Studies on the Dehydrogenative Polymerizations of Monolignol β-glycosides. Part 3: Horseradish Peroxidase–Catalyzed Polymerizations of Triandrin and Isosyringin

Abstract

Horseradish peroxidase–catalyzed dehydrogenative polymerizations of the p-hydroxyphenyl monolignol glucoside (triandrin (1P)) and the syringyl monolignol glucoside (isosyringin (1S)) resulted in the formation of water-soluble lignin-like polymers (DHPs). The polymerization of 1P gave highly polymerized DHPs in high yields as did previously reported polymerization of the guaiacyl monolignol glucoside (isoconiferin (1G)). It was shown that the hydrophilic D-glucose units of 1G and 1P contribute to a marked increase in the molecular weights of the resulting DHPs. On the other hand, the homogeneous phase polymerization of 1S, similar to the polymerization of sinapyl alcohol, gave DHPs with extremely low molecular masses in poor yields. Structural characterization indicated that the DHPs from 1P and 1S were lignin-like polymers containing glucosidic units on their sidechains. It was also confirmed that D-glucosyl units introduced onto the γ-position of monolignols do not significantly affect the electrochemical oxidizability and the kinetics of the HRP-catalyzed initial monomer consumption.

Keywords:

• Cyclic voltammetry
• dehydrogenative polymerization
• dehydrogenation polymer (DHP)
• horseradish peroxidase (HRP)
• lignin
• monolignol β
• -D-glucoside

This research was supported by a Grant-in-Aid for Scientific Research (No. 18580162), from the Ministry of Education, Science, Sports and Culture, Japan.

Notes

^a Per 1 mmol monomer

^b Calculated based on monomer's molecular weight

^c Determined after acetylation

^a In H₂O, c = 0.1.

^b The proportions of lignin structures were calculated based on monomer structures.