Carbon-13 NMR Spectra of Sodiumd-Gluco- andd-Galactopyranuronates in the Presence of Lanthanide Ions

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Abstract
Carbon-12 NMR spectra of sodium D-gluco- and D-galactopyranuronates were measured in the presence of lanthanum, europium, praseodymium or neodymium ion in deuterium oxide. The lanthanide-induced shifts of all the carbon signals were divided into 3 components based on complex-formation, contact and pseudocontact effects. The last effects on C-1 in the .alpha.-anomers were exceedingly greater than those in the corresponding .beta.-anomers. Carbon-13 spin-lattice relaxation times and their reduction induced by gadolinium ion were also measured and the binding sites of the ion were estimated, which showed marked differences between the 2 anomers and suggested the formation of bidentate complexes, involving linkages to the ring and the carboxyl O only between the .alpha.-anomers and the lanthanide ions.