Biocatalytic Asymmetric Oxidations with Monooxygenases

Both chemical and enzymatic synthetic methods for the asymmetric oxidation of the carbon-carbon double bond have been developed [46], but the area of carbon-carbon double bond oxidations has been shaped by the breakthrough discovery of asymmetric epoxidation of allylic alcohols with the Katsuki-Sharpless method [47]. Catalytic asymmetric synthesis of epoxides from alkenes by Jacobsen 

Heme-dependent monooxygenases contain ferric protoporphyrin IX, the heme, as the cofactor and protect us from the xenobiotics, toxins, food, and chemicals we take up. As these proteins exhibit a very strong absorption band maximum at 

Non-heme iron-containing monooxygenases are able to catalyze the oxidation of hydrocarbons to the corresponding hydrocarbon alcohols and have been found in methanotrophic bacteria [58]. 

Dopamine hydroxylase belongs to the copper-dependent monooxygenases and is important in the control of the neurotransmitter concentrations of dopamine and norepinephrine [59]. 

The important metaboUsm of the neurotransmitters norepinephrine, epinephrine, dopa, and serotonin involves pterin-dependent monooxygenases. The direct biocatalytic hydroxylation of the aromatic amino acids phenylalanine, tyrosine, and tryptophane requires tetrahydrobiopterin and Fe as the cofactors [60]. The cleavage of unsaturated glyceryl ethers by glyceryl ether monooxygenase also requires tetrahydrobioterin as the cofactor [61]. 

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Based on the above observations, the employment of chiral metal catalysts for the asymmetric BV oxidation is still underdeveloped for practical appUcations on the scale of natural products and drugs synthesis. Only biocatalytic BV oxidations performed with isolated enzymes or whole cells containing cyclohexanone monooxygenases (CHMOs) or BV monooxygenases (BVMOs) shows practical conversions as weU as enantioselectivity above 95% ee with cyclohexanones as substrates. 

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