NMR spin–spin coupling constants (scalar couplings, J-couplings) are highly abundant in saccharides, with multiple values often reporting on the same structural domain (redundancy). While conventional analyses of J-couplings typically involve studies of these parameters in relation to individual structural elements, future treatments are more likely to involve simultaneous analyses of large numbers of redundant (and in some cases correlated) J-couplings sensitive to multiple structural domains, providing a more complete appraisal of local molecular structure in solution. These analyses require quantitative relationships between J-couplings and saccharide structure. This chapter provides a detailed look at structural information encoded in one-bond (1J), two-bond (2J), three-bond (3J), four-bond (4J), and dual pathway (2+3J, 3+3J) scalar couplings involving hydrogen and carbon as coupled nuclei in saccharides. Experimental and computational data are integrated to illustrate correlations between saccharide structure, J-coupling magnitude and J-coupling sign. Topics ranging from selective isotopic labeling to enable J-coupling measurements, experimental methods to determine J-coupling magnitudes and signs, and the effects of specific types of molecular motions on the behaviors of saccharide J-couplings are treated. While work published over the past fifteen years comprise the main discussion, new data are included to augment or refine prior findings, notably on long-range 4JHH values in aldopyranosyl rings and across O-glycosidic linkages, and J-couplings pertinent to conformational analyses of glycosidic linkages.

MA’AT analysis has been applied to methyl β-d-ribofuranoside (3) and methyl 2-deoxy-β-d-erythro-pentofuranoside (4) to demonstrate the ability of this new experimental method to determine multi-state conformational equilibria in solution. Density functional theory (DFT) was used to obtain parameterized equations for >20 NMR spin-coupling constants sensitive to furanose ring conformation in 3 and 4, and these equations were used in conjunction with experimental spin-couplings to produce unbiased MA’AT models of ring pseudorotation. These models describe two-state north–south conformational exchange consistent with results obtained from traditional treatments of more limited sets of NMR spin-couplings (e.g., PSEUROT). While PSEUROT, MA’AT, and aqueous molecular dynamics models yielded similar two-state models, MA’AT analysis gives more reliable results since significantly more experimental observables are employed compared to PSEUROT, and no assumptions are needed to render the fitting tractable. MA’AT models indicate a roughly equal distribution of north and south ring conformers of 4 in aqueous (2H2O) solution compared to ∼80% north forms for 3. Librational motion about the mean pseudorotation phase angles P of the preferred north and south conformers of 3 in solution is more constrained than that for 4. The greater rigidity of the β-ribo ring may be caused by synergistic stereoelectronic effects and/or noncovalent (e.g., hydrogen-bonding) interactions in solution that preferentially stabilize north forms of 3. MA’AT analysis of oligonucleotides and other furanose ring-containing biomolecules promises to improve current experimental models of sugar ring behavior in solution and help reveal context effects on ring conformation in more complex biologically important systems.