Fatma Feyza Özgen

Bio: Fatma Feyza Özgen is an academic researcher from Graz University of Technology. The author has contributed to research in topics: Catalysis & Chemistry. The author has an hindex of 4, co-authored 6 publications receiving 128 citations. Previous affiliations of Fatma Feyza Özgen include University of Groningen & California State University, Stanislaus.

Photo-Biocatalysis: Biotransformations in the Presence of Light

Abstract: Light has received increased attention for various chemical reactions but also in combination with biocatalytic reactions. Because currently only a few enzymatic reactions are known, which per se require light, most transformations involving light and a biocatalyst exploit light either for providing the cosubstrate or cofactor in an appropriate redox state for the biotransformation. In selected cases, a promiscuous activity of known enzymes in the presence of light could be induced. In other approaches, light-induced chemical reactions have been combined with a biocatalytic step, or light-induced biocatalytic reactions were combined with chemical reactions in a linear cascade. Finally, enzymes with a light switchable moiety have been investigated to turn off/on or tune the actual reaction. This Review gives an overview of the various approaches for using light in biocatalysis.

Photo-biocatalytic Cascades: Combining Chemical and Enzymatic Transformations Fueled by Light.

Abstract: In the field of green chemistry, light - an attractive natural agent - has received particular attention for driving biocatalytic reactions. Moreover, the implementation of light to drive (chemo)enzymatic cascade reactions opens up a golden window of opportunities. However, there are limitations to many current examples, mostly associated with incompatibility between the enzyme and the photocatalyst. Additionally, the formation of reactive radicals upon illumination and the loss of catalytic activities in the presence of required additives are common observations. As outlined in this review, the main question is how to overcome current challenges to the exploitation of light to drive (chemo)enzymatic transformations. First, we highlight general concepts in photo-biocatalysis, then give various examples of photo-chemoenzymatic (PCE) cascades, further summarize current synthetic examples of PCE cascades and discuss strategies to address the limitations.

Artificial Light-Harvesting Complexes Enable Rieske Oxygenase Catalyzed Hydroxylations in Non-Photosynthetic cells.

Abstract: In this study, we coupled a well-established whole-cell system based on E. coli via light-harvesting complexes to Rieske oxygenase (RO)-catalyzed hydroxylations in vivo. Although these enzymes represent very promising biocatalysts, their practical applicability is hampered by their dependency on NAD(P)H as well as their multicomponent nature and intrinsic instability in cell-free systems. In order to explore the boundaries of E. coli as chassis for artificial photosynthesis, and due to the reported instability of ROs, we used these challenging enzymes as a model system. The light-driven approach relies on light-harvesting complexes such as eosin Y, 5(6)-carboxyeosin, and rose bengal and sacrificial electron donors (EDTA, MOPS, and MES) that were easily taken up by the cells. The obtained product formations of up to 1.3 g L-1 and rates of up to 1.6 mm h-1 demonstrate that this is a comparable approach to typical whole-cell transformations in E. coli. The applicability of this photocatalytic synthesis has been demonstrated and represents the first example of a photoinduced RO system.

Rieske Non-Heme Iron Dioxygenases: Applications and Future Perspectives

Abstract: The stereo- and regioselective oxidative functionalization of olefins is amongst the most challenging reactions in organic syntheses. In particular, the catalytic asymmetric dihydroxylation of alkenes has attracted considerable attention due to the facile further transformation of the chiral diol products into valuable derivatives, making them important building blocks for the pharmaceutical and chemical industry. Nature’s creativity in developing solutions for C–H-bond functionalization reactions like hydroxylations at activated or non-activated C–H-bonds is remarkably shown by an impressive list of metal-dependent enzymes. These enzymes, like the Rieske non-heme iron oxygenases (ROs) are able to activate molecular oxygen in order to generate reactive oxygen species capable of hydroxylating alkyl-substrates and they also promote further oxidative transformations. For many of these reactions no ‘classical’ chemical counterpart is known. ROs represent promising biocatalysts for these reactions since they are the only enzymes known to catalyze the stereoselective formation of vicinal cis-diols in one step. They are soluble multicomponent systems that harness the reductive power of NAD(P)H for oxygen activation. Due to their versatility, ROs are considered as the non-heme analogues of cytochrome P450 monooxygenases and, in addition to their relaxed substrate specificity, these enzymes can also catalyze various oxidation reactions, resulting in an enormous potential of these enzymes for manifold synthetically useful transformations. This chapter describes the current understanding of the structural determinants and the catalytic behavior of dioxygenase-catalyzed reactions, and highlights how in several cases this knowledge has been harnessed to design tailored catalysts for the synthesis of various natural products, polyfunctionalized metabolites and pharmaceutical intermediates. Moreover, the chapter also gives insights into recently characterized ROs catalyzing unusual reactions as well as applications in chemo-enzymatic cascade reactions for natural product synthesis.

The Synthesis of Chiral γ‐Lactones by Merging Decatungstate Photocatalysis with Biocatalysis

Abstract: The implementation of light‐driven catalytic processes in biocatalysis opens a golden window of opportunities. We hereby report the merging of photocatalytic C−C bond formation with enzymatic asymmetric reduction for the direct conversion of simple aldehydes and acrylates or unsaturated carboxylic acids into chiral γ‐lactones. Tetrabutylammonium decatungstate (TBADT) is employed as the photocatalyst to trigger the hydroacylation of the starting olefins, yielding the corresponding keto esters/acids. Subsequently, an alcohol dehydrogenase converts the intermediate to the chiral alcohol, which undergoes lactonization to the desired γ‐lactone. The photochemoenzymatic synthesis of aliphatic and aromatic γ‐lactones was thereby achieved with up to >99 % ee and >99 % yield. This synthesis highlights the power of building molecular complexity by merging photocatalysis with biocatalysis to access high‐value added chiral compounds from simple, cheap and largely available starting materials.

Synthetic Methods Driven by the Photoactivity of Electron Donor-Acceptor Complexes

Abstract: The association of an electron-rich substrate with an electron-accepting molecule can generate a new molecular aggregate in the ground state, called an electron donor–acceptor (EDA) complex. Even w...

Microbial lipases and their industrial applications: a comprehensive review

Abstract: Lipases are very versatile enzymes, and produced the attention of the several industrial processes. Lipase can be achieved from several sources, animal, vegetable, and microbiological. The uses of microbial lipase market is estimated to be USD 425.0 Million in 2018 and it is projected to reach USD 590.2 Million by 2023, growing at a CAGR of 6.8% from 2018. Microbial lipases (EC 3.1.1.3) catalyze the hydrolysis of long chain triglycerides. The microbial origins of lipase enzymes are logically dynamic and proficient also have an extensive range of industrial uses with the manufacturing of altered molecules. The unique lipase (triacylglycerol acyl hydrolase) enzymes catalyzed the hydrolysis, esterification and alcoholysis reactions. Immobilization has made the use of microbial lipases accomplish its best performance and hence suitable for several reactions and need to enhance aroma to the immobilization processes. Immobilized enzymes depend on the immobilization technique and the carrier type. The choice of the carrier concerns usually the biocompatibility, chemical and thermal stability, and insolubility under reaction conditions, capability of easy rejuvenation and reusability, as well as cost proficiency. Bacillus spp., Achromobacter spp., Alcaligenes spp., Arthrobacter spp., Pseudomonos spp., of bacteria and Penicillium spp., Fusarium spp., Aspergillus spp., of fungi are screened large scale for lipase production. Lipases as multipurpose biological catalyst has given a favorable vision in meeting the needs for several industries such as biodiesel, foods and drinks, leather, textile, detergents, pharmaceuticals and medicals. This review represents a discussion on microbial sources of lipases, immobilization methods increased productivity at market profitability and reduce logistical liability on the environment and user.

Late-stage C-H functionalization offers new opportunities in drug discovery

Abstract: Over the past decade, the landscape of molecular synthesis has gained major impetus by the introduction of late-stage functionalization (LSF) methodologies. C–H functionalization approaches, particularly, set the stage for new retrosynthetic disconnections, while leading to improvements in resource economy. A variety of innovative techniques have been successfully applied to the C–H diversification of pharmaceuticals, and these key developments have enabled medicinal chemists to integrate LSF strategies in their drug discovery programmes. This Review highlights the significant advances achieved in the late-stage C–H functionalization of drugs and drug-like compounds, and showcases how the implementation of these modern strategies allows increased efficiency in the drug discovery process. Representative examples are examined and classified by mechanistic patterns involving directed or innate C–H functionalization, as well as emerging reaction manifolds, such as electrosynthesis and biocatalysis, among others. Structurally complex bioactive entities beyond small molecules are also covered, including diversification in the new modalities sphere. The challenges and limitations of current LSF methods are critically assessed, and avenues for future improvements of this rapidly expanding field are discussed. We, hereby, aim to provide a toolbox for chemists in academia as well as industrial practitioners, and introduce guiding principles for the application of LSF strategies to access new molecules of interest. Late-stage C–H functionalization of complex molecules has emerged as a powerful tool in drug discovery. This Review classifies significant examples by reaction manifold and assesses the benefits and challenges of each approach. Avenues for future improvements of this fast-expanding field are proposed.

Photoexcitation of flavoenzymes enables a stereoselective radical cyclization

Abstract: Photoexcitation is a common strategy for initiating radical reactions in chemical synthesis. We found that photoexcitation of flavin-dependent “ene”-reductases changes their catalytic function, enabling these enzymes to promote an asymmetric radical cyclization. This reactivity enables the construction of five-, six-, seven-, and eight-membered lactams with stereochemical preference conferred by the enzyme active site. After formation of a prochiral radical, the enzyme guides the delivery of a hydrogen atom from flavin—a challenging feat for small-molecule chemical reagents. The initial electron transfer occurs through direct excitation of an electron donor-acceptor complex that forms between the substrate and the reduced flavin cofactor within the enzyme active site. Photoexcitation of promiscuous flavoenzymes has thus furnished a previously unknown biocatalytic reaction.

Visible light photocatalysis in the late-stage functionalization of pharmaceutically relevant compounds.

Abstract: The late stage functionalization (LSF) of complex biorelevant compounds is a powerful tool to speed up the identification of structure-activity relationships (SARs) and to optimize ADME profiles. To this end, visible-light photocatalysis offers unique opportunities to achieve smooth and clean functionalization of drugs by unlocking site-specific reactivities under generally mild reaction conditions. This review offers a critical assessment of current literature, pointing out the recent developments in the field while emphasizing the expected future progress and potential applications. Along with paragraphs discussing the visible-light photocatalytic synthetic protocols so far available for LSF of drugs and drug candidates, useful and readily accessible synoptic tables of such transformations, divided by functional groups, will be provided, thus enabling a useful, fast, and easy reference to them.