An Engineered Alcohol Oxidase for the Oxidation of Primary Alcohols

Tandem One-Pot Biocatalytic Oxidation and Wittig Reaction in Water

We explore biocatalytic aldehyde generation under aqueous conditions, concomitantly delivering access to a one-pot Wittig reaction using stabilized phosphoranes and granting diverse alkene products. Using a recombinant choline oxidase mutant, we first undertake biocatalytic alcohol oxidation across a range of functional aliphatic primary alcohols, demonstrating a remarkable substrate tolerance for this enzyme, including chloride, bromide, azide, S-methyl, and alkynyl groups. Following this, we extend capability and deliver a practicable milligram-scale one-pot Wittig reaction in water.

Enzymatic Synthesis of Unprotected α,β-Diamino Acids via Direct Asymmetric Mannich Reactions

α,β-Diamino acids are important structural motifs and building blocks for numerous bioactive natural products, peptidomimetics, and pharmaceuticals, yet efficient asymmetric synthesis to access these stereoarrays remains a challenge. Herein, we report the development of a pyridoxal 5'-phosphate (PLP)-dependent enzyme that is engineered to catalyze stereoselective Mannich-type reactions between free α-amino acids and enolizable cyclic imines. This biocatalyst enabled one-step asymmetric enzymatic synthesis of the unusual pyrrolidine-containing amino acid L-tambroline at gram-scale with high enantio- and diastereocontrol. Furthermore, this enzymatic platform is capable of utilizing a diverse range of α-amino acids as the Mannich donor and various cyclic imines as the acceptor. By coupling with different imine-generating enzymes, we established versatile biocatalytic cascades and demonstrated a general, concise, versatile, and atom-economic approach to access unprotected α,β-diamino acids, including structurally complex α,α-disubstituted α,β-diamino acids with contiguous stereocenters.

Peptide and Enzyme Catalysts Work in Concert in Stereoselective Cascade Reactions-Oxidation followed by Conjugate Addition

Enzymes and peptide catalysts consist of the same building blocks but require vastly different environments to operate best. Herein, we show that an enzyme and a peptide catalyst can work together in a single reaction vessel to catalyze a two-step cascade reaction with high chemo- and stereoselectivity. Abundant linear alcohols, nitroolefins, an alcohol oxidase, and a tripeptide catalyst provided chiral γ-nitroaldehydes in aqueous buffer. High yields (up to 92 %) and stereoselectivities (up to 98 % ee) were achieved for the cascade through the rational design of the peptide catalyst and the identification of common reaction conditions.

The in-silico study of the structural changes in the Arthrobacter globiformis choline oxidase induced by high temperature

BACKGROUND

Choline oxidase, a flavoprotein, is an enzyme that catalyzes the reaction which converts choline into glycine betaine. Choline oxidase started its journey way back in 1933. However, the impact of the high temperature on its structure has not been explored despite the long history and availability of its crystal structure. Both choline oxidase and its product, glycine betaine, have enormous applications spanning across multiple industries. Understanding how the 3D structure of the enzyme will change with the temperature change can open new ways to make it more stable and useful for industry.

PROCESS

This research paper presents the in-silico study and analysis of the structural changes of A. globiformis choline oxidase at temperatures from 25 °C to 60 °C. A step-wise process is depicted in Fig. 1.

RESULTS

Multiple sequence alignment (MSA) of 11 choline oxidase sequences from different bacteria vs Arthrobacter globiformis choline oxidase showed that active site residues are highly conserved. The available crystal structure of A. globiformis choline oxidase with cofactor Flavin Adenine Dinucleotide (FAD) in the dimeric state (PDB ID: 4MJW)1 was considered for molecular dynamics simulations. A simulated annealing option was used to gradually increase the temperature of the system from 25 °C to 60 °C. Analysis of the conserved residues, as well as residues involved in Flavin Adenine Dinucleotide (FAD) binding, substrate binding, substate gating, and dimer formationwas done. At high temperatures, the formation of the inter-chain salt bridge between Arg50 and Glu63 was a significant observation near the active site of choline oxidase.

CONCLUSION

Molecular dynamics studies suggest that an increase in temperature has a significant impact on the extended Flavin Adenine Dinucleotide (FAD) binding region. These changes interfere with the entry of substrate to the active site of the enzyme and make the enzyme inactive.

Harnessing a Biocatalyst to Bioremediate the Purification of Alkylglycosides

As the world moves towards net-zero carbon emissions, the development of sustainable chemical manufacturing processes is essential. Within manufacturing, purification by distillation is often used, however this process is energy intensive and methods that could obviate or reduce its use are desirable. Developed herein is an alternative, oxidative biocatalytic approach that enables purification of alkyl monoglucosides (essential bio-based surfactant components). Implementing an immobilised engineered alcohol oxidase, a long-chain alcohol by-product derived from alkyl monoglucoside synthesis (normally removed by distillation) is selectively oxidised to an aldehyde, conjugated to an amine resin and then removed by simple filtration. This affords recovery of the purified alkyl monoglucoside. The approach lays a blueprint for further development of sustainable alkylglycoside purification using biocatalysis and, importantly, for refining other important chemical feedstocks that currently rely on distillation.

Enzymatic Oxy- and Amino-Functionalization in Biocatalytic Cascade Synthesis: Recent Advances and Future Perspectives

Biocatalytic cascades are a powerful tool for building complex molecules containing oxygen and nitrogen functionalities. Moreover, the combination of multiple enzymes in one pot offers the possibility to minimize downstream processing and waste production. In this review, we illustrate various recent efforts in the development of multi-step syntheses involving C-O and C-N bond-forming enzymes to produce high value-added compounds, such as pharmaceuticals and polymer precursors. Both in vitro and in vivo examples are discussed, revealing the respective advantages and drawbacks. The use of engineered enzymes to boost the cascades outcome is also addressed and current co-substrate and cofactor recycling strategies are presented, highlighting the importance of atom economy. Finally, tools to overcome current challenges for multi-enzymatic oxy- and amino-functionalization reactions are discussed, including flow systems with immobilized biocatalysts and cascades in confined nanomaterials.

Enzymatic reactions towards aldehydes: An overview

Many aldehydes are volatile compounds with distinct and characteristic olfactory properties. The aldehydic functional group is reactive and, as such, an invaluable chemical multi-tool to make all sorts of products. Owing to the reactivity, the selective synthesis of aldehydic is a challenging task. Nature has evolved a number of enzymatic reactions to produce aldehydes, and this review provides an overview of aldehyde-forming reactions in biological systems and beyond. Whereas some of these biotransformations are still in their infancy in terms of synthetic applicability, others are developed to an extent that allows their implementation as industrial biocatalysts.

Three-Stage Conversion of Chemically Inert n-Heptane to α-Hydrazino Aldehyde Based on Bioelectrocatalytic C-H Bond Oxyfunctionalization

Simple petrochemical feedstocks are often the starting material for the synthesis of complex commodity and fine and specialty chemicals. Designing synthetic pathways for these complex and specific molecular structures with sufficient chemo-, regio-, enantio-, and diastereo-selectivity can expand the existing petrochemicals landscape. The two overarching challenges in designing such pathways are selective activation of chemically inert C-H bonds in hydrocarbons and systematic functionalization to synthesize complex structures. Multienzyme cascades are becoming a growing means of overcoming the first challenge. However, extending multienzyme cascade designs is restricted by the arsenal of enzymes currently at our disposal and the compatibility between specific enzymes. Here, we couple a bioelectrocatalytic multienzyme cascade to organocatalysis, which are two distinctly different classes of catalysis, in a single system to address both challenges. Based on the development and utilization of an anthraquinone (AQ)-based redox polymer, the bioelectrocatalytic step achieves regioselective terminal C-H bond oxyfunctionalization of chemically inert n-heptane. A second biocatalytic step selectively oxidizes the resulting 1-heptanol to heptanal. The succeeding inherently simple and durable l-proline-based organocatalysis step is a complementary partner to the multienzyme steps to further functionalize heptanal to the corresponding α-hydrazino aldehyde. The "three-stage" streamlined design exerts much control over the chemical conversion, which renders the collective system a versatile and adaptable model for a broader substrate scope and more complex C-H functionalization.

Properties, Physiological Functions and Involvement of Basidiomycetous Alcohol Oxidase in Wood Degradation

Extensive research efforts have been devoted to describing yeast alcohol oxidase (AO) and its promoter region, which is vastly applied in studies of heterologous gene expression. However, little is known about basidiomycetous AO and its physiological role in wood degradation. This review describes several alcohol oxidases from both white and brown rot fungi, highlighting their physicochemical and kinetic properties. Moreover, the review presents a detailed analysis of available AO-encoding gene promoter regions in basidiomycetous fungi with a discussion of the manipulations of culture conditions in relation to the modification of alcohol oxidase gene expression and changes in enzyme production. The analysis of reactions catalyzed by lignin-modifying enzymes (LME) and certain lignin auxiliary enzymes (LDA) elucidated the possible involvement of alcohol oxidase in the degradation of derivatives of this polymer. Combined data on lignin degradation pathways suggest that basidiomycetous AO is important in secondary reactions during lignin decomposition by wood degrading fungi. With numerous alcoholic substrates, the enzyme is probably engaged in a variety of catalytic reactions leading to the detoxification of compounds produced in lignin degradation processes and their utilization as a carbon source by fungal mycelium.

Efficient synthesis 1,4-cyclohexanedicarboxaldehyde by an engineered alcohol oxidase

In this study, we selected and engineered a flavin adenine dinucleotide (FAD)-dependent alcohol oxidase (AOX) to produce 1,4-cyclohexanedicarboxaldehyde (CHDA), an initial raw material for spiral compounds, from 1,4-cyclohexanedimethanol (CHDM). First, the structure of alcohol oxidase from Arthrobacter cholorphenolicus (AcCO) was analyzed, and the mechanism of AcCO-catalyzed primary alcohol oxidation was elucidated, demonstrating that the energy barrier of the hydride (H-) transfer (13.4 kcal·mol-1 and 20.4 kcal·mol-1) decreases the catalytic efficiency of the primary alcohol oxidation reaction. Therefore, we designed a protein engineering strategy to adjust the catalytically active conformation to shorten the distance of hydride (H-) transfer and further decreased the core energy barrier. Following this strategy, variant W4 (S101A/H351V/N378S/Q329N) was obtained with 112.5-fold increased catalytic efficiency to produce CHDA compared to that of the wild-type strain. The 3 L scale preparation of CHDA reached a titer up to 29.6 g·L-1 with a 42.2% yield by an Escherichia coli whole-cell catalyst, which demonstrates the potential of this system for industrial application.

An Engineered Cholesterol Oxidase Catalyses Enantioselective Oxidation of Non-steroidal Secondary Alcohols

The enantioselective oxidation of 2° alcohols to ketones is an important reaction in synthetic chemistry, especially if it can be achieved using O2 -driven alcohol oxidases under mild reaction conditions. However to date, oxidation of secondary alcohols using alcohol oxidases has focused on activated benzylic or allylic substrates, with unactivated secondary alcohols showing poor activity. Here we show that cholesterol oxidase (EC 1.1.3.6) could be engineered for activity towards a range of aliphatic, cyclic, acyclic, allylic and benzylic secondary alcohols. Additionally, since the variants demonstrated high (S)-selectivity, deracemisation reactions were performed in the presence of ammonia borane to obtain enantiopure (R)-alcohols.

High-Yield Synthesis of Enantiopure 1,2-Amino Alcohols from l-Phenylalanine via Linear and Divergent Enzymatic Cascades

Enantiomerically pure 1,2-amino alcohols are important compounds due to their biological activities and wide applications in chemical synthesis. In this work, we present two multienzyme pathways for the conversion of l-phenylalanine into either 2-phenylglycinol or phenylethanolamine in the enantiomerically pure form. Both pathways start with the two-pot sequential four-step conversion of l-phenylalanine into styrene via subsequent deamination, decarboxylation, enantioselective epoxidation, and enantioselective hydrolysis. For instance, after optimization, the multienzyme process could convert 507 mg of l-phenylalanine into (R)-1-phenyl-1,2-diol in an overall isolated yield of 75% and >99% ee. The opposite enantiomer, (S)-1-phenyl-1,2-diol, was also obtained in a 70% yield and 98–99% ee following the same approach. At this stage, two divergent routes were developed to convert the chiral diols into either 2-phenylglycinol or phenylethanolamine. The former route consisted of a one-pot concurrent interconnected two-step cascade in which the diol intermediate was oxidized to 2-hydroxy-acetophenone by an alcohol dehydrogenase and then aminated by a transaminase to give enantiomerically pure 2-phenylglycinol. Notably, the addition of an alanine dehydrogenase enabled the connection of the two steps and made the overall process redox-self-sufficient. Thus, (S)-phenylglycinol was isolated in an 81% yield and >99.4% ee starting from ca. 100 mg of the diol intermediate. The second route consisted of a one-pot concurrent two-step cascade in which the oxidative and reductive steps were not interconnected. In this case, the diol intermediate was oxidized to either (S)- or (R)-2-hydroxy-2-phenylacetaldehyde by an alcohol oxidase and then aminated by an amine dehydrogenase to give the enantiomerically pure phenylethanolamine. The addition of a formate dehydrogenase and sodium formate was required to provide the reducing equivalents for the reductive amination step. Thus, (R)-phenylethanolamine was isolated in a 92% yield and >99.9% ee starting from ca. 100 mg of the diol intermediate. In summary, l-phenylalanine was converted into enantiomerically pure 2-phenylglycinol and phenylethanolamine in overall yields of 61% and 69%, respectively. This work exemplifies how linear and divergent enzyme cascades can enable the synthesis of high-value chiral molecules such as amino alcohols from a renewable material such as l-phenylalanine with high atom economy and improved sustainability.

Reaching New Biocatalytic Reactivity Using Continuous Flow Reactors

The use of flow reactors in biocatalysis has increased significantly in recent years. Chemists have begun to design flow systems that even allow new biocatalytic reactions to take place. This concept article will focus on the design of flow systems that have allowed enzymes to go beyond their limits in batch. The case is made for moving towards fully continuous systems. With flow chemistry increasingly seen as an enabling technology for automated synthesis, and with advancements in AI-assisted enzyme design, there is a real possibility to fully automate the development and implementation of a continuous biocatalytic processes. This will lead to significantly improved enzyme processes for synthesis.

α-Dioxygenases (α-DOXs): Promising biocatalysts for the environmentally friendly production of aroma compounds

Fatty aldehydes (FALs) can be derived from fatty acids (FAs) and related compounds and are frequently used as flavors and fragrances. Although chemical methods have been conventionally used, their selective biotechnological production aiming at more efficient and eco‐friendly synthetic routes is in demand. α‐Dioxygenases (α‐DOXs) are heme‐dependent oxidative enzymes biologically involved in the initial step of plant FA α‐oxidation during which molecular oxygen is incorporated into the C_α‐position of a FA (C_n) to generate the intermediate FA hydroperoxide, which is subsequently converted into the shortened corresponding FAL (C_n‐1). α‐DOXs are promising biocatalysts for the flavor and fragrance industries, they do not require NAD(P)H as cofactors or redox partner proteins, and they have a broad substrate scope. Here, we highlight recent advances in the biocatalytic utilization of α‐DOXs with emphasis on newly discovered cyanobacterial α‐DOXs as well as analytical methods to measure α‐DOX activity in vitro and in vivo.

Development of Continuous Flow Systems to Access Secondary Amines Through Previously Incompatible Biocatalytic Cascades*

A key aim of biocatalysis is to mimic the ability of eukaryotic cells to carry out multistep cascades in a controlled and selective way. As biocatalytic cascades get more complex, reactions become unattainable under typical batch conditions. Here a number of continuous flow systems were used to overcome batch incompatibility, thus allowing for successful biocatalytic cascades. As proof-of-principle, reactive carbonyl intermediates were generated in situ using alcohol oxidases, then passed directly to a series of packed-bed modules containing different aminating biocatalysts which accordingly produced a range of structurally distinct amines. The method was expanded to employ a batch incompatible sequential amination cascade via an oxidase/transaminase/imine reductase sequence, introducing different amine reagents at each step without cross-reactivity. The combined approaches allowed for the biocatalytic synthesis of the natural product 4O-methylnorbelladine.

Development of Continuous Flow Systems to Access Secondary Amines Through Previously Incompatible Biocatalytic Cascades

A key aim of biocatalysis is to mimic the ability of eukaryotic cells to carry out multistep cascades in a controlled and selective way. As biocatalytic cascades get more complex, reactions become unattainable under typical batch conditions. Here a number of continuous flow systems were used to overcome batch incompatibility, thus allowing for successful biocatalytic cascades. As proof-of-principle, reactive carbonyl intermediates were generated in situ using alcohol oxidases, then passed directly to a series of packed-bed modules containing different aminating biocatalysts which accordingly produced a range of structurally distinct amines. The method was expanded to employ a batch incompatible sequential amination cascade via an oxidase/transaminase/imine reductase sequence, introducing different amine reagents at each step without cross-reactivity. The combined approaches allowed for the biocatalytic synthesis of the natural product 4O-methylnorbelladine.

LuxAB-Based Microbial Cell Factories for the Sensing, Manufacturing and Transformation of Industrial Aldehydes

The application of genetically encoded biosensors enables the detection of small molecules in living cells and has facilitated the characterization of enzymes, their directed evolution and the engineering of (natural) metabolic pathways. In this work, the LuxAB biosensor system from Photorhabdus luminescens was implemented in Escherichia coli to monitor the enzymatic production of aldehydes from primary alcohols and carboxylic acid substrates. A simple high-throughput assay utilized the bacterial luciferase—previously reported to only accept aliphatic long-chain aldehydes—to detect structurally diverse aldehydes, including aromatic and monoterpene aldehydes. LuxAB was used to screen the substrate scopes of three prokaryotic oxidoreductases: an alcohol dehydrogenase (Pseudomonas putida), a choline oxidase variant (Arthrobacter chlorophenolicus) and a carboxylic acid reductase (Mycobacterium marinum). Consequently, high-value aldehydes such as cinnamaldehyde, citral and citronellal could be produced in vivo in up to 80% yield. Furthermore, the dual role of LuxAB as sensor and monooxygenase, emitting bioluminescence through the oxidation of aldehydes to the corresponding carboxylates, promises implementation in artificial enzyme cascades for the synthesis of carboxylic acids. These findings advance the bio-based detection, preparation and transformation of industrially important aldehydes in living cells.

Predicting enzymatic reactions with a molecular transformer

The use of enzymes for organic synthesis allows for simplified, more economical and selective synthetic routes not accessible to conventional reagents. However, predicting whether a particular molecule might undergo a specific enzyme transformation is very difficult. Here we used multi-task transfer learning to train the molecular transformer, a sequence-to-sequence machine learning model, with one million reactions from the US Patent Office (USPTO) database combined with 32 181 enzymatic transformations annotated with a text description of the enzyme. The resulting enzymatic transformer model predicts the structure and stereochemistry of enzyme-catalyzed reaction products with remarkable accuracy. One of the key novelties is that we combined the reaction SMILES language of only 405 atomic tokens with thousands of human language tokens describing the enzymes, such that our enzymatic transformer not only learned to interpret SMILES, but also the natural language as used by human experts to describe enzymes and their mutations.

RetroBioCat as a computer-aided synthesis planning tool for biocatalytic reactions and cascades

As the enzyme toolbox for biocatalysis has expanded, so has the potential for the construction of powerful enzymatic cascades for efficient and selective synthesis of target molecules. Additionally, recent advances in computer-aided synthesis planning are revolutionising synthesis design in both synthetic biology and organic chemistry. However, the potential for biocatalysis is not well captured by tools currently available in either field. Here we present RetroBioCat, an intuitive and accessible tool for computer-aided design of biocatalytic cascades, freely available at retrobiocat.com. Our approach uses a set of expertly encoded reaction rules encompassing the enzyme toolbox for biocatalysis, and a system for identifying literature precedent for enzymes with the correct substrate specificity where this is available. Applying these rules for automated biocatalytic retrosynthesis, we show our tool to be capable of identifying promising biocatalytic pathways to target molecules, validated using a test-set of recent cascades described in the literature.

Biocatalysis: Enzymatic Synthesis for Industrial Applications

Biocatalysis has found numerous applications in various fields as an alternative to chemical catalysis. The use of enzymes in organic synthesis, especially to make chiral compounds for pharmaceuticals as well for the flavors and fragrance industry, are the most prominent examples. In addition, biocatalysts are used on a large scale to make specialty and even bulk chemicals. This review intends to give illustrative examples in this field with a special focus on scalable chemical production using enzymes. It also discusses the opportunities and limitations of enzymatic syntheses using distinct examples and provides an outlook on emerging enzyme classes.

Biocatalysis in the Swiss Manufacturing Environment

Biocatalysis has undergone a remarkable transition in the last two decades, from being considered a niche technology to playing a much more relevant role in organic synthesis today. Advances in molecular biology and bioinformatics, and the decreasing costs for gene synthesis and sequencing contribute to the growing success of engineered biocatalysts in industrial applications. However, the incorporation of biocatalytic process steps in new or established manufacturing routes is not always straightforward. To realize the full synthetic potential of biocatalysis for the sustainable manufacture of chemical building blocks, it is therefore important to regularly analyze the success factors and existing hurdles for the implementation of enzymes in large scale small molecule synthesis. Building on our previous analysis of biocatalysis in the Swiss manufacturing environment, we present a follow-up study on how the industrial biocatalysis situation in Switzerland has evolved in the last four years. Considering the current industrial landscape, we record recent advances in biocatalysis in Switzerland as well as give suggestions where enzymatic transformations may be valuably employed to address some of the societal challenges we face today, particularly in the context of the current Coronavirus disease 2019 (COVID-19) pandemic.

Point-of-care assay for drunken driving with Pd@Pt core-shell nanoparticles-decorated ploy(vinyl alcohol) aerogel assisted by portable pressure meter

Alcohol abuse causes health problems and security accidents. A reliable and sensitive detection system for alcohol has been an instinctive demand in law enforcement and forensic. More efforts are demanded in developing new sensing strategy preferably with portable and non-invasive traits for the pushforward of point-of-care (POC) device popularization.

Methods: We developed a POC diagnosis system for alcohol assay with the aid of alcohol oxidase (AOX) pre-joining in the system as well as Pd@Pt core-shell nanoparticles (abbreviated to Pd@Pt) that were decorated on ploy(vinyl alcohol) aerogel with amphiphilicity. Biological samples like saliva and whole blood can be absorbed by the aerogel in a quick process, in which the analyte would go through a transformation from alcohol, H₂O₂, to a final production of O₂, causing an analyte dose-dependent signal change in the commercial portable pressure meter. The cascade reactions are readily catalyzed by AOX and Pd@Pt, of which the latter one possesses excellent peroxidase-like activity.

Results: Our design has smartness embodied in the aerogel circumvents the interference from methanol which is more ready to be catalyzed by AOX. Under the optimal conditions, the limit of detection for alcohol was 0.50 mM in saliva, and is able to distinguish the driving under the influence (DUI) (1.74 mM in saliva) and driving while impaired (DWI) (6.95 mM in saliva) in the national standard of China.

Conclusion: Our proof-of-concept study provides the possibility for the establishment of POC device for alcohol and other target detection, not only owing to the sensing qualification but also thanks to the architecture of such sensor that has great flexibility by replacing the AOX with glucose oxidase (GOX), thenceforth realizing the accurate detection of glucose in 0.5% whole blood sample. With the advantages of easy accessibility and anti-interference ability, our sensor exhibits great potential for quantitative diagnostics in biological system.

Production of Hydroxy Acids: Selective Double Oxidation of Diols by Flavoprotein Alcohol Oxidase

Flavoprotein oxidases can catalyze oxidations of alcohols and amines by merely using molecular oxygen as the oxidant, making this class of enzymes appealing for biocatalysis. The FAD-containing (FAD=flavin adenine dinucleotide) alcohol oxidase from P. chrysosporium facilitated double and triple oxidations for a range of aliphatic diols. Interestingly, depending on the diol substrate, these reactions result in formation of either lactones or hydroxy acids. For example, diethylene glycol could be selectively and fully converted into 2-(2-hydroxyethoxy)acetic acid. Such a facile cofactor-independent biocatalytic route towards hydroxy acids opens up new avenues for the preparation of polyester building blocks.

Catalytic Oxidations in a Bio-Based Economy

The role of bio- and chemo-catalytic aerobic oxidations in the production of commodity chemicals in a bio-refinery is reviewed. The situation is fundamentally different to that in a petrochemicals refinery where the feedstocks are gaseous or liquid hydrocarbons that are oxidized at elevated temperatures in the vapor or liquid phase under solvent-free conditions. In contrast, the feedstocks in a biorefinery are carbohydrates that are water soluble solids and their conversion will largely involve aerobic oxidations of hydroxyl functional groups in water as the solvent under relatively mild conditions of temperature and pressure. This will require the development and use of cost-effective and environmentally attractive processes using both chemo- and biocatalytic methods for alcohols and polyols.

Biocatalytic Enantioselective Oxidation of Sec-Allylic Alcohols with Flavin-Dependent Oxidases

The oxidation of allylic alcohols is challenging to perform in a chemo- as well as stereo-selective fashion at the expense of molecular oxygen using conventional chemical protocols. Here, we report the identification of a library of flavin-dependent oxidases including variants of the berberine bridge enzyme (BBE) analogue from Arabidopsis thaliana (AtBBE15) and the 5-(hydroxymethyl)furfural oxidase (HMFO) and its variants (V465T, V465S, V465T/W466H and V367R/W466F) for the enantioselective oxidation of sec-allylic alcohols. While primary and benzylic alcohols as well as certain sugars are well known to be transformed by flavin-dependent oxidases, sec-allylic alcohols have not been studied yet except in a single report. The model substrates investigated were oxidized enantioselectively in a kinetic resolution with an E-value of up to >200. For instance HMFO V465S/T oxidized the (S)-enantiomer of (E)-oct-3-en-2-ol (1 a) and (E)-4-phenylbut-3-en-2-ol with E>200 giving the remaining (R)-alcohol with ee>99% at 50% conversion. The enantioselectivity could be decreased if required by medium engineering by the addition of cosolvents (e. g. dimethyl sulfoxide).