The present study has given a quantum chemical analysis of the
influence of main-chain conformation and the number of the
hydrogen bonds. The analysis of the DFT data resulted in a much
more refined picture of 1H chemical shifts vs structure firstly.
Supposing that both the two conformations, dihedral angle of the
main-chain that was fixed and that of was not fixed, are likely to be
found in real structures. This quantum chemical calculation
method can be used to investigate the special conformation of the
molecules with hydrogen bond interactions. The chemical-shift and
conformation predicted by quantum chemical calculations were
confirmed by solid-state NMR SUPER experiments