Enzymatic asymmetric production of substituted 2-tetralols

Optically active alcohols have been produced by several methods including kinetic resolution and deracemization of racemic alcohols or by asymmetric reduction of prochiral ketones. Asymmetric reduction of prochiral ketones using enzymes represents an attractive approach for obtaining optically active alcohols, and thus a potential substitute to asymmetric reduction using metal complexes containing chiral ligands. Herein, we propose the use of Thermoanaerobacter ethanolicus secondary alcohol dehydrogenase (TeSADH) mutants in the asymmetric reduction of phenyl-ring-substituted 2-tetralones. We will use W110A and W110G mutants of TeSADH as biocatalysts in this study. These mutants follow Prelog rule in which the pro-R hydride of the coenzyme nicotinamide-adenine dinucleotide phosphate (NADPH) is delivered from the re face of a prochiral ketone, and thus are expected to produce (S)-configured alcohols in the asymmetric reduction of prochiral ketones. We will also use W110A/I86A TeSADH as a catalyst in this study. We will conducts asymmetric reduction of substituted 2-tetralones such as 5-methoxy-2-tetralone, 7-methoxy-2-tetralone, 8-methoxy-2-tetralone, and 6-chloro-2-tetralone using the mentioned mutants of TeSADH. 2-Tetraloles are important building blocks in the anti-arrhythmical MK-0499 and the antidepressant sertraline. The produced optically active alcohols will be characterized by 1H and 13C nuclear magnetic resonance, gas chromatography-mass spectrometry and infrared. Their enantiomeric excess will be determined by a gas chromatogram equipped with a chiral column. Their configurations will be determined by measuring their optical rotation and comparing the obtained values with those reported; and for those with no reported optical rotation value, such as 6-chloro-2-tetralol, we will try to crystallize the produced alcohol by coordinating the produced alcohol with a metal to produce a complex. We will also study the kinetics of TeSADH-catalyzed asymmetric reduction reactions of substituted 2-tetralones and calculate the kinetic parameters, kcat and KM.