Probing Segmental Mobility in the Cyanogenic Glycoside Amygdalin by ~(13)C Solid-State NMR

摘要

Local motions in the cyanogenic glycoside amygdalin have been charactierzed by variable-temperature ~(13)C solid-state NMR spectroscopy. Carbon-13 chemical shift tensors and ~1H-~(13)C dipolar couplings were measured by advanced magic-angle spinning NMR techniques over the temperature range 0-90 ℃. The main conclusions from our study are that the phenyl ring exhibits thermally activated dynamics about the para axis, whereas the glucopyranosyl residues remain immobile upon heating. It was also found that sample heating is accompanied by loss of water. The experimental results were complemented by quantum chemical calculations of the ~(13)C chemical shift tensors, which were utilized in the analysis of the experimental NMR parameters.