N-Acylneuraminic acid

Nevertheless, chemical characterization of the first gangliosides isolated by these methods led to the identification of their constituent parts. Thus, on hydrolysis, sphingosine, fatty acids, N-acylneuraminic acid, and sugars were obtained. 

In gangliosides, the N-acylneuraminic acids are in a-D anomeric (69) conjugation with hexopyranosides, as already mentioned, and are split off enzymically with neuraminidase.198... 

Synthetic alkyl and aralkyl glycosides of N-acylneuraminic acid, obtained by the method of Koenigs and Knorr,191 are split with neuraminidase, like the natural glycosides of N-acylneuraminic acid. In contrast, the /3-D anomers (70), obtained from N-acylneuraminic acid and the appropriate alcohol in the presence of hydrogen ion, are resistant to neuraminidase.191,199 200... 

Table 1. Survey of alkyl (aryl) oL-glycosides of N-acylneuraminic acid(s) (methyl esters)...

Deoxy-2,3-dehydro-N-acylneuraminic acids have been applied in several competitive inhibition studies with neuraminidases from different sources (see for instance Meindl and Tuppy 1969b, Meindl et al. 1971, 1974, Palese and CoMPANS 1976, Veh and Schauer 1978, Kumar et al. 1981). 

Fig. 4. Survey of the selected fragment ions A-H worked out for trimethylsilylated (O-acylated) N-acylneuraminic acid methyl ester(s) (methyl glycosides) and for (partially) O-methylated N,N>acetyl,methyl-neuraminic acid methyl ester methyl glycosides. Partially O-methylated compounds are trimethylsilylated or acetylated.

Analysis of (0-Acylated) N-Acylneuraminic Acids Isolated from Biological... 

In Table 2 a series of (0-acylated) N-acylneuraminic acids isolated from various biological sources is presented (see also chapter B and C). These sialic acids have been analyzed by g.l.c./m.s. after esterification with diazomethane and trimethylsilylation (section II. 3) the Table includes relative retention times of the derivatives on g.l.c. and mje values of the fragment ions A-G. As was mentioned earlier, sialic acids predominantly occur in the p-anomeric form. However, on 3.8% SE-30 the a-anomer could sometimes be detected separately from the p-anomer (in most cases as a small shoulder). Mass spectra are depicted in Figs. 2 and 5-17. 

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