5,7-diamino-3,5,7,9-tetradeoxynon-2-ulosonic acids

DIAMINO-3,5,7,9-TETRADEOXYNON-2-ULOSONIC ACIDS IN BACTERIAL GLYCOPOLYMERS CHEMISTRY AND BIOCHEMISTRY... 

A new class of ald-2-ulosonic acids, 5,7-diamino-3,5,7,9-tetradeoxynon-2-ulosonic acids, reported as sialic acids of a new type, was discovered in 1984.9 Members of this class contain an additional amino group at C-7, additional deoxygenation at C-9 (methyl group) and may exhibit configurational differences as compared with neuraminic acid. Unlike sialic acids, the new class of ald-2-ulosonic acids appears to be unique to microorganisms. 

The present article focuses on the occurrence and characterization of derivatives of 5,7-diamino-3,5,7,9-tetradeoxynon-2-ulosonic acids and presents experimental approaches used to identify them and to elucidate the structures of the bacterial polysaccharides that contain the nonulosonic acids. Recent data on the biosynthesis of these sugars and their role in immune recognition and epitope specificity of bacterial glycopolymers are discussed. 

Occurrence of Derivatives of 5,7-Diamino-3,5,7,9-tetradeoxynon-2-ulosonic Acids (1-4) in Bacterial Polysaccharides... 

In contradistinction to sialic acids,1 2 little is known about biosynthesis of 5,7-diamino-3,5,7,9-tetradeoxynon-2-ulosonic acids. Some data are available on biosynthesis of derivatives of pseudaminic acid16 and legionaminic acid47 in human pathogens C. jejuni and L. pneumophila. 

LPSs carry the major immunogenic determinants on the cell surface of Gram-negative bacteria and, in many instances, serve as the basis for their serological classification. In this section, contribution of LPSs that contain 5,7-diamino-3,5,7,9-tetradeoxynon-2-ulosonic acids to the immunospecificity and serological classification of two human pathogens, viz. L. pneumophila and P. aeruginosa, are reviewed. 

The main approaches used for identification of natural isomers of 5,7-diamino-3,5,7,9-tetradeoxynon-2-ulosonic acids and determination of structures of bacterial poly- and oligosaccharides-containing derivatives of these sugars were H and 13C NMR spectroscopy. This could be applied to both intact natural glycopolymers and carbohydrate portions obtained after delipidation of LPS as well as to oligosaccharide fragments and... 

By analogy with the synthesis of /V-acetylneuraminic acid,63 di-A-acetyl derivatives of 5,7-diamino-3,5,7,9-tetradeoxynon-2-ulosonic acids could be obtained by condensation of 2,4-diacetamido-2,4,6-trideoxyhexoses with oxaloacetic acid under basic conditions. Four chiral centers in the C precursors, C-2 C-5, correspond to the centers C-5-C-8 in the target C9 products, and the fifth asymmetric center, C-4, is formed upon condensation. At present, derivatives of twelve 2,4-diamino-2,4,6-trideoxy-hexoses with the d-gluco, o-manno, L-allo, r>-galacto, D- and L-altro, D- and L-talo, D- and l-gulo, D- and L-ido configurations have been prepared by multistep chemical syntheses.11,17,18,64,65... 

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