Chemoenzymatic one-pot reaction from carboxylic acid to nitrile oxime.

We report a new chemoenzymatic cascade starting with aldehyde synthesis by carboxylic acid reductase (CAR) followed by chemical oxime formation. The final step to the nitrile is catalyzed by aldoxime dehydratase (Oxd). Full conversions of phenylacetic acid and hexanoic acid were achieved in a two-phase mode.

Kinetic Analysis and Probing with Substrate Analogues of the Reaction Pathway of the Nitrile Reductase QueF from Escherichia coli.

The enzyme QueF catalyzes a four-electron reduction of a nitrile group into an amine, the only reaction of this kind known in biology. In nature, QueF converts 7-cyano-7-deazaguanine (preQ) into 7-aminomethyl-7-deazaguanine (preQ) for the biosynthesis of the tRNA-inserted nucleoside queuosine. The proposed QueF mechanism involves a covalent thioimide adduct between preQ and a cysteine nucleophile in the enzyme, and this adduct is subsequently converted into preQ in two NADPH-dependent reduction steps.

An investigation of nitrile transforming enzymes in the chemo-enzymatic synthesis of the taxol sidechain.

Paclitaxel (taxol) is an antimicrotubule agent widely used in the treatment of cancer. Taxol is prepared in a semisynthetic route by coupling the N-benzoyl-(2R,3S)-3-phenylisoserine sidechain to the baccatin III core structure. Precursors of the taxol sidechain have previously been prepared in chemoenzymatic approaches using acylases, lipases, and reductases, mostly featuring the enantioselective, enzymatic step early in the reaction pathway.

Targeting the substrate binding site of E. coli nitrile reductase QueF by modeling, substrate and enzyme engineering.

Nitrile reductase QueF catalyzes the reduction of 2-amino-5-cyanopyrrolo[2,3-d]pyrimidin-4-one (preQ0) to 2-amino-5-aminomethylpyrrolo[2,3-d]pyrimidin-4-one (preQ1) in the biosynthetic pathway of the hypermodified nucleoside queuosine. It is the only enzyme known to catalyze a reduction of a nitrile to its corresponding primary amine and could therefore expand the toolbox of biocatalytic reactions of nitriles. To evaluate this new oxidoreductase for application in biocatalytic reactions, investigation of its substrate scope is prerequisite.

Enantioseparation of nonproteinogenic amino acids.

The enantioseparation of structurally related N-protected beta-/gamma-amino acids, beta-/gamma-amino amides, and beta-/gamma-amino nitriles by using six different commercially available chiral stationary phases (CSPs) is reported. The synthetic key step to introduce stereochemical asymmetry into all compounds is an enzymatic kinetic resolution of the racemic nitriles to the respective amino amides and/or amino acids, depending on the class of enzyme (nitrile hydratase or nitrilase) applied. The separation efficiencies of all CSPs with regard to functional groups as well as structural variations of the amino acid derivatives depicted in Fig.

Influence of relative configuration of disubstituted cyclopentanes and -hexanes on 13C shifts.

(13)C shifts of disubstituted cyclopentane and cyclohexane derivatives were compared in dependence on the relative configuration of the two substituents. A diequatorial substitution correlates with deshielding compared to other substitution patterns. Some novel fluorinated cyclopentanes and -hexanes including their DFT calculation-assisted structure elucidation are described.

Nitrilases catalyze key step to conformationally constrained GABA analogous gamma-amino acids in high optical purity.

Five- and six-membered carbocyclic gamma-amino acids were prepared in high enantiomeric purity by nitrilase-mediated transformation of hitherto unreported gamma-amino nitriles. The nitrilases investigated reveal a strong enantiopreference for cis-isomers (up to 99% ee), whereas trans-isomers were available in up to 86% ee. The biocatalytic enantioselective syntheses of cis-3-aminocyclohexanecarboxylic acid (3b), trans-3-aminocyclohexanecarboxylic acids (4b, 6b, 8b) as well as trans-3-aminocylopentanecarboxylic acid (2b) are hereby reported for the first time.

Enzyme stabilizer DTT catalyzes nitrilase analogue hydrolysis of nitriles.

Amides are the dominating products in some nitrilase catalyzed conversions of alpha-activated nitriles, but unexpectedly this hydrolytic reaction is also catalyzed by 1,4-dithio-dl-threitol (DTT), a standard antioxidizing enzyme stabilizer.