Anomeric region

The ratio of the different isomeric products was found to vary with time, temperature, and initial concentration. This suggested that some kind of equilibration was occurring between isomers. I3C NMR spectroscopy of a reaction mixture showed, upon cooling, the reversible formation of a pair of signals in the anomeric region. These signals were ascribed to the anomeric carbon atoms of fructofuranosyl fluorides (10), which were presumed to be in equilibrium with the reactive fructofuranosyl cation, 11. 

Moreover, an absorption band near 1375 cm-i is detected and it is assigned to the CH bending vibration present in cellulose and hemicellulose chemical structures (Sim et al., 1998). The prominent band at 1044 cm-i is also associated with hemicelluloses and is attributed to the C-OH bending. Finally, a sharp band at 897 cm-i, which is typical of b-glycosidic linkages between the sugar units in hemicelluloses, was detected in the anomeric region (Sun et al., 2005). 

Conformations of mycothiol bimane (MSmB) were studied by H and 13C NMR using rotational nuclear Overhauser effect spectroscopy (ROESY) and heteronuclear single quantum correlation (HSQC) methods with expansions of the anomeric region <2003JOC3380>. NMR characterization of iV-acetyl-L-(Y)-cysteinyl monobimane and peracetylated MSmB was also published (Section 12.10.15.4) <2002JA3492>. 

Fig. 2. Simulation of the anomeric region of the H NMR spectrum of batatin I (230). The top trace is the measured 500 MHz spectrum, resolution enhanced. Actual chemical shifts are depicted along the bottom of the top plots. Below are the simulated spectra for each of the units. The descriptors denote a specific position for each sugar unit. From Escalante-Sdnchez and Pereda-Miranda (2007) with permission of the American Chemical Society (7S)...

Figure 4. (Upper) Anomeric region of the C-13 NMR spectra at 90° for dextran B-d402 (2,6-di-O-substituted branching) dextran B-1142 (3,6-di-O-substituted branching) dextran B-1142 (3,6-di-O-substituted branching) and dextran B-1526 Fraction I (4,6-di-O-substUuted branching). For each dextran the most intense resonance (99.6 ppm) represents the 6-0-substituted a-D-glucopyranosyl residue. (Lower) Anomeric region of the 90° C-13 NMR spectra for mannan Y-1842 and the 76-90 ppm region for mannan YB-1344...

Figure 2. The anomeric region of the 100 MHz NMR spectrum of D-allose in D20 (lower curve), and in 0.8 M NaCl, 0.8 M CaCl2, and 1.0 M LaCls solution in D20 (successive curves) at equilibrium...

Figure 20. 400 MHz 1H-NMR spectrum of anomeric region at 50oC (A) and proposed structure (B) of the oligosaccharaide from Aspergillus saitoi carboxypeptidase.

HSQC/HMQC can be safely employed through Ser-Hot/Ser-Ca correlation in a well-defined region (51-53 ppm) that is well separated from the anomeric region (95-105 ppm).106 The one-bond heteronuclear correlation of the 13C resonances at 46-48 ppm provides a rapid way for the unambiguous NMR assignments of glycine residues. 

The ROESY spectrum for lactose is given in Figure 5.29. Note the overall appearance in the upper part of the figure. In the lower part, the anomeric region is shown as expanded insets. The two glucose... 

MI9) (Scheme 46). The presence of two closely related isomers was indicated by H-NMR spectroscopy, which showed the presence of two doublets due to H-2 and two singlets for each aromatic proton in 211B (86MI9). Its C-NMR spectrum ruled out structure 212, since it showed a single resonance for C-3 in the anomeric region instead of the two... 

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