Laccase catalyses phytophenol furanocyclic dimerization: Substrate specificity and diastereoselective process

Abstract

Lacasse can transform phytophenol into furanocyclic dimers, including coumaran linkage dimer and 3,7-dioxabicyclo[3.3.0]octane linkage dimer. However, the substrate specificity and diastereoselective process remain unknown until now. The study therefore selected a series of monomeric phytophenol isomers or analogues as substrates to interact with laccase from Trametes versicolor (Lac TV). The products were rapidly identified by ultra-performance liquid chromatography coupled with high-resolution mass-spectrometry. On this basis, 9 dimerization reactions were established for a systematical structure–function relationship analysis. Through analysis, it can be concluded that, phytophenol furanocyclic dimerization requires a specific substrate structure, i.e., a C=C bond sitting at the -OH para-position and also conjugating with the phenolic core. The coumaran linkage dimerization presents “7,8 diastereoselectivity” character; while the 3,7-dioxabicyclo[3.3.0]octane linkage dimerization shows not only “7,8 diastereoselectivity” character but also “cis- 8H,8′H” character. The former character is attributed to the intramolecular nucleophilic addition which always prevents the Re-attack. The latter character however is caused by a substantial energy gap between normal envelop conformation and twist envelop conformation. All these findings can help to efficiently utilize Lac TV tool for phytophenol biosynthesis in chemistry fields.