Sialic acid naturally occurring

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). 

The use of S-2-phenylselenopropanal in the synthesis of the naturally occurring (8R) antipode of the title compound is described. This chemistry was adapted to achieve a total synthesis of a sialic acid glycoside in a stereospecific fashion. 

Naturally occurring oligosaccharides have also been isolated by gel chromatography. Ohman and Hygstedt94 have reported the isolation, from colostrum, of sialic acid oligosaccharides, including di-O-sialoyl-lactose [0-A/-acetylneuraminoyl-(2 — 8)-0-(N-acetylneur-... 

Sialic acid occurs naturally as both the N-acetylated and the N-glycoloylated form, the proportion in a given environment being different from one species to another.316 Oxidation of the acetyl group to the glycoloyl group occurs after the formation of 2-acetamido-2-deoxy-D-glucose.317... 

Great progress in our knowledge about sialic acids was made with the aid of gas-liquid chromatography (g.l.c.), mass spectrometry (m.s.), and n.m.r. spectroscopy. Structural analysis of the many different N- andO-acylated Neu derivatives occurring in Nature will be described in Sections IV,5 and 6. 

Nothing is yet known concerning the formation of lactvl groups found at 0-9 of sialic acids from different sources, reported in Section II. This is also true of the biosynthesis of methyl ether and sulfuric ester groups occurring in some natural sialic ac ids. 

C. Aug6, S. David, C. Gautlteron, A. Malleron, and B. Cavayd, Preparation of six naturally occurring sialic acids with immobilized acylneuraminate pyruvate lyase, New J. Chem. 72 733 (1988). 

In continuing with this section, we will highlight a further class of compounds, namely the carba-analogues of naturally occurring sialic acid, which represent a class of potential inhibitors of viral neuraminidase enzymes [63]. 

Burke and co-workers developed a desymmetrization RCM approach to the naturally occurring deaminated sialic acid KDN (Scheme 65) that was also applied to the preparation of N-... 

A number of the naturally occurring sialic acids, in particular the 0-acetylat-ed Neu5Ac derivatives, have been prepared by manipulation of NeuSAc. Deri-... 

Sialic acid is the general name of a mily of nine-carbon sugars, which are N- and 0-acyl derivatives of neuraminic add, 5-amino-3,5-dideoxy-D-gi ero-D-ga/ac/o-2-nonulopyranosic add such as 5-N-acetylneuraminic acid (NeuSAc, 1) which is the most natural occurring sialic add [1]. 

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