Plant-mediated biotransformations of S(+)- and R(-)-carvones

Abstract

The enzymatic system of vegetables is well known as an efficient biocatalyst in the stereoselective reduction of ketones. Therefore, we decided to use the comminuted material of several plants including five vegetables (Apium graveolens L., Beta vulgaris L., Daucus carota L., Petroselinum crispum L., and Solanum tuberosum L.) and three fruits (Malus pumila L. "Golden" and "Kortland" as well as Pyrus communis L. "Konferencja") to obtain enantiomerically pure carveol, which is commercially unavailable. Unexpectedly, all of the used biocatalysts not only reduced the carbonyl group of (4R)-(-)-carvone and (4S)-(+)-carvone, but also reduced the double bond in the cyclohexene ring. The results revealed that (4R)-(-)-carvone was transformed into (1R, 4R)- and (1S, 4R)-dihydrocarvones, and (1R,2R,4R)-dihydrocarveol. Although the enzymatic system of the potato transformed the substrate almost completely, the %de was not the highest. Potato yielded 92%; however, when carrot was used as the biocatalyst, it was possible to obtain 17% of (1R, 4R)-(+)-dihydrocarvone with 100% diastereomeric excess. In turn, the (4S)-(+)-carvone was transformed, using the biocatalysts, into (1R, 4S)- and (1S, 4S)-dihydrocarvones and dihydrocarveols. Complete substrate conversion was observed in biotransformation when potato was used. In the experiments using apple, (1R, 4S)-dihydrocarvone with 100% diastereomeric excess was obtained. Using NMR spectroscopy, we confirmed both diastereoisomers of 4(R)-1,2-dihydrocarveols, which were unseparated in the GC condition. Finally, we proved the high usefulness of vegetables for the biotransformation of both enantiomers of carvone as well as dihydrocarvone.