Laccase-based biocatalytic reactions have been tested with and without mediators and optimized in the oxidation of allylbenzene derivatives, such as methyl eugenol taken as a model substrate. The reaction primarily consisted in the hydroxylation of the propenyl side chain, either upon isomerization of the double bond or not. Two pathways were then observed; oxidation of both allylic alcohol intermediates could either lead to the corresponding α,β-unsaturated carbonyl compound, or the corresponding benzaldehyde derivative by oxidative cleavage. Such a process constitutes a green equivalent of ozonolysis or other dangerous or waste-generating oxidation reactions. The conversion rate was sensitive to the substitution patterns of the benzenic ring and subsequent electronic effects.

Citronellol is a monoterpene alcohol biosynthesized by various plant species belonging to different families of Angiosperm. Bioinspired by the metabolism of Rosa sp. able to produce (-)-cis-rose oxide from citronellol, we have studied and optimized a laccase-catalyzed oxidation of (±)-, (R), and (S)-citronellol into rose oxides diastereomers in the presence of mediators. The reaction was found to be diastereomerically cis-selective but completely nonenantioselective. The laccase-mediator system was then applied on citronellol-containing essential oils such as lemongrass (Cymbopogon citratus) and geranium (Pelargonium graveolens) essential oils in order to modify their composition beyond the plant metabolism and increase their rose oxides content, thereby tuning their olfactory properties.