Real-Time NMR Studies of Oxyamine Ligations of Reducing Carbohydrates under Equilibrium Conditions
Real-Time NMR Studies of Oxyamine Ligations of Reducing Carbohydrates under Equilibrium Conditions
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DOI：
10.1002/chem.201603369
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发表时间：
2016-11-21
影响因子：
4.3
通讯作者：
Wittmann, Valentin
中科院分区：
文献类型：
--
作者：
Baudendistel, Oliver R.;Wieland, Daniel E.;Wittmann, Valentin
在糖的异头中心的连接反应在糖生物学领域获得了越来越多的重要性。羟胺经常用于还原性碳水化合物的标记、固定和生物缀合。在此，我们对水性条件下的这些连接反应进行了系统的研究。将一系列四种未保护的单糖（葡萄糖、N-乙酰葡糖胺、甘露糖和2-脱氧葡萄糖）和一种二糖（N，N ′-二乙酰壳二糖）与三种伯羟胺和一种仲羟胺反应。我们通过（HNMR）-H-1光谱监测起始材料和产物的浓度，并确定反应时间和平衡产率。我们的实验表明，连接反应的结果不仅取决于所用的糖和羟胺，而且强烈地依赖于反应条件。在葡萄糖的情况下，将pH从6降低到3导致稳定增加的反应速率，而产率同时降低。温度的变化不仅影响平衡产物比，而且对平衡产率也有很大影响。在伯羟胺反应的情况下，温度升高导致更高比例的无环产物。仲羟胺与葡萄糖的反应意外地导致在较高温度下较低的产率。
Ligation reactions at the anomeric center of carbohydrates have gained increasing importance in the field of glycobiology. Oxyamines are frequently used in labeling, immobilization, and bioconjugation of reducing carbohydrates. Herein, we present a systematic investigation of these ligation reactions under aqueous conditions. A series of four unprotected monosaccharides (glucose, N-acetylglucosamine, mannose, and 2-deoxyglucose) and one disaccharide (N,N'-diacetylchitobiose) was reacted with three primary and one secondary oxyamine. We monitored the concentrations of the starting materials and products by (HNMR)-H-1 spectroscopy and determined reaction times and equilibrium yields. Our experiments show that the outcome of the ligation reaction is not only dependent on the sugar and oxyamine used but also strongly on the reaction conditions. In the case of glucose, lowering the pH from 6 to 3 led to steadily increasing reaction rates, whereas the yields were decreasing at the same time. Variation of the temperature did not only influence the product ratio in equilibrium but can also have a strong impact on the equilibrium yield. In the case of reactions of a primary oxyamine, increased temperatures led to a higher proportion of acyclic products. Reaction of the secondary oxyamine with glucose unexpectedly led to lower yields at higher temperatures.