Crown Ethers as Regulators of Enzymatic Reactions: Enhanced Reaction Rate and Enantioselectivity in Lipase-Catalyzed Hydrolysis of 2-Cyano-1-methylethyl Acetate

Abstract

Both reaction rate and enantioselectivity in lipase-catalyzed hydrolysis of 2-cyano-1-methylethyl acetate were significantly changed by addition of some crown ethers. Although various crown ethers accelerated the reaction rate, the enantioselectivity greatly depended on the nature of each one. Among 27 crown ethers and 5 polyethers tested, benzo-crown, armed azacrown, and thiacrown ethers offered high enantioselectivity of the lipase-catalyzed hydrolysis. Hydrophobicity and chirality of the crown ether did not affect the hydrolysis behavior, but its concentration greatly influenced enantioselectivity. Two hundred fifty or more times the crown ether, molarity based on the enzyme, was required to attain satisfactorily high reaction rate and enantioselectivity.