Enzymatic Epoxidation of Long-Chain Terminal Alkenes by Fungal Peroxygenases

Abstract

Terminal alkenes are among the most attractive starting materials for the synthesis of epoxides, which are essential and versatile intermediate building blocks for the pharmaceutical, flavoring, and polymer industries. Previous research on alkene epoxidation has focused on the use of several oxidizing agents and/or different enzymes, including cytochrome P450 monooxygenases, as well as microbial whole-cell catalysts that have several drawbacks. Alternatively, we explored the ability of unspecific peroxygenases (UPOs) to selectively epoxidize terminal alkenes. UPOs are attractive biocatalysts because they are robust extracellular enzymes and only require H2O2 as cosubstrate. Here, we show how several UPOs, such as those from Cyclocybe (Agrocybe) aegerita (AaeUPO), Marasmius rotula (MroUPO), Coprinopsis cinerea (rCciUPO), Humicola insolens (rHinUPO), and Daldinia caldariorum (rDcaUPO), are able to catalyze the epoxidation of long-chain terminal alkenes (from C12:1 to C20:1) after an initial optimization of several reaction parameters (cosolvent, cosubstrate, and pH). In addition to terminal epoxides, alkenols and other hydroxylated derivatives of the alkenes were formed. Although all UPOs were able to convert and epoxidize the alkenes, notable differences were observed between them, with rCciUPO being responsible for the highest substrate turnover and MroUPO being the most selective with respect to terminal epoxidation. The potential of peroxygenases for epoxidizing long-chain terminal alkenes represents an interesting and green alternative to the existing synthesis technologies.

Vesicle-based cell-free synthesis of short and long unspecific peroxygenases

“…The efficiency of the conversion of cyclophosphamide was dependent on the UPO that was used (Steinbrecht et al, 2020). Substantial differences in the catalytic activity of different UPOs were also reported for substrates like long chain terminal alkenes (Babot et al, 2022) and isophorone derivatives (Aranda et al, 2019). This underlines the need for a comprehensive UPO toolbox to take advantage of the full catalytic potential of UPOs.…”

Asymmetric Bio‐epoxidation of Unactivated Alkenes

“…As a class of valuable catalysts, HTPs-type enzymes have great potential in catalyzing the asymmetric epoxidation of various alkenes. [22,59,100] However, the low level of heterologous expression in other host cells limits its wider application, so the adoption of various strategies to increase the level of heterologous expression will promote the further development of these enzymes in biocatalytic oxygen functionalization reactions.…”

Catalyzing the Development of Self-Efficacy and Science Identity: A Green Organic Chemistry CURE

“…The reaction chosen for optimization was a green epoxidation reaction that worked well for reactive alkene substrates but was slow for deactivated alkenes, like trans -stilbene . An epoxidation reaction was chosen, as epoxides are universally studied in a wide array of chemistry applications, ranging from polymer and material chemistry − to biochemical reactions catalyzed by cytochrome P450s. − Epoxides also have applications as useful synthetic intermediates for preparing diverse carbon skeletons, , especially given their straightforward preparation from alkenes. However, alkene epoxidation has historically used conditions that are environmentally unfriendly or dangerous. , Efforts in the literature have addressed these environmental concerns, but green epoxidation procedures have been limited to more “activated” alkene substrates, such as alkenes that have few electron-withdrawing groups (EWGs) (e.g., styrene), have electron-donating groups (EDGs) (e.g., cyclohexene), and/or involve the use of metal catalysts. , There are fewer literature examples of using deactivated alkene derivatives, such as alkenes with multiple EWGs ( trans -stilbene) using metal-free green procedures. , …”