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Carbohydrates anomeric region

Figure 3 Stack plot of the H NMR spectra (carbohydrate region) of an alginate sample acquired without (a) and with water suppression (b, c and d). The zg spectrum is vertically scaled by a factor of 4.5 (receiver gain adjustment). The relative areas of the signals in the anomeric region (A, B and C) and the M/G ratios calculated from these are indicated at each spectrum. Figure 3 Stack plot of the H NMR spectra (carbohydrate region) of an alginate sample acquired without (a) and with water suppression (b, c and d). The zg spectrum is vertically scaled by a factor of 4.5 (receiver gain adjustment). The relative areas of the signals in the anomeric region (A, B and C) and the M/G ratios calculated from these are indicated at each spectrum.
The anomeric-carbon region shows six peaks, numbered in Fig. 4. Peak 1 (at 103.6 p.p.m.), which arises from 25 5 carbon atoms, can be assigned to the anomeric-carbon atoms of a-D-mannopyranosyl units, having free hydroxyl groups at C-2, that are involved in glycosidic linkages to 0-2 or 0-3 of other a-D-mannopyranosyl residues.15 Peak 2 (at 102.5 p.p.m.) probably arises from 2-O-substituted a-D-mannopyrano-syl units involved in linkages to 0-2 or 0-3 of other a-D-mannopyranosyl units (internal carbohydrates)15 and also to the anomeric carbon atom of the a-D-mannopyranosyl residue linked to L-threonine.19 Peak 3 (101.8 p.p.m.) arises from the a-D-mannopyranosyl unit linked to L-ser-ine.19... [Pg.43]

Table XVIII contains the 13C-n.m.r.-spectral data for the model compounds a,/ -Araf — Hyp and a,/ -Ara/— Hyp. The assignments of Qfi and Cs of Hyp were readily obtained19 by comparison with 13C data for L-Hyp in the free amino acid form and for L-Hyp residues of peptides.109 The chemical shift of C 5 was, as expected, 7-8 p.p.m. downfield from the values reported for nonglycosylated L-Hyp. The chemical shifts of C and Cy appeared in the same region as carbohydrate resonances and were therefore identified through their chemical shift-pH dependence.19 The chemical shift of the / -anomeric carbon atom in compound 60 is rather up-field, in agreement with a syn orientation for the C-1 - O-1 and... Table XVIII contains the 13C-n.m.r.-spectral data for the model compounds a,/ -Araf — Hyp and a,/ -Ara/— Hyp. The assignments of Qfi and Cs of Hyp were readily obtained19 by comparison with 13C data for L-Hyp in the free amino acid form and for L-Hyp residues of peptides.109 The chemical shift of C 5 was, as expected, 7-8 p.p.m. downfield from the values reported for nonglycosylated L-Hyp. The chemical shifts of C and Cy appeared in the same region as carbohydrate resonances and were therefore identified through their chemical shift-pH dependence.19 The chemical shift of the / -anomeric carbon atom in compound 60 is rather up-field, in agreement with a syn orientation for the C-1 - O-1 and...
Fig. 1 also may be used to note some general characteristics of C spectra of carbohydrate polymers ( -11) Chemical shifts of anomeric carbons (C-l), in the region of 100-110 p.p.m., are typically well separated from other signals. As compared with C-l of the related monosaccharides (12-15)j the anomeric carbon is strongly deshielded (commonly by 7-10 p.p.m.) through glycoside formation (9)> i.e., by the change from 0-H to an 0-C bond. [Pg.123]


See other pages where Carbohydrates anomeric region is mentioned: [Pg.8]    [Pg.14]    [Pg.21]    [Pg.28]    [Pg.40]    [Pg.41]    [Pg.17]    [Pg.20]    [Pg.14]    [Pg.669]    [Pg.119]    [Pg.669]    [Pg.8]    [Pg.14]    [Pg.21]    [Pg.28]    [Pg.40]    [Pg.41]    [Pg.103]    [Pg.15]    [Pg.119]    [Pg.473]    [Pg.11]    [Pg.17]    [Pg.208]    [Pg.59]    [Pg.139]    [Pg.460]    [Pg.462]    [Pg.92]    [Pg.28]    [Pg.614]    [Pg.205]    [Pg.228]    [Pg.68]    [Pg.37]    [Pg.1622]    [Pg.2508]    [Pg.17]    [Pg.24]    [Pg.27]    [Pg.280]    [Pg.670]    [Pg.11]    [Pg.17]   
See also in sourсe #XX -- [ Pg.11 , Pg.19 ]




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Anomeric region

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