Neuraminic acid spectrum

Fig. 3. Top Resolution-enhanced 600 MHz H NMR spectrum of the octasaccharide repeating unit from Hafnia alvei strain 2 O-specific polysaccharide, (a)-(g) 500 MHz ID TOCSY subspectra with selective excitation of the respective anomeric proton resonances, (h) ID TOCSY subspectrum with the H3eq resonance of the neuraminic acid residue selectively excited. (Reproduced (adapted) with permission from Gamian et al. [25J. Copyright 1991...

Sewell AC, Poets CF, Degen I, Stoss H, Pontz BF (1996) The spectrum of free neuraminic acid storage disease in childhood clinical, morphological and biochemical observations in three non-Finnish patients. Am J Med Genet 63 203-208... 

Natural sialic acids (Schauer 1982 1991) are derivatives of 5-amino-3,5-dideoxy- D-glycero-D-galacto-nonu osonic acid 12.1. This awkward name has been replaced by neuraminic acid . The most common derivative is N-acetyl-neuraminic acid 12.2 whose configuration is easy to memorize because, in the Fischer representation, 12.3, it is presented as an aldolic condensation product of N-acetylmannosamine (2-acetamido-2-deoxy-D-mannose) and pyruvic acid. When the expression sialic acid is used without any other precision, it is in reference to derivative 12.2. It exists in the free state or glycosidated in the d-conformation, which allows an equatorial disposition of the three-carbon side chain. Structure 12.2 represents the stable /3-anomer of the free sugar with an axial anomeric hydroxyl group and all-equatorial non-anomeric substituents. An X-ray spectrum of this crystallized /3- anomer confirms this conformation and reveals, moreover, that the side chain has the zig-zag conformation with two... 

The n.m.r. spectrum of the a-anomer of N-acetyl-D-neuraminic acid was obtained by enzymic cleavage of the glycosyl azide in the... 

In di-O-acetylated neuraminic acids the effects of 0-acetylation on the chemical shifts of skeleton protons are composed of the individual contributions of each O-acetyl group. Apparently, the induced shifts are additive. This is a general phenomenon, which can be illustrated for the peracetylated neuraminic acid. The IH-NMR spectrum of this compound is shown in Fig. 4.The resonance positions of H5, H6, H7, H8, H9, and H9 can be estimated on the basis of the presumed a-and -effects of 0-acetylation at position C4, Cl, C8, and C9. 

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