Amylose carbon-13 signals

This observation is very similar to the downfield displacements of C-1 and C-4 carbons (in the glucosidic linkages) of cyclodextrins (1.6-2.0 and 2.9 ppm, respectively) compared with those of the linear (l-wl)-a-D-glucans such as amylose (30). In the formers,it appears that no overall internal rotation around the C-1-0 and C-4-0 linkages is allowed because of its cyclic structure. In a similar manner, the C-1 and C-3 signals, which exhibit the conformation-dependent downfield displacements observed in the gel state, can be ascribed to certain ordered conformations in which only a slight oscillation around the favored dihedral angle around the... 

The proton-decoupled C-NMR spectrum of carbohydrates gives a signal for each of the specific types of carbons present. For highly asymmetric carbohydrate units, this usually means a signal for each of the carbons in the asynmietric unit. This has been demonstrated for a number of saccharides, such as amylose [40], cyclomaltodextrins [41], dextrans [42], and many others [18]. It is most clearly demonstrated for sucrose in which 12 distinct signals are produced, one for each of the 12 carbons (see Fig. 12.4A). 

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