Asymmetric Epoxidation of Aliphatic Alkenes

3 APPLICATION OF BIOEPOXIDATION IN ORGANIC SYNTHESIS 13.3.1 Asymmetric Epoxidation of Aliphatic Alkenes 

For ffie past several decades, several chemocatalysts and biocatalysts have been used for ffie epoxidation of nonfunctionalized aliphatic alkenes. The Katsuki-Jacobsen epoxidation, which is catalyzed by chiral Mn(III)-salen with NaOCl/PhIO as an oxidant, achieves good yields and high stereoselectivities (84-94%ee) for ffie epoxidation of ds-alkenes [21]. The Shi epoxidation, which is catalyzed by ffie fructose-derived ketone and oxone, has been successfully used in ffie epoxidation of frans-alkenes, yielding ffie corresponding oxides with 93-98% ee [74]. However, for nonfunctionalized terminal aliphatic alkenes, chemocatalysts typically display low stereoselectivity [7]. 

On ffie other hand, some oxidoreductases accept those substrates well enough to serve as complementary catalysts. Among them, alkene monooxygenases and CPO 

Reactions Catalyzed with Nonheme Iron-Dependent Monooxygenases 

Microorganisms that use gaseous olefins as a carbon source are widely exist in nature, and they typically produce nonheme iron-dependent alkene/alkane monooxygenases. Although in a lot of cases, the identification of the key enzyme hasn t been attempted many of those alkene-utilizing bacteria have been used in the asymmetric epoxidation of aliphatic alkenes with high stereoselectivities [26]. 

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Recently, the SMO from Rhodococcus sp. ST-5 and ST-10 have been applied to catalyze the epoxidation of 1-hexene and 1-octene to the corresponding (S)-epoxides with up to 99% ee [58]. For 1-hexene, the activity was comparable to that acquired with the native substrate styrene [58], but the initial conversion rate was four times lower than styrene [92]. The excellent (S)-stereoselectivity is a complementary to the (R)-selectivity of majority of the enzymes involved in the asymmetric epoxidation of aliphatic alkenes. 

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