Polysaccharides tetrasaccharide repeat unit

The difficulties inherent in obtaining correct sugar analyses for a polysaccharide containing three different amino sugars are obvious. It therefore seems possible that S4 is composed of tetrasaccharide repeating-units, containing one residue each of the four different sugar components. 

Another example of O-specific polysaccharides that are assembled through the block mechanism are the polymers from Salmonella serogroups C2 and C3. Their polysaccharide chains (18) are composed97 of linear, tetrasaccharide repeating-units having abequosyl and D-glucosyl branches,... 

Synthesis of the tetrasaccharide repeating-unit of the O-specific polysaccharide from Salmonella senftenberg. Carbohydr. Res. 5 1, 269-27 1... 

Kochetkov, N.K., Torgov, V.I., Malysheva, N.N., Shashkov, A.S., and Klimov, E.M. (1980a). Synthesis of the tetrasaccharide repeating-unit of the O-specific polysaccharide from Salmonella muenster and Salmonella minneapolis. Tetrahedron 36. 1227-1230 Kochetkov, N.K., Torgov, V.I., Malysheva, N.N., and Shashkov, A.S. (1980b). Synthesis of the pentasaccharide repeating-unit of the O-specific polysaccharide from Salmonella Strasbourg. Tetrahedron 36, 1099-1105... 

The substrate, i,e. the O-antigenic polysaccharide chain, can carry several substituents on the basic tetrasaccharide repeating unit in form of D-glucose residues or O-acetyl groups (Figure 7). 

Shigella flexneri LPSs comprise a large family of interrelated O-polysaccharide structures, the simplest of which belongs to the Y variant polysaccharide (Table 3). This has a tetrasaccharide repeating unit containing three L-rhamnose residues and... 

Figure 6. The tetrasaccharide repeating unit of Klebsiella K8 polysaccharide showing the atom labeling. The residue A is ft-D-glucose B is a-D-galactose C is /3-D-galactose and D is a-D-glucuronate.

In addition, to understand the polysaccharide biosynthesis of a species-specific CPS in different Campylobacter species, 6-O-methyl-D-g/ycero-a-L-g/Mco-heptopy-ranose—one of the residues of the tetrasaccharide repeating unit of the CPS of Campylobacter jejuni NCTC 11168—was synthesized [134],... 

Knowledge of the chemical repeating pattern is a prerequisite to analysis of the diffraction patterns from polysaccharides. Among the complex polysaccharides studied thus far, heparin has presented the most problems. Nieduszynski and Atkins22 -24 previously interpreted the data by using a tetrasaccharide repeat unit for heparin they have now taken the repeat unit to be a disaccharide, composed of substituted 2-amino-2-deoxy-D-glucose and L-iduronate residues.25 In a re-... 

Selective benzoylation (and allylation) of methyl (and benzyl 4-O-benzyl-a-L-rhamnopyranoside (4) has been studied by phase-transfer catalysis and by activation via the tributyl stannate. The former reaction gave the 2,4-dibenzyl ether (5) in high yield, whereas the latter process gave mainly the 3,4-diether (6). An alternative means of obtaining the 2,4-diether (5) involved selective tritylation to give (7) followed by benzylation and removal of the trityl group. These dibenzyl ethers have been employed in the synthesis of the tetrasaccharide repeating unit of the immunodeterminant of Klebsiella serotype K36 polysaccharide. Similar results have been recorded for the selective benzylation of other 4,6-blocked a-mannosides. The syntheses of 3-O-benzyl-D-ribose, 2-0-benzyl-D-ribose, and l,6-anhydro-2,3,2, 4-tetra-0-benzyl-jS-lactose have been recorded. The latter was employed in the synthesis of lacto-A -tetraose. ... 

Czs-linked tetrasaccharide repeating unit of the capsular polysaccharide of Bacillus stearothermophilus was synthesized from suitably protected... 

Methylation analysis. Smith degradation, and H n.m.r. spectroscopy of Klebsiella 6412 polysaccharide and of the degraded polysaccharide have identified the tetrasaccharide repeating unit (14)A Studies of the cross-reactions between Klebsiella K polysaccharides and zeati-Klebsiella antibodies in sera have been reported. ... 

The details of the synthetic approach we have adopted for the preparation of all possible di- and trisaccharide sequences of the Y polysaccharide repeating unit have been published (16-19), together with the syntheses of two of the four possible tetrasaccharides (19,20). The synthesis of a third tetra-saccharide sequence not previously reported is described below. 

---