoxy-D-galactose, ribitol, and phosphate in the molar proportions 4 1 1 1. A hexasaccharide and its N-deacetylated derivative were obtained from S10A by treatment first with base and then... 

The phosphate of ethylene glycol must derive from the ribitol phosphate moiety, which consequently is phosphorylated at a primary position, assumed to be 0-5 of (pro-D)-ribitol for biosynthetic reasons. In the proposed structure for the S10A repeating-unit (14), the anomeric natures of the sugar residues were not determined. The optical rotations of S10A and the hexasaccharide, [a]D +12° and +11°, respectively, indicate that they contain both a- and /3-D-linked sugar residues. 

Acid hydrolysis of the basic hexasaccharide yielded the disaccharide 31. Its mobility in paper chromatography lay between those of the corresponding (1 — 3)-linked (from S10A) and /3-(l — 6)-linked (from S29) isomers, which is why it was assumed to be (1 — 4)-linked. The (1 — 2)-linked isomer was excluded, as the D-galactose residue that is part of 31 carries a D-galactopyranosyl group linked to 0-2 in the original polysaccharide, as will be discussed. 

In the furanoside field, the introduction of the last two P-arabino units of a hexasaccharide motif from a bacterial cell wall arabinogalactan was achieved by the sulfoxide method with stereocontrol achieved because of the presence of the 2,3-anhydro group (Scheme 4.62) [368], More recently, the direct stereocontrolled synthesis of arabinofuranosides has been achieved by the sulfoxide method with the aid of a 3,5-0-(di-tert-butylsilylene)-protected donor [369]. 

One key NMR-based study has focused on the evaluation of the dynamic properties of heparin-like hexasaccharides.20 The analysis of Tj, T2 and NOE 13C-NMR data of biologically active synthetic compounds has shown that the sulphation pattern strongly influences the internal dynamics, and supports the importance of the GAGs flexibility on the selectivity of the interaction with fibroblast growth factors. 

Comparison of the H N.m.r. Chemical Shifts (p.p.m. from 4,4-Dimethyl-4-silapentane-l-sulfonate at 295 K) of a Tetrasaccharide and Related Hexasaccharide from Meconium Glycoproteins (73-75)... 

The versatility of this approach was demonstrated in the synthesis of a variety of oligosaccharides (Scheme 2.7). The synthesis of hexasaccharide 30 (Scheme 2.8) exemplified the use of a glucal acceptor with a secondary alcohol (27) as well as the use of a disaccharide acceptor such as 29. These typical, varied systems can be included in the protocol without complications. 

Scheme 2.8 Solid-phase synthesis of a linear hexasaccharide.

SOLID-PHASE SYNTHESIS OF THE HEXASACCHARIDE GLOBO-H ANTIGEN PROGRESS AND LIMITATIONS... 

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