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首页> 外文期刊>Chemistry: A European journal >Real-Time NMR Studies of Oxyamine Ligations of Reducing Carbohydrates under Equilibrium Conditions
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Real-Time NMR Studies of Oxyamine Ligations of Reducing Carbohydrates under Equilibrium Conditions

机译：平衡条件下还原碳水化合物的氧胺连接的实时NMR研究

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摘要

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.
机译：在碳水化合物的异头异构中心的连接反应在糖生物学领域已变得越来越重要。氧化胺经常用于还原性碳水化合物的标记，固定和生物结合。本文中，我们提出了在水性条件下这些连接反应的系统研究。使一系列的四个未保护的单糖（葡萄糖，N-乙酰氨基葡糖，甘露糖和2-脱氧葡萄糖）和一个二糖（N，N'-二乙酰基壳二糖）与三个伯氧胺和一个仲氧胺反应。我们通过（HNMR）-H-1光谱监测了起始原料和产物的浓度，并确定了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氧胺，而且还强烈取决于反应条件。在葡萄糖的情况下，将pH从6降低到3导致反应速率稳定增加，而产率同时下降。温度的变化不仅影响平衡时的产物比率，而且对平衡产率也有很大的影响。在伯氧胺反应的情况下，升高的温度导致更高比例的无环产物。仲氧胺与葡萄糖的反应出乎意料地导致在较高温度下较低的产率。

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