Carbon polysaccharide from

The pyruvic acid may also be linked to vicinal positions. When linked to 0-3 and 0-4 of a D-galactopyranosyl residue (40), the dioxolane ring becomes cw-fused. In the limited number of known examples, the absolute configuration at the acetalic carbon atom is (S), as in 40. There are some examples of tra -fused dioxolane rings, and these are more sensitive to hydrolysis with acid than the others. Thus, pyruvic acid is acetalically linked to 0-3 and 0-4 of an a-L-rhamnopyranosyl residue in the Klebsiella type 72 capsular polysaccharide, to 0-2 and 0-3 of an a-D-galactopyranosyl residue in the Streptococcus pneumoniae type 4 capsular polysaccharide, and to 0-2 and 0-3 of a S-D-glucopyranosyluronic acid residue in the Klebsiella K1 capsular polysaccharide. " In the extracellular polysaccharide from... 

An article by Barreto-Bergter (Rio de Janeiro, Brazil) and Gorin (Saskatoon, Canada) likewise invokes strong emphasis on n.m.r. methods for structure determination, in this instance by use of carbon-13 techniques in delineating the structural chemistry of polysaccharides from fungi and lichens. 

M CHjCOONa or 0.05 M EOT A, pH 5 For metal ions in the form of carbonates or adsorbed on the surface of a hardly soluble soil matrix 2 % driselase or mixture of cellulase in 10 mM Tris-HCl, pH 7.4 For peptides and polysaccharides from the cell wall... 

Figure 3 Biosynthetic pathways. (A) In the terpenoid coupling reaction, isomers of isopentenyl pyrophosphate are joined with the loss of pyrophosphate, leading to a linear intermediate that is cyclized to a terpenoid skeleton, as shown for the diterpene taxol. (B) In the polysaccharide coupling reaction, hexose and pentose monomers are joined with the loss of a nucleoside diphosphate, as shown for the epivancosaminyl-glucose disaccharide of vancomycin. (C) In the first step of the nonribosomal peptide coupling reaction, an aminoacyl adenylate is transferred to a carrier protein or thiolation domain (denoted T ) with loss of adenosine monophosphate. In the second step, this carrier protein-tethered aminoacyl group is coupled to the amine of an aminoacyl cosubstrate, forming a peptide bond, as shown for two residues in backbone of vancomycin. (D) In the polyketide coupling reaction, the loss of carbon dioxide from a two or three-carbon monomer yields a thioester enolate that attacks a carrier protein-tethered intermediate, forming a carbon-carbon bond as shown for the polyketone precursor of enterocin.

Initial enolisation of glucose yields the 1,2-enediolate. Expulsion of the 3-OH or 3-OR yields a l-aldehydo-3-deoxy-2,3-enol. This tautomerises to the ot-ketoaldehyde and addition of OH at Cl, followed by shift of HI as hydride, yields a pair of straight-chain, C2-epimeric, 3-deoxygluconic acids known as metasaccharinic acids. These are the predominant six-carbon products from the peeling reaction of 1 3-linked polysaccharides. 

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