Enzymatic epoxidation of β-caryophyllene using free or immobilized lipases or mycelia from the Amazon region

Abstract

• The chemo-enzymatic epoxidation of β-caryophyllene was studied. • The reactions were carried out under mild conditions. • Commercial and native lipases were used to produce the peroxy acids in situ . • The organic solvent was one of the most important parameters, and it is possible to obtain a single product. The chemo-enzymatic epoxidation of the terpene β-caryophyllene is reported herein. This compound can form two products, the mono-epoxide 2 and the di-epoxide 3 . Different experimental conditions, varying the source of the lipases (including mycelia from the Amazon region), the oxidizing agents (H 2 O 2 aq. (AHP) or urea-hydrogen peroxide (UHP)) and the substituted acyl donors on the alkyl chain (bromide and alkyl), along with the influence of organic medium, were evaluated. Depending on the experimental conditions the formation of a single product could be obtained. CAL-B was the most efficient catalyst (conv. >99%). When using the commercial lipases product 2 was obtained in conversions of 16–27%, and using the native lipases 2 was obtained in conversions of 20–23%. With the use of mycelia UEA_06 and UEA_53 the conversions were 16 and 21%, respectively. When the 2-bromo alkylated and 2-ethylhexanoic acids were used as acyl donors only the mono-epoxide 2 was obtained in conversions of 14–54% (24 h). AHP was found to be a better oxidizing agent than UHP, a shorter time and lower amount being required to obtain 2 or 3 as the sole product in good conversions (60 up to >99%). The organic solvents were also selective. When using n -hexane the preferred formation of 2 was observed with >99% conversion, and when ethyl acetate or toluene were used the conversion to 3 was also >99% (in 8 and 24 h, respectively).