Deracemization and Stereoinversion of Alcohols Using Two Mutants of Secondary Alcohol Dehydrogenase from Thermoanaerobacter pseudoethanolicus

Abstract

We developed a one-pot two-step deracemization approach for alcohols using two mutants of Thermoanaerobacter pseudoethanolicus secondary alcohol dehydrogenase ( Te SADH). This approach relies on consecutive non-stereospecific oxidation of alcohols and stereoselective reduction of their prochiral ketones using two mutants of Te SADH with poor and good stereoselectivities, respectively. More specifically, W110G Te SADH enables a non-stereospecific oxidation of alcohol racemates to their corresponding prochiral ketones, followed by W110V Te SADH-catalyzed stereoselective reduction of the resultant ketone intermediates to enantiopure ( S )-configured alcohols in up to >99% enantiomeric excess. A heat treatment after the oxidation step was required to avoid the interference of the marginally stereoselective W110G Te SADH in the reduction step; this heat treatment was eliminated by using sol-gel encapsulated W110G Te SADH in the oxidation step. Moreover, this bi-enzymatic approach was implemented in the stereoinversion of ( R )-configured alcohols, and ( S )-configured alcohols with up to >99% enantiomeric excess were obtained by this Mitsunobu-like stereoinversion reaction.