Sialic acid bonds

Sesquiterpenoid. 203, 1071 Sex hormone, 1082-1083 Sharpless, K. Barry. 734 Sharpless epoxidation, 735 Shell (electron), 5 capacity of, 5 Shielding (NMR). 442 Si prochirality, 315-316 Sialic acid. 997 Side chain (amino acid), 1020 Sigma (cr) bond, 11 symmetry of, 11 Sigmatropic rearrangement, 1191-1195... 

Hydrophilic interaction chromatography on Asahipak NH2P or Excel-pak CHA-P44 with pulsed amperometric detection has been used to fractionate malto-oligosaccharides.266 The Asahipak NH2P is a polyvinyl alcohol support with a polyamine bonded phase, and the Excelpak is a sulfonated polystyrene in the Zn+2 form. Amine adsorption of sialic acid-containing oligosaccharides was performed on a Micropak AX-5 column (Varian) using acetonitrile-water-acetic acid-triethylamine.267... 

Oxidation of polysaccharides using 10 mM or greater concentrations of sodium periodate at room temperature results in the cleavage of adjacent hydroxyl-containing carbon-carbon bonds on other sugars besides just sialic acid residues (Lotan et al., 1975). High concentrations... 

Figure 11.22 Azido-sialic acid-containing glycans can be labeled in vivo with biotin-PEG-phosphine using the Staudinger ligation reaction, which forms an amide bond.

Figure 17.19 An azido-sialic acid derivative that gets incorporated into glycans in cells can be labeled specifically with a biotin-phosphine tag using the Staudinger ligation process. The result is an amide bond linkage with the glycan.

Several enzymatic procedures have been developed for the synthesis of carbohydrates from acyclic precursors. Aldolases appear to be useful catalysts for the construction of sugars through asymmeteric C-C bond formation. 2-deoxy-KDO, 2-deoxy-2-fluoro-KDO, 9-0-acetyl sialic acid and several unusual sugars were prepared by a combined chemical and enzymatic approach. Alcohol dehydrogenases and lipases have been used in the preparation of chiral furans, hydroxyaldehydes, and glycerol acetonide which are useful as building blocks in carbohydrate synthesis. 

Asymmetric C-C bond formation is the most important and most challenging problem in synthetic organic chemistry. In Nature, such reactions are facilitated by lyases, which catalyze the addition of carbonucleophiles to C=0 double bonds in a manner that is classified mechanistically as an aldol addition [1]. Most enzymes that have been investigated lately for synthetic applications include aldolases from carbohydrate, amino acid, or sialic acid metabolism [1, 2]. Because enzymes are active on unprotected substrates under very mild conditions and with high chemo-, regio-, and stereoselectivity, aldolases and related enzymes hold particularly high potential for the synthesis of polyfunctionalized products that are otherwise difficult to prepare and to handle by conventional chemical methods. 

Stereo image of a ball-and-stick model of sialic acid bound to the active site of Tern/N9 neuraminidase. The hydrogen-bond interactions with conserved residues are shown as dotted lines. Nitrogen atoms are shaded black, oxygen atoms are shaded dark gray, and carbon atom are shaded light gray. 

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