Natsuko Cyr

13C-1H inter-residue, coupling in disaccharides, and the orientations of glycosidic bonds☆

Abstract In examining orientations of glycosidic linkages, measurements of three-bond coupling between 13 C-1 and 1 H-4′, or 13 C-4′ and 1 H-1, have been made from natural abundance, 1 H-coupled, 13 C-n.m r. spectra of maltose, cyclohexaamylose, and related compounds. Maltose and cyclohexaamylose in water exhibit inter-residue 13 COC 1 H couplings of close to 3 Hz. In terms of torsional angles, φ and ψ, these findings suggest that, in aqueous solution, the molecules favor conformations that are appreciably more staggered than those known to exist in the solid state. Analogous measurements on O -acetyl derivatives suggest that φ is smaller, and ψ larger, than in maltose. Data are also presented for sucrose, maltosan, and α,α-trehalose.