Biocatalytic access to nonracemic γ-oxo esters via stereoselective reduction using ene-reductases

Abstract

The asymmetric bioreduction of α,β-unsaturated γ-keto esters using ene-reductases from the Old Yellow Enzyme family proceeds with excellent stereoselectivity and high conversion levels, covering a broad range of acyclic and cyclic derivatives. Various strategies were employed to provide access to both enantiomers, which are versatile precursors of bioactive molecules. The regioselectivity of hydride addition on di-activated alkenes was elucidated by isotopic labeling experiments and showed strong preference for the keto moiety as activating/binding group as opposed to the ester. Finally, chemoenzymatic synthesis of (R)-2-(2-oxocyclohexyl)acetic acid was achieved in high ee on a preparative scale combining enzymatic reduction followed by ester hydrogenolysis. Scheme 1 γ-Oxo acids and esters employed as precursors of biologically active molecules. 1 † Electronic supplementary information (ESI) available: Synthetic procedures and NMR data. See Scheme 4 Access to (R)-2-(2-oxocyclohexyl)acetic acid [(R)-7b] via chemoenzymatic bioreduction-deprotection using NCR. Scheme 5 Elucidation of the anchor group of di-activated substrates (exemplified for 3a) in ene-reductases via incorporation of deuterium.Scheme 6 Baker's yeast catalyzed bioreduction of rac-8b for determination of absolute configuration. 14 Green Chemistry PaperThis journal is

First and Highly Stereoselective Synthesis of Both Enantiomers of Octahydroindole‐2‐phosphonic Acid (OicP)

“…The residue was purified by flash column chromatography (CH 2 Cl 2 /MeOH, 95:5) to give (±)‐ 5 (1.6 g, 96 %) as a yellow oil. The spectroscopic data for (±)‐ 5 are identical to those reported in the literature …”

Stereoselective Synthesis of Functionalized Bicyclic Scaffolds by Passerini 3‐Center‐2‐Component Reactions of Cyclic Ketoacids

“…Finally, we attempted to control not only the diastereoselectivity, but also the absolute stereochemistry during our intramolecular Passerini reaction . Thus, asymmetric bioreduction of unsaturated keto ester 5 with the nicotinamide‐dependent ene‐reductase NCR from Zymomonas mobilis and subsequent hydrogenolysis delivered ( R )‐ 1a . This can then react with isocyanides to give enantioenriched Passerini products, as exemplified for 3a (Scheme ).…”

One-Pot Multi-Enzymatic Synthesis of the Four Stereoisomers of 4-Methylheptan-3-ol

“…Ene-reductases (OYE1-3, OYE1-W116V, OYE2.6, YqjM, and LeOPR1) and glucose dehydrogenase (GDH) were overproduced in E. coli BL21(DE3) strains harbouring a specific plasmid prepared as previously reported: pET30a-OYE1 from the original plasmid provided by Neil C. Bruce [ 27 ], pET30a-OYE2 and pET30a-OYE3 from S. cerevisiae BY4741 and pKTS-GDH from B. megaterium DSM509 [ 28 ]; pDJBx-OYE2.6, pDJB5-OYE1-W116V, and pDJBx-LeOPR1 from the original plasmids provided by Prof. Jon D. Stewart. For YqjM, the original plasmid provided by Prof. M. Hall was used directly as provided [ 29 ]. The enzymes were produced and purified as described in Section 4.2 .…”