7-0-Acetylneuraminic acid

Commercial A -acetylneuraminic acid aldolase from Clostridium perfringens (NeuAcA EC 4.1.3.3) catalyzes the addition of pyruvate to A-acetyl-D-mannosamine. A number of sialic acid related carbohydrates are obtained with the natural substrate22"24 or via replacement by aldose derivatives containing modifications at positions C-2, -4, or -6 (Table 4)22,23,25 26. Generally, a high level of asymmetric induction is retained, with the exception of D-arabinose (epimeric at C-3) where stereorandom product formation occurs 25 2t The unfavorable equilibrium constant requires that the reaction must be driven forward by using an excess of one of the components in order to achieve satisfactory conversion (preferably 7-10 equivalents of pyruvate, for economic reasons). 

Table 4. IV-Acetylneuraminic Acid Aldolase Catalyzed Preparative Aldol Additions with Pyruvate...

Deoxy-D- /rce/ o-D- a/ac7i7-nonulosonie Acid (KDN) V-Acetylneuraminic Acid Aldolase Catalyzed Preparative Aldol Additions with Pyruvate Typical Procedure27 ... 

N-Acetylneuraminic acid aldolase (or sialic acid aldolase, NeuA EC 4.1.3.3) catalyzes the reversible addition of pyruvate (2) to N-acetyl-D-mannosamine (ManNAc (1)) in the degradation of the parent sialic acid (3) (Figure 10.4). The NeuA lyases found in both bacteria and animals are type I enzymes that form a Schiff base/enamine intermediate with pyruvate and promote a si-face attack to the aldehyde carbonyl group with formation of a (4S) configured stereocenter. The enzyme is commercially available and it has a broad pH optimum around 7.5 and useful stability in solution at ambient temperature [36]. 

Influenza virus sialidase (Fig. 2) is a tetrameric glycoprotein consisting of four identical subnnits (Colman and Ward 1985), and acts as a glycohydrolase that removes a-ketosidically linked terminal AT-acetylneuraminic acid residues from gly-coconjugates. 

Nohle U, Beau JM, Schauer R (1982) Uptake, metabolism and excretion of orally and intravenously administered, double-labeled A-glycoloylneuraminic acid and single-labeled 2-deoxy-2,3-dehydro-A-acetylneuraminic acid in mouse and rat, Eur J Biochem 126 543-548 Oxford J (2005) Oseltamivir in the management of influenza. Expert Opin Pharmacother 6 2493-2500... 

Ryan DM, Ticehurst J, Dempsey MH (1995) GG167 (4-guanidino-2,4-dideoxy-2,3-dehydro-iV-acetylneuraminic acid) is a potent inhibitor of influenza virus in ferrets, Antimicrob Agents Chemother 39 2583-2584... 

Figure 24-9. Biosynthesis of gangliosides. (NeuAc, W-acetylneuraminic acid.)...

NeuAc, N-acetylneuraminic acid Cer, ceramide Gic, giucose Gai, gaiactose. -p, site of deficient enzyme reaction. 

V-Acetylneuraminic acid is a common group in glycoproteins, and it contains both the amide and carboxyl chromophores. As shown in formula 11, this nine-carbon sugar derivative has an equatorial amido group on C-5 and both a hydroxyl group and a carboxyl group on the anomeric carbon atom. 

The c.d. spectra of a number of other derivatives have been measured as models for the linkages found in oligomers. Spectra of the methyl a-and )8-D-ketopyranosides of N-acetylneuraminic acid are given in Fig. 29. They do not differ substantially from the c.d. spectra for the fundamental sugars, except that the a-ketopyranoside has a positive c.d. band of low intensity at 250 nm. These types of bands occur from time to time for still obscure reasons, as discussed for carboxyl derivatives. 

The c.d. spectra are also available for a few oligosaccharides that contain N-acetylneuraminic acid. " These spectra depend on the intersaccharide linkages and the state of ionization of the carboxyl group, but no systematic scheme has yet been set up to derive configurational information from the c.d. spectra. Of particular interest is the c.d. spectrum of beef ganglioside, which fully differentiates the amide mr, amide tttt, and carboxylate nir c.d. bands. 

IonPac KC-811 column separated the labile compounds N-acetylneuraminic acid and N-glycolylneuraminic acid released by mild acid hydrolysis of bovine vitronectin.245 Sialic acid is extremely labile to conditions of handling and must be released by mild acid hydrolysis.246 Derivatization with phe-nylisothiocyanate and separation by reversed phase chromatography was found useful in analysis of hexosamines from gastric mucosa.247 A review on separation of sugars and other carbohydrates which covers many important aspects is available.248... 

Ogawa, H. K., Takeuchi, Y., Uchibori, H., Matsumoto, I., and Seno, N., Determination of N-acetylneuraminic acid and N-glycolylneuraminic acid in glycoproteins by high-performance liquid chromatography without derivatization, /. Chromatogr., 612, 145, 1993. 

Thus, an alkene can be considered as a masked ketone that can be unmasked by ozonolysis. This is illustrated by the synthesis of N-acetylneuraminic acid via the ozonolysis of the precursor acrylic acid in THF/aqueous media (Eq. 3.22). The use of aqueous media facilitated the solubility of the polyhydroxyacids.92... 

Phosphonic acid analogues 8.2 and 8.3 of both KDN and N-acetylneuraminic acid have been synthesized using the indium-mediated coupling of the lower carbohydrates with dimethyl 3-bromopropenyl-2-phosphonate (8.4) in water (Scheme 8.9).124... 

C H19N09-2H20 5-Acetamido-3,5-dideoxy-D-gh/eero-/ -D-galacto-nonulopyran-osonic acid, dihydrate (N-acetylneuraminic acid, dihydrate) (sialic acid, dihydrate) SIALAC 31 350... 

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