A -Acetyl neuraminic acid

The Glaxo synthesis of zanamivir (2) started with the esterification of commercially available A-acetyl-neuraminic acid (88) with methanolic HCl to give the methyl ester as shown in Scheme 7.14 (Chandler and Weir, 1993 Chandler et ah, 1995 Patel, 1994 Weir et al., 1994). Global acetylation of all the hydroxyl groups with acetic anhydride in pyridine with catalysis by 4-(dimethylamino)pyridine (DMAP) led to the penta-acetoxy compound 89. Treatment of 89 with trimethylsilyl triflate in ethyl acetate at 52°C introduced the oxazoline as well as the 2,3-double bond to provide 86. Addition of trimethysilyl azide to the activated allylic oxazoline group led to the stereoselective introduction of azide at the C-4 position to afford 83 as in Scheme 7.13. 

A-Acetyl neuraminic acid (NANA, 0-Sialic acid, 5-acetamido-3,5-dideoxy-D-g/ycer0-D-gIacto-2-nonulosonic acid, lactaminic acid) /131-48-6] Nl 309.3, m 159°(dec), 181-... 

A-Acetyl neuraminic acid aldolase [from Clostridium perfringens, A-acetylneuraminic acid pyruvate lyase] [9027-60-5] [EC 4.1.3.3]. Purified by extraction with H20, protamine pptn, (NH4)2S04 pptn, Me2CO pptn, acid treatment at pH 5.7 and pptn at pH 4.5. The equilibrium constant for pyruvate + n-acetyl-D-mannosamine ++ /V-acetylneuraminidate at 37° is 0.64. The Km for A-acetylneuraminic acid is 3.9mM in phosphate at pH 7.2 and 37°. [Comb and Roseman Methods in Enzymology 5 391 1962). The enzyme from Hogg kidney (cortex) has been purified 1700 fold by extraction with H20, protamine sulphate pptn, (NH4)2S04 pptn, heat treatment between 60-80°, a second (NH4)2S04 pptn and starch gel electrophoresis. The Km for A-acetylneuraminic acid is 1.5mM. [Brunetti et al. JBC 237 2447 1962). 

Scheme 4.12 Glycosylation of A-acetyl-neuraminic acid (NeuSAc) by direct and indirect approaches,...

CMP-A/-Acetyl neuraminic Acid Glycoprotein Slalyltransferase (Spiegel et al., 1992)... 

Kunz, H, Waldmann, H, Directed stereoselective synthesis of a- and (i-A-acetyl neuraminic acid-galactose disaccharides using 2-chloro and 2-fluoro derivatives of neuraminic acid allyl ester, J. Chem. Soc. Chem. Commun., 638—640, 1985. 

Stmctural modification of sLe tetra- or pentasaccharide, with the goal of identifying suitable L-fucose, A -acetyl-D-glucosamine, D-galactose or A -acetyl-neuraminic acid replacements (see Section 16.4.3.2). 

Pichierri, F, Matsuo, Y, Effect of protonation of the A-acetyl neuraminic acid residue of sialyl Lewis a molecular orbital study with insights into its binding properties toward the carbohydrate recognition domain of E-selectin, Bioorg. Med. Chem. Lett., 10, 2751-2757, 2002. 

NeuNAc A-acetyl neuraminic acid (sialic acid)... 

A -Acetyl neuraminic acid aldolase [from Clostridium perfringens, Al-acetyineuraminic acid pyruvate lyase] [9027-60-5] 32,000 [EC 4.1.3.3]. Purified by extraction with H2O,... 

A -Acetyl-) neuraminic acid (27) is another important hydroxy acid in which several hydroxyl groups are available for complex-formation. 

In ketopyranoses, the reluctance of carbon substituents to become axial acts in the same direction as the anomeric effect, so that the OH-axial pyranose anomer is overwhelmingly predominant, as in fructopyranose and A -acetyl-neuraminic acid (Figure 2.19). 

Aldol reactions of this type, involving 2-acetamido-2-deoxyaldohexoses, have been studied in connection with the chemical synthesis of A -acetyl-neuraminic acid (50) and related substances, and, for this reason, the choice of the dicarbonyl compound has thus far been limited to oxalacetic acid and its esters. Oxalacetic acid condenses readily with 2-acetamido-2-deoxyaldohexoses in aqueous solution at pH 11. Under these conditions, acetamido sugars partially epimerize, and the aldol reaction takes place for both of the 2-acetamido-2-deoxyaldohexoses present. The complexity of the reaction is further increased by the formation of asymmetric centers at carbon atoms 3 and 4 of the condensation products, namely, diacids (45) and (48), and this can result in the formation of four diastereo-isomers from each sugar. The reaction using 2-acetamido-2-deoxy-o-rnannose (47) has been the one most extensively studied. In this... 

A-acetyl neuraminic acid lyase (NAL) catalyzes the reversible aldol addition of N-acetylmannosamine to pyruvate to produce A-acetylneuraminic acid, a sialic acid. Sialic acid is an essential component of complex carbohydrates which are of paramount importance as recognition signals in a variety of biological process, such as parasite invasion, infectivity and survival of the invading organism in the host. Hence, sialic acids mimetics, such as the commercial Oseltamavir, Relenza and... 

Three fractions of complex gangliosides were isolated from bovine erythrocytes. Each contained branched oligosaccharide chains and comprised 11-13 monosaccharide residues per molecule and included 1-2 units of A -acetyl-neuraminic acid. 

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