[C-13]-ENRICHED METHYL ALDOPYRANOSIDES - STRUCTURAL INTERPRETATIONS OF C-13-1H SPIN-COUPLING CONSTANTS AND H-1 CHEMICAL-SHIFTS

A series of methyl D-aldopentopyranosides and D-aldohexopyranosides having different configurations has been synthesized with single sites of C-13-enrichment at various sites, and one-, two-, and three-bond C-13-H-1 spin-coupling constants ((1)J(CH), (2)J(CH), and (3)J(CH)) in these compounds have been obtained in (H2O)-H-2 by 1-D and/or 2-D NMR methods. The effects of ring configuration and conformation on these J(CH) values were assessed with the aim of identifying specific structural features that affect their magnitudes and signs. H-1 chemical shifts for the same compounds were also measured, and the data were used to derive empirical relationships between chemical shift and aldopyranosyl ring configuration. The correlations obtained on these conformationally-stable glycosides have implications for the interpretation of similar NMR parameters in biologically-important oligosaccharides and in conformationally flexible aldofuranosyl rings such as those found in DNA and RNA.