Engineering of Saccharomyces pastorianus old yellow enzyme 1 for the synthesis of pharmacologically active (S)-profen derivatives

Strategic enzymatic enantioselective desymmetrization of prochiral cyclohexa-2,5-dienones

Asymmetric desymmetrization through the selective reduction of one double bond of prochiral 2,5-cyclohexadienones is highly challenging. A novel method has been developed for synthesizing chiral cyclohexenones by employing an ene-reductase (Bacillus subtilis YqjM) enzyme that belongs to the OYE family. Our strategy demonstrates high substrate scope and enantioselectivity towards substrates containing all-carbon as well as heteroatom (O, N)-containing quaternary centers. The mechanistic studies (kH/D = ∼1.8) indicate that hydride transfer is probably the rate-limiting step. Mutation of several active site residues did not affect the stereochemical outcomes. This work provides a convenient way of synthesizing various enantioselective γ,γ-disubstituted cyclohexanones using enzymes.

Highly Enantioselective Synthesis of Pharmaceuticals at Chiral-Encoded Metal Surfaces

Enantioselective catalysis is of crucial importance in modern chemistry and pharmaceutical science. Although various concepts have been used for the development of enantioselective catalysts to obtain highly pure chiral compounds, most of them are based on homogeneous catalytic systems. Recently, we successfully developed nanostructured metal layers imprinted with chiral information, which were applied as electrocatalysts for the enantioselective synthesis of chiral model compounds. However, so far such materials have not been employed as heterogeneous catalysts for the enantioselective synthesis of real pharmaceutical products. In this contribution, we report the asymmetric synthesis of chiral pharmaceuticals (CPs) with chiral imprinted Pt-Ir surfaces as a simple hydrogenation catalyst. By fine-tuning the experimental parameters, a very high enantioselectivity (up to 95 % enantiomeric excess) with good catalyst stability can be achieved. The designed materials were also successfully used as catalytically active stationary phases for the continuous asymmetric flow synthesis of pharmaceutical compounds. This illustrates the possibility of producing real chiral pharmaceuticals at such nanostructured metal surfaces for the first time.

Design and engineering of whole-cell biocatalyst for efficient synthesis of (R)-citronellal

Bioproduction of optical pure (R)‐citronellal from (E/Z)‐citral at high substrate loading remains challenging. Low catalytic efficiency of (R)‐stereoselective ene reductases towards crude citral mixture is one of the major bottlenecks. Herein, a structure‐based engineering strategy was adopted to enhance the catalytic efficiency and stereoselectivity of an ene reductase (OYE2p) from Saccharomyces cerevisiae YJM1341 towards (E/Z)‐citral. On basis of homologous modelling, molecular docking analysis and alanine scanning at the binding pocket of OYE2p, a mutant Y84A was obtained with simultaneous increase in catalytic efficiency and stereoselectivity. Furthermore, site‐saturation mutagenesis of Y84 yielded seven mutants with improved activity and stereoselectivity in the (E/Z)‐citral reduction. Among them, the variant Y84V exhibited an 18.3% and 71.3% rise in catalytic efficiency (k_cat/K_m) for (Z)‐citral and (E)‐citral respectively. Meanwhile, the stereoselectivity of Y84V was improved from 89.2% to 98.0% in the reduction in (E/Z)‐citral. The docking analysis and molecular dynamics simulation of OYE2p and its variants revealed that the substitution Y84V enabled (E)‐citral and (Z)‐citral to bind with a smaller distance to the key hydrogen donors at a modified (R)‐selective binding mode. The variant Y84V was then co‐expressed with glucose dehydrogenase from Bacillus megaterium in E. coli D4, in which competing prim‐alcohol dehydrogenase genes were deleted to prevent the undesired reduction in the aldehyde moiety of citral and citronellal. Employing this biocatalyst, 106 g l⁻¹ (E/Z)‐citral was completely converted into (R)‐citronellal with 95.4% ee value and a high space‐time yield of 121.6 g l⁻¹ day⁻¹. The work highlights the synthetic potential of Y84V, which enabled the highest productivity of (R)‐citronellal from (E/Z)‐citral in high enantiopurity so far.