Epoxide hydrolase synthetic chemistry

Several reports regarding the directed evolution of enantioselective epoxide hydrolases (EHs) have appeared [23,57-59]. These enzymes constitute important catalysts in synthetic organic chemistry [4,60]. The first two reported studies concern the Aspergillus niger epoxide hydrolase (ANEH) [57,58]. Initial attempts were made to enhance the enantioselectivity of the AN E H -catalyzed hydrolytic kinetic resolution of glycidyl phenyl ether (rac-19). The WT leads to an Evalue of only 4.6 in favor of (S)-20 (see Scheme 2.4) [58]. 

Wong, C.-H., Whitesides, G. M. Chapter 2 Use of Hydrolytic Enzymes Amidases, Proteases, Esterases, Lipases, Nitrilases, Phosphatases, Epoxide Hydrolases. In Enzymes in Synthetic Organic Chemistry, Elsevier New York, 1994, p. 41. 

Overall, epoxide hydrolases are very important enzymes for the as5mimetric synthesis of optically pure epoxides and 1,2-diols. The biphasic application of EHs and the development of continuous processes have made them industrially attractive In spite of that, thdr application in synthetic chemistry is still limited due to low regioselectivity, chemical instability, low solubility of epoxides in water and awiilable alternative chemical routes. Nevertheless, it is important to exploit and investigate new epoxide hydrolases for synthetic routes to chiral epoxides and diols. 

Other, more complex applications of hydrolases, such as those involving the formation and/or cleavage of phosphate esters, epoxides, nitriles, and organo-halides, are described elsewhere in this book. In contrast to the group of proteases, esterases and lipases, they have had less impact on organic chemistry, although their synthetic potential should not be underestimated. 

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