Abstract
A lignin model oligomer with only β-O-4 linkages and a selectively deuterium-labelled methoxy group at the phenolic terminal units was synthesised to clarify the behaviour of the phenolic end of oligolignols. First, t-butoxycarbonylmethyl vanillin was synthesised and oligomerised by nucleophilic addition, a known method. The terminal of the oligomers was then subjected to nucleophilic addition to [3-OCD3]benzyl vanillin to achieve selective labelling of the terminal units. A deuterium-labelled lignin model oligomer (D-LM) was obtained through debenzylation and subsequent reduction. The results of thioacidolysis after methylation revealed that the degree of polymerisation was about five, and the deuterium-labelled phenylpropane unit was located only at the phenolic terminal moiety.
Funding source: Japan Society for the Promotion of Science
Award Identifier / Grant number: 23H02274
Funding source: Tokyo University of Agriculture
Award Identifier / Grant number: Unassigned
Acknowledgments
The NMR measurements were performed at Tokyo University of Agriculture and Technology for Smart Core Facility Promotion Organization.
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Research ethics: Not applicable.
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Author contributions: YM, TN, KT, DA, and KF conceived the research. TN, KT, and YM synthesized chemical compounds. YM, TN, KT, and DA conducted NMR measurements. TN, YM, and DA wrote the manuscript. All authors read and contributed to the manuscript.
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Competing interests: The authors state no competing interests.
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Research funding: This work was supported by JSPS KAKENHI grant number 23H02274.
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Data availability: The raw data can be obtained on request from the corresponding author.
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Supplementary Material
This article contains supplementary material (https://doi.org/10.1515/hf-2023-0095).
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