A novel resolution of a pharmaceutically important bridged bicyclic ketone intermediate via selective enzymatic reduction with a commercially available ketoreductase

Ketoreductase Catalyzed (Dynamic) Kinetic Resolution for Biomanufacturing of Chiral Chemicals

Biocatalyzed asymmetric reduction of ketones is an environmentally friendly approach and one of the most cost-effective routes for producing chiral alcohols. In comparison with the well-studied reduction of prochiral ketones to generate chiral alcohols with one chiral center, resolution of racemates by ketoreductases (KREDs) to produce chiral compounds with at least two chiral centers is also an important strategy in asymmetric synthesis. The development of protein engineering and the combination with chemo-catalysts further enhanced the application of KREDs in the efficient production of chiral alcohols with high stereoselectivity. This review discusses the advances in the research area of KRED catalyzed asymmetric synthesis for biomanufacturing of chiral chemicals with at least two chiral centers through the kinetic resolution (KR) approach and the dynamic kinetic resolution (DKR) approach.

Biomimetic kinetic resolution: highly enantio- and diastereoselective transfer hydrogenation of aglain ketones to access flavagline natural products

We have previously reported asymmetric syntheses and absolute configuration assignments of the aglains (+)-ponapensin and (+)-elliptifoline and proposed a biosynthetic kinetic resolution process to produce enantiomeric rocaglamides and aglains. Herein, we report a biomimetic approach for the synthesis of enantiomerically enriched aglains and rocaglamides via kinetic resolution of a bridged ketone utilizing enantioselective transfer hydrogenation. The methodology has been employed to synthesize and confirm the absolute stereochemistries of the pyrimidone rocaglamides (+)-aglaiastatin and (-)-aglaroxin C. Additionally, the enantiomers and racemate of each metabolite were assayed for inhibition of the heat-shock response, cytotoxicity, and translation inhibition.

Enantioselective photocycloaddition of 3-hydroxyflavones: total syntheses and absolute configuration assignments of (+)-ponapensin and (+)-elliptifoline

We have previously reported development of biomimetic, asymmetric [3 + 2] photocycloadditions between 3-hydroxyflavones and cinnamate dipolarophiles to access (-)-rocaglamide and related natural products. Herein, we describe enantioselective syntheses of aglain cycloadducts leading to the first total syntheses and absolute configuration assignments of the aglain natural products (+)-ponapensin and (+)-elliptifoline.

ESR, electrochemical and cyclodextrin-inclusion studies of triazolopyridyl pyridyl ketones and dipyridyl ketones derivatives

The electron spin resonance (ESR) spectra of free radicals obtained by electrolytic reduction of triazolopyridyl pyridyl ketones and dipyridyl ketones derivatives were measured in dimethylsulfoxide (DMSO). The hyperfine patterns indicate that the spin density delocalization is dependent of the rings presented in the molecule. The electrochemistry of these compounds was characterized using cyclic voltammetry, in DMSO as solvent. When one carbonyl is present in the molecule one step in the reduction mechanism was observed while two carbonyl are present two steps were detected. The first wave was assigned to the generation of the correspondent free radical species, and the second wave was assigned to the dianion derivatives. The phase-solubility measurements indicated an interaction between molecules selected and cyclodextrins in water. These inclusion complexes are 1:1 with betaCD, and HP-betaCD. The values of Ks showed a different kind of complexes depending on which rings are included. AM1 and DFT calculations were performed to obtain the optimized geometries, theoretical hyperfine constants, and spin distributions, respectively. The theoretical results are in complete agreement with the experimental ones.

Vegetables as chemical reagents

Biocatalysis is an important adjunct to the chemical armamentarium that organic chemists may bring to bear for the synthesis of important intermediates and finished pharmaceutical and other commercial products. For most of the world however, such catalytic reagents are not an option due to their high cost and import limitations. Recent studies indicate that the use of locally available vegetables may offer an alternative opportunity for countries to investigate their local resources for the effective conduct of key synthetic transformations with significant economic and ecological implications. This review offers a brief overview of the field of microbial and plant biocatalysts, discusses the studies thus far on the use of intact plant materials for conducting synthetic chemical reactions, and considers some opportunities for future development.

Enzyme-Catalyzed Enantioselective Diaryl Ketone Reductions

The synthesis of diarylmethanols via the reduction of a range of substituted benzophenone and benzoylpyridine derivatives with ketoreductase enzymes (KREDs) has afforded chiral products with high yield (>90%) and ee (up to >99%). Ortho, meta, and para substitutions with a variety of electron-donating, electron-withdrawing, and halogen groups were examined. Substitution at the ortho position and/or highly electronically dissymmetric molecules were not required for good selectivity, as is the case with conventional chemical catalyst reductions. [reaction: see text].