NMR spectroscopy of 13C-enriched polysaccharides:: Application of 13C-13C TOCSY to sugars of different configuration

C-13-C-13 2D TOCSY experiments were applied, with both carbon-13 and proton detection, to alleviate the problem of limited H-1-H-1 coherence transfer in certain sugars, e.g. those with the manno or galacto configuration. The C-13-C-13 couplings are not as dependent on the different sugar geometries and can be up to 50 times larger, i.e. (1)J(CC) vs. (3)J(HH). For bacterial polysaccharides, M-r ca. 10(4)-10(5), loss of magnetization can be severe owing to long delays in H-1-H-1 TOCSY experiments, and these are circumvented by applying the spin lock on the C-13 nuclei. (C) 1998 John Wiley & Sons, Ltd.