Abstract
Ab initio, GIAO and IGLO, nuclear shielding calculations are performed on each of the four pyranose ring residues of the tetrasaccharide repeating unit in a single chain of the gellan polysaccharide, [→ 3)-
d-Glcp-(1 → 4)-β-
d-GlcpA-(1 → 4)-β-
d-Glcp-(1 → 4)-α-
l-Rhap(1
n
. The results provide an insight into the effects of the changing primary molecular electronic structure on the calculated
13C,
17O and
1H shieldings. In particular, the observed trends in the calculated isotropic (
σ
i) shielding values are rationalised withi the framework of the localised molecular orbital shielding contributions and Mulliken population analyses (MPA).