Sensitive NMR method for detecting carbohydrate influx into competing chemocatalytic pathways

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 allow...

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Bibliographic Details
Published in:Analyst (London) 2020-07, Vol.145 (13), p.4427-4431
Main Authors: Elliot, Samuel G, Jessen, Bo M, Taarning, Esben, Madsen, Robert, Meier, Sebastian
Format: Article
Language:English
Subjects:
Biomass
Carbohydrates
Carbon 13
NMR spectroscopy
Reaction products
Substrates
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Summary: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 NaBH 4 to install hydrogens at each carbon site in the product. In this manner, the detection of 13 C and 12 C sites becomes possible in multiplets of the sensitive 2D 1 H- 1 H 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. Mechanistic pathway studies in sustainable chemistry can be accelerated and have increased information content through the indirect detection of isotope-tracking experiments upon reduction of quaternary carbon sites.
ISSN:0003-2654
1364-5528
DOI:10.1039/d0an00555j