Department of Chemistry, Brandeis University, Waltham, Massachusetts 02454-9110, USA.
J Phys Chem B. 2011 May 19;115(19):5741-5. doi: 10.1021/jp1119662. Epub 2011 Apr 1.
Sugar-derived humins and melanoidins figure significantly in food chemistry, agricultural chemistry, biochemistry, and prebiotic chemistry. Despite wide interest and significant experimental attention, the amorphous and insoluble nature of the polymers has made them resistant to conventional structural characterization. Here we make use of solid-state NMR methods, including selective (13)C substitution, (1)H-dephasing, and double quantum filtration. The spectra, and their interpretation, are simplified by relying exclusively on hydronium for catalysis. The results for polymers derived from ribose, deoxyribose, and fructose indicate diverse pathways to furans, suggest a simple route to pyrroles in the presence of amines, and reveal a heterogeneous network-type polymer in which sugar molecules cross-link the heterocycles.
糖衍生的类黑精和类黑素在食品化学、农业化学、生物化学和前生物化学中起着重要作用。尽管人们对此非常感兴趣，并给予了大量的实验关注，但由于聚合物的无定形和不溶性，它们一直难以进行常规的结构表征。在这里，我们利用固态 NMR 方法，包括选择性（13）C 取代、（1）H 去相位和双量子过滤。通过仅依赖水合氢离子进行催化，简化了光谱及其解释。对于来自核糖、脱氧核糖和果糖的聚合物的结果表明了呋喃的多种途径，在存在胺的情况下，表明了吡咯的简单途径，并揭示了一种杂化的网络型聚合物，其中糖分子交联杂环。
