Enantioselective Synthesis of Pharmaceutically Relevant Bulky Arylbutylamines Using Engineered Transaminases

ATAs engineered for having an enlarged small binding pocket were applied for the synthesis of enantiomerically pure (R)‐benzo[1,3]dioxol‐5‐yl‐butylamine, a chiral component of human leukocyte elastase inhibitor DMP 777 (L‐694,458). Kinetic resolution of the racemic amine was performed by using the L59A variant of the (S)‐selective ATA from Chromobacterium violaceum (Cv‐ATA), providing the residual (R)‐enantiomer in excellent yield and >99% ee. At moderate enzyme loading and absence of co‐solvent, high volumetric productivity of 0.22 mol L⁻¹ h⁻¹ (42.5 g L⁻¹ h⁻¹) was achieved. Complementarily, the (S)‐enantiomer was generated via kinetic resolution using the (R)‐selective ATA‐117‐Rd11 from Arthrobacter sp. with acetone as the amino acceptor. In an alternative approach, we employed ATA‐117‐Rd11 for the asymmetric amination of the prochiral ketone precursor, which at 86% conversion gave the (R)‐benzo[1,3]dioxol‐5‐yl‐butylamine with excellent >99% ee. We further evaluated the utility of Cv‐ATA L59A for the asymmetric synthesis of pharmaceutically relevant (S)‐1‐phenylbutan‐1‐amine, a chiral component of the deubiquitinase inhibitor degrasyn (WP1130). The enzyme showed good tolerance to high concentrations of isopropylamine, producing (S)‐1‐phenylbutan‐1‐amine in enantiomerically pure form (>99% ee)

Synthesis of Deoxysugars from Aliphatic α‐Ketoacids and Aldoses Catalyzed by Thermostable Transketolase Variants from Geobacillus stearothermophilus

International audienceWe described a strategy for the enzymatic synthesis of 1-deoxy and 1,2-deoxyketoses from the aliphatic α-ketoacids, pyruvate and 2-oxobutyrate, as donors and natural aldoses of variable chain length as acceptors, catalyzed by thermostable transketolase variants from Geobacillus stearothermophilus (TKgst). Analytical studies have been carried out on a panel of TKgst variants with the appropriate substrates allowing to select the best combinations and to apply it to the preparative scale synthesis of 1-deoxy and 1,2-deoxyketoses obtained with good to excellent isolated yields (61%–86%). To optimize the strategy, and as a proof of principle, the α-ketoacids pyruvate and 2-oxobutyrate were generated in situ from the corresponding d-amino acids d-alanine and d-homoalanine respectively, using a thermostable d-amino acid oxidase dAAO4536 that was selected from a screening of 55 putative DAAOs provided by Prozomix Limited. Hence, a one-pot one step procedure was performed at 50 °C by coupling dAAO4536 and the best TKgst variant H102L/L118I/H474S in the presence of d-alanine or d-homoalanine as α-ketoacids precursors and d-erythrose as acceptor substrate. The corresponding 1-deoxy and 1,2-dideoxyketoses were isolated with good yields (64% and 72% respectively, out of two steps)

Enantioselective Synthesis of Pharmaceutically Relevant Bulky Arylbutylamines Using Engineered Transaminases

ATAs engineered for having an enlarged small binding pocket were applied for the synthesis of enantiomerically pure (R)-benzo[1,3]dioxol-5-yl-butylamine, a chiral component of human leukocyte elastase inhibitor DMP 777 (L-694,458). Kinetic resolution of the racemic amine was performed by using the L59A variant of the (S)-selective ATA from Chromobacterium violaceum (Cv-ATA), providing the residual (R)-enantiomer in excellent yield and >99% ee. At moderate enzyme loading and absence of co-solvent, high volumetric productivity of 0.22 mol L-1 h(-1) (42.5 g L-1 h(-1)) was achieved. Complementarily, the (S)-enantiomer was generated via kinetic resolution using the (R)-selective ATA-117-Rd11 from Arthrobacter sp. with acetone as the amino acceptor. In an alternative approach, we employed ATA-117-Rd11 for the asymmetric amination of the prochiral ketone precursor, which at 86% conversion gave the (R)-benzo[1,3]dioxol-5-yl-butylamine with excellent >99% ee. We further evaluated the utility of Cv-ATA L59A for the asymmetric synthesis of pharmaceutically relevant (S)-1-phenylbutan-1-amine, a chiral component of the deubiquitinase inhibitor degrasyn (WP1130). The enzyme showed good tolerance to high concentrations of isopropylamine, producing (S)-1-phenylbutan-1-amine in enantiomerically pure form (>99% ee)

Regiodivergent Radical Termination for Intermolecular Biocatalytic C–C Bond Formation

Radical hydrofunctionalizations of electronically unbiased dienes are challenging to render regioselective, because the products are nearly identical in energy. Here, we report two engineered FMN-dependent “ene”-reductases (EREDs) that catalyze regiodivergent hydroalkylations of cyclic and linear dienes. While previous studies focused exclusively on the stereoselectivity of alkene hydroalkylation, this work highlights that EREDs can control the regioselectivity of hydrogen atom transfer, providing a method for selectively preparing constitutional isomers that would be challenging to prepare using traditional synthetic methods. Engineering the ERED from Gluconabacter sp. (GluER) furnished a variant that favors the γ,δ-unsaturated ketone, while an engineered variant from a commercial ERED panel favors the δ,ε-unsaturated ketone. The effect of beneficial mutations has been investigated using substrate docking studies and the mechanism probed by isotope labeling experiments. A variety of α-bromo ketones can be coupled with cyclic and linear dienes. These interesting building blocks can also be further modified to generate difficult-to-access heterocyclic compounds