Reaction pathways are often tracked with stable isotopes in order to determine the provenance of products in the pathway and to deduce mechanistic information. NMR spectroscopy can provide direct insight into the specific labelling position of the stable isotope. We suggest a simple assay that allows rapid quantitative measurements of isotope distributions in biomass-derived products using commercially available carbohydrate substrates and routine instrumentation. In the assay, biomass-derived products in post reaction material are quantitatively reduced with NaBH₄ to install hydrogens at each carbon site in the product. In this manner, the detection of ¹³C and ¹²C sites becomes possible in multiplets of the sensitive 2D ¹H–¹H TOCSY experiment. The approach detects the usage of competing upstream reactions from isotope patterns in chemically identical reaction products. Changing influx into Sn-Beta-catalysed carbohydrate conversion reactions in the absence and in the presence of K⁺ was quantitatively assessed, showing how the presence of K⁺ alters the intial reactions towards methyl lactate.

中文翻译：

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用于检测碳水化合物流入竞争性化学催化途径的灵敏NMR方法。

通常用稳定的同位素追踪反应途径，以确定途径中产物的来源并推论出机理信息。NMR光谱可以直接了解稳定同位素的特定标记位置。我们建议一种简单的测定方法，该方法允许使用可商购的碳水化合物底物和常规仪器对生物质衍生产品中的同位素分布进行快速定量测量。在该测定中，用NaBH ₄定量还原反应后材料中的生物质衍生产品，以在产品的每个碳位处安装氢。通过这种方式，可以在敏感的2D ¹ H–的多重峰中检测¹³ C和¹² C的位点¹ H TOCSY实验。该方法从化学上相同的反应产物中的同位素模式检测竞争性上游反应的使用。定量评估在不存在和存在K ⁺的情况下流入Sn-Beta催化的碳水化合物转化反应的变化，显示K ⁺的存在如何改变对乳酸甲酯的初始反应。