Deuterium nuclear spin-lattice relaxation times and quadrupolar coupling constants in isotopically labeled saccharides.

Abstract 13 C and 2 H spin–lattice relaxation times have been determined by inversion recovery in a range of site-specific 13 C- and 2 H-labeled saccharides under identical solution conditions, and the data were used to calculate deuterium nuclear quadrupolar coupling constants ( 2 H NQCC) at specific sites within cyclic and acyclic forms in solution. 13 C T 1 values ranged from ∼0.6 to 8.2 s, and 2 H T 1 values ranged from ∼79 to 450 ms, depending on molecular structure (0.4 M sugar in 5 mM EDTA (disodium salt) in 2 H 2 O-depleted H 2 O, pH 4.8, 30°C). In addition to providing new information on 13 C and 2 H relaxation behavior of saccharides in solution, the resulting 2 H1 NQCC values reveal a dependency on anomeric configuration within aldopyranose rings, whereas 2 H NQCC values at other ring sites appear less sensitive to configuration at C1. In contrast, 2 H NQCC values at both anomeric and nonanomeric sites within aldofuranose rings appear to be influenced by anomeric configuration. These experimental observations were confirmed by density functional theory (DFT) calculations of 2 H NQCC values in model aldopyranosyl and aldofuranosyl rings.