A Multi-Enzyme Cascade for the Production of High-Value Aromatic Compounds

Cascade reactions are the basis of life in nature and are adapted to research and industry in an increasing manner. The focus of this study is the production of the high-value aromatic ester cinnamyl cinnamate, which can be applied in flavors and fragrances. A three-enzyme cascade was established to realize the synthesis, starting from the corresponding aldehyde with in situ cofactor regeneration in a two-phase system. After characterization of the enzymes, a screening with different organic solvents was carried out, whereby xylene was found to be the most suitable solvent for the second phase. The reaction stability of the formate dehydrogenase (FDH) from Candida boidinii is the limiting step during cofactor regeneration. However, the applied enzyme cascade showed an overall yield of 54%. After successful application on lab scale, the limitation by the FDH was overcome by immobilization of the enzymes and an optimized downstream process, transferring the cascade into a miniplant. The upscaling resulted in an increased yield for the esterification, as well as overall yields of 37%.

Fourier Transform Infrared Spectroscopy Analysis of Allium sativum L. and Nymphaea lotus L.

The use of Fourier Transforms Infrared Spectroscopy (FTIR) in screening secondary metabolites provides valuable information on qualitative, quantitative and the pattern of the biologically active compounds. The present study was carried out to identify functional groups present in water, methanol and n-hexane extracts of Allium sativum and Nymphaea lotus. It was revealed that Allium sativum and Nymphaea lotus possess numerous secondary metabolites {A. sativum L. (isothiocynate, acid halide, conjugated aldehyde, imine/oxime, halo compound, conjugated amine, alphaticprimary amine, aldehyde, anhydride, α,β-unsaturated ketone, carboxylic acid, nitro compound, aromatic ester) and N. lotus L. (aliphatic primary amine, halo compound, anhydride, vinyl ether, cabocylic acid, cyclic alkene, unsaturated ketone, aldehyde, aliphatic primary amine, aldehyde, alkane, benzene derivative, sulphide, alkene, akyl aryl ether, sulfonyl chloride, δ-lactone, imine/oxime, thiocyanate, amine salt, esters, alkene, nitro compound, sulphate, sulphone, akyl aryl ether, aromatic ester, fluoro compound, amine salt, sulphonyl chloride, tertiary alchohol, α,β-unsaturated ketone, alkyne, allene, sulfonic acid, α,β-unsaturated ester, alphatic primary amine, amine, sulfonyl chloride, vinyl ether, aromatic amine, alphatic ketone, isothiocyanate, thiocynate, conjugated alkene and anhydride)} that may be biologically active which could be useful in production of antimicrobials and other medicinal products that can be of high benefits in proffering reliable alternative medicine to human and animal diseases.

Divergent Synthesis of Monosubstituted and Unsymmetrical 3,6- Disubstituted Tetrazines from Carboxylic Ester Precursors

As tetrazines are important tools to the field of bioorthogonal chemistry, there is a need for new approaches to synthesize unsymmetrical and 3-monosubstituted tetrazines. Described here is a general, one-pot method for converting (3methyloxetan-3-yl)methyl carboxylic esters into 3thiomethyltetrazines. These versatile intermediates were applied as a platform for the synthesis of unsymmetrical tetrazines via Pdcatalyzed cross-coupling and in the first example of catalytic thioether reduction to access monosubstituted tetrazines. The method enables the development of new tetrazines possessing a favorable combination of kinetics, small size and hydrophilicity. The chemistry was applied to a broad range of aliphatic and aromatic ester precursors and to the synthesis of heterocycles including BODIPY fluorophores and biotin. In addition, a series of tetrazine probes for monoacylglycerol lipase (MAGL) were synthesized and the most reactive one was applied in labeling of endogenous MAGL in live cells<br>

Divergent Synthesis of Monosubstituted and Unsymmetrical 3,6- Disubstituted Tetrazines from Carboxylic Ester Precursors

As tetrazines are important tools to the field of bioorthogonal chemistry, there is a need for new approaches to synthesize unsymmetrical and 3-monosubstituted tetrazines. Described here is a general, one-pot method for converting (3methyloxetan-3-yl)methyl carboxylic esters into 3thiomethyltetrazines. These versatile intermediates were applied as a platform for the synthesis of unsymmetrical tetrazines via Pdcatalyzed cross-coupling and in the first example of catalytic thioether reduction to access monosubstituted tetrazines. The method enables the development of new tetrazines possessing a favorable combination of kinetics, small size and hydrophilicity. The chemistry was applied to a broad range of aliphatic and aromatic ester precursors and to the synthesis of heterocycles including BODIPY fluorophores and biotin. In addition, a series of tetrazine probes for monoacylglycerol lipase (MAGL) were synthesized and the most reactive one was applied in labeling of endogenous MAGL in live cells<br>

Ester Transfer Reaction of Aromatic Esters with Haloarenes and Arenols by a Nickel Catalyst

A catalytic ester transfer reaction of aromatic esters with aryl halides/arenols was developed. The present reaction can transfer an ester functional group from certain aromatic esters to haloarenes. This ester transfer reaction involves two oxidative additions­­— one from the C–C bond of the aromatic ester and one from the C–halogen bond of haloarenes— onto a nickel catalyst. The utilization of a Ni/dcypt catalyst capable of cleaving both chemical bonds was a key for the reaction progress. Furthermore, naphthol-based aryl electrophiles were also applicable to the catalytic system via C–O bond activation.

Ester Transfer Reaction of Aromatic Esters with Haloarenes and Arenols by a Nickel Catalyst

A catalytic ester transfer reaction of aromatic esters with aryl halides/arenols was developed. The present reaction can transfer an ester functional group from certain aromatic esters to haloarenes. This ester transfer reaction involves two oxidative additions­­— one from the C–C bond of the aromatic ester and one from the C–halogen bond of haloarenes— onto a nickel catalyst. The utilization of a Ni/dcypt catalyst capable of cleaving both chemical bonds was a key for the reaction progress. Furthermore, naphthol-based aryl electrophiles were also applicable to the catalytic system via C–O bond activation.

Synthesis, characterization, and properties of a novel aromatic ester-based polybenzoxazine

A novel benzoxazine monomer contain ester group was obtained by an indirect molecular design method. Its polymer showed excellent flexibility.