Translating Planar Heterocycles into Three-Dimensional Analogs by Photoinduced Hydrocarboxylation**

The rapid preparation of complex three-dimensional (3D) heterocyclic scaffolds is a key challenge in modern medicinal chemistry. Despite the increased probability of clinical success for small molecule therapeutic candidates with increased 3D complexity, new drug targets remain dominated by flat molecules due to the abundance of coupling reactions available for their construction. In principle, heteroarene hydrofunctionalization reactions offer an opportunity to transform readily accessible planar molecules into more three-dimensionally complex analogs through the introduction of a single molecular vector. Unfortunately, dearomative hydrofunctionalization reactions remain limited. Herein, we report a new strategy to enable the dearomative hydrocarboxylation of indoles and related heterocycles. This reaction represents a rare example of a heteroarene hydrofunctionalization that meets the numerous requirements for broad implementation in drug discovery. The transformation is highly chemoselective, broad in scope, operationally simple, and readily amenable to high-throughput experimentation (HTE). Accordingly, this process will allow existing libraries of heteroaromatic compounds to be translated into diverse 3D analogs and enable exploration of new classes of medicinally relevant molecules.     

基于微流控技术的细胞水平高通量药物筛选系统的研究进展

药物筛选是新药研发的关键步骤,创新药物的发现需要采用适当的药物作用靶点对大量化合物样品进行筛选.高通量筛选系统能够实现数千个反应同时测试和分析,大大提高了药物筛选的实验规模和效率.其中基于细胞水平的高通量药物筛选系统因为更加接近人体生理条件,成为主要的筛选模式.而目前发展成熟的高通量细胞筛选系统主要基于多孔板,存在细胞...     

Catalytic Enantioselective Radical Transformations Enabled by Visible Light

Visible light has been recognized as an economical and environmentally benign source of energy that enables chemoselective molecular activation of chemical reactions and hence reveal a new horizon for the design and discovery of novel chemical transformations. On the other hand, asymmetric catalysis represents an economic method to satisfy the increasing need for enantioenriched compounds in the chemical and pharmaceutical industries. Therefore, combining visible light photocatalysis with asymmetric catalysis creates a wider range of opportunities for the development of mechanistically unique reaction schemes. However, there arise two main problems like undesirable photochemical background reactions and difficulties in controlling the stereochemistry with highly reactive photochemical intermediates which can pose a serious challenge to the development of asymmetric visible light photocatalysis. In recent years, several methods have been developed to overcome these challenges. This review summarizes the recent advances in visible light‐induced enantioselective reactions. We divide our discussion into four categories: Asymmetric photoredox organocatalysis, asymmetric transition metal photoredox catalysis, asymmetric photoredox Lewis acid catalysis and asymmetric photoinduced energy transfer catalysis. Special emphasis has been given to different catalytic activation modes that enable the construction of challenging carbon‐carbon and carbon‐heteroatom bond in an enantioselective fashion. A brief analysis of substrate scope and limitation as well as reaction mechanism of these reactions has been included.     

Bioluminescence and chemiluminescence in drug screening

Drug screening, that is, the evaluation of the biological activity of candidate drug molecules, is a key step in the drug discovery and development process. In recent years, high-throughput screening assays have become indispensable for early stage drug discovery because of the developments in synthesis technologies, such as combinatorial chemistry and automated synthesis, and the discovery of an increasing number of new pharmacological targets.Bioluminescence and chemiluminescence represent suitable detection techniques for high-throughput screening because they allow rapid and sensitive detection of the analytes and can be applied to small-volume samples. In this paper we report on recent applications of bioluminescence and chemiluminescence in drug screening, both for in vitro and in vivo assays. Particular attention is devoted to the latest and most innovative bioluminescence and chemiluminescence-based technologies for drug screening, such as assays based on genetically modified cells, bioluminescence resonance energy transfer (BRET)-based assays, and in vivo imaging assays using transgenic animals or bioluminescent markers. The possible relevance of bioluminescence and chemiluminescence techniques in the future developments of high-throughput screening technologies is also discussed.     

Application of microflow conditions to visible light photoredox catalysis

Applications of microflow conditions for visible light photoredox catalysis have successfully been developed. Operationally simple microreactor and FEP (fluorinated ethylene propylene copolymer) tube reactor systems enable significant improvement of several photoredox reactions using different photocatalysts such as [Ru(bpy)(3)](2+) and Eosin Y. Apart from rate acceleration, this approach facilitates previously challenging transformations of nonstabilized intermediates. Additionally, the productivity of the synergistic, catalytic enantioselective photoredox α-alkylation of aldehydes was demonstrated to be increased by 2 orders of magnitude.     

One-pot synthesis of tricyclo-1,4-benzoxazines via visible-light photoredox catalysis in continuous flow

A facile one-pot synthesis of tricyclo-1,4-benzoxazines has been developed via metal-free intramolecular cyclization of indole derivates. These reactions were efficiently achieved at ambient temperature by using visible-light photoredox catalysis in continuous flow. This directed intramolecular cyclization could be easily handled and scaled up in an open flask, enabling construction of a focused compound library for further pharmacological evaluation.     

High-Throughput Platform for Novel Reaction Discovery

Detecting the formation of new chemical bonds in high-throughput synthesis is limited by the efficiency and scalability of reaction product detection, as conventional methods for isolating product from reaction mixtures are time consuming and labor intensive. Here, we report a miniaturizable purification method that enables the rapid, high-throughput isolation of quaternary ammonium-tagged products from reaction mixtures with excellent purity using inexpensive equipment that easily can be set up in a typical organic chemistry laboratory. This novel purification technique enabled us to establish a high-throughput reaction discovery platform. We validated this platform in a screen of 1536 reactions, and one previously unreported transformation was identified.     

多组分反应在合成含肽类药物开发中的应用

多组分反应可以快速大量的合成结构复杂的药物分子,因此现代药物开发与多组分反应的发展密切相关。本文总结了近年来国内外有关多组分反应研究的发展概况及其在含肽链类新药物开发中的应用研究进展。     

Microfabricated analytical systems for integrated cancer cytomics

Tracking and understanding cell-to-cell variability is fundamental for systems biology, cytomics and computational modelling that aids e.g. anti-cancer drug discovery. Limitations of conventional cell-based techniques, such as flow cytometry and single cell imaging, however, make the high-throughput dynamic analysis on cellular and subcellular processes tedious and exceedingly expensive. The development of microfluidic lab-on-a-chip technologies is one of the most innovative and cost-effective approaches towards integrated cytomics. Lab-on-a-chip devices promise greatly reduced costs, increased sensitivity and ultrahigh throughput by implementing parallel sample processing. The application of laminar fluid flow under low Reynolds numbers provides an attractive analytical avenue for the rapid delivery and exchange of reagents with exceptional accuracy. Under these conditions, the fluid flow has no inertia, enabling the precise dosing of drugs, both spatially and temporally. In addition, by confining the dimensions of the microfluidic structure, it is possible to facilitate the precise sequential delivery of drugs and/or functional probes into the cellular systems. As only low cell numbers and operational reagent volumes are required, high-throughput integrated cytomics on a single cell level finally appears within the reach of clinical diagnostics and drug screening routines. Lab-on-a-chip microfluidic technologies therefore provide new opportunities for the development of content-rich personalized clinical diagnostics and cost-effective drug discovery. It is largely anticipated that advances in microfluidic technologies should aid in tailoring of investigational therapies and support the current computational efforts in systems biology.     

Photoredox catalysis on unactivated substrates with strongly reducing iridium photosensitizers

Photoredox catalysis has emerged as a powerful strategy in synthetic organic chemistry, but substrates that are difficult to reduce either require complex reaction conditions or are not amenable at all to photoredox transformations. In this work, we show that strong bis-cyclometalated iridium photoreductants with electron-rich β-diketiminate (NacNac) ancillary ligands enable high-yielding photoredox transformations of challenging substrates with very simple reaction conditions that require only a single sacrificial reagent. Using blue or green visible-light activation we demonstrate a variety of reactions, which include hydrodehalogenation, cyclization, intramolecular radical addition, and prenylation via radical-mediated pathways, with optimized conditions that only require the photocatalyst and a sacrificial reductant/hydrogen atom donor. Many of these reactions involve organobromide and organochloride substrates which in the past have had limited utility in photoredox catalysis. This work paves the way for the continued expansion of the substrate scope in photoredox catalysis.

Strong bis-cyclometalated iridium photoreductants, in combination with a single sacrificial reductant, enable visible-light-promoted reductive activation of a variety of challenging substrates under simple and general reaction conditions.     

General Enantioselective C−H Activation with Efficiently Tunable Cyclopentadienyl Ligands

Cyclopentadienyl (Cp) ligands enable efficient steering of various transition‐metal‐catalyzed transformations, in particular enantioselective C−H activation. Currently only few chiral Cp ligands are available. Therefore, a conceptually general approach to chiral Cp ligand discovery would be invaluable as it would enable the discovery of applicable Cp ligands and to efficiently and rapidly vary and tune their structures. Herein, we describe the three‐step gram‐scale synthesis of a structurally diverse and widely applicable chiral Cp ligand collection (JasCp ligands) with highly variable and adjustable structures. Their modular nature and their amenability to rapid structure variation enabled the efficient discovery of ligands for three enantioselective Rh^III‐catalyzed C−H activation reactions, including one unprecedented transformation. This novel approach should enable the discovery of efficient chiral Cp ligands for various further enantioselective transformations.     

High-Throughput Diversification of Complex Bioactive Molecules by Accelerated Synthesis in Microdroplets

Late-stage diversification of drug molecules is an important strategy in drug discovery that can be facilitated by reaction screening using high-throughput experimentation. Here we present a rapid method for functionalizing bioactive molecules based on accelerated reactions in microdroplets. Reaction mixtures are nebulized at throughputs better than 1 reaction/second and the accelerated reactions occurring in the microdroplets are followed by desorption electrospray ionization mass spectrometry (DESI-MS). Because the accelerated reactions occur on the millisecond timescale, they allow an overall screening throughput of 1 Hz working at the low nanogram scale. Using this approach, an opioid agonist (PZM21) and an antagonist (naloxone) were diversified using three reactions important in medicinal chemistry: sulfur fluoride exchange (SuFEx) click reactions, imine formation reactions, and ene-type click reactions. Some 269 functionalized analogs of naloxone and PZM21 were generated and characterized by tandem mass spectrometry (MS/MS) after screening over 500 reactions.     

Microfluidics for cell-based high throughput screening platforms—A review

In the last decades, the basic techniques of microfluidics for the study of cells such as cell culture, cell separation, and cell lysis, have been well developed. Based on cell handling techniques, microfluidics has been widely applied in the field of PCR (Polymerase Chain Reaction), immunoassays, organ-on-chip, stem cell research, and analysis and identification of circulating tumor cells. As a major step in drug discovery, high-throughput screening allows rapid analysis of thousands of chemical, biochemical, genetic or pharmacological tests in parallel. In this review, we summarize the application of microfluidics in cell-based high throughput screening. The screening methods mentioned in this paper include approaches using the perfusion flow mode, the droplet mode, and the microarray mode. We also discuss the future development of microfluidic based high throughput screening platform for drug discovery.     

Characterizing chain processes in visible light photoredox catalysis

The recognition that Ru(bpy)₃²⁺ and similar visible light absorbing transition metal complexes can be photocatalysts for a variety of synthetically useful organic reactions has resulted in a recent resurgence of interest in photoredox catalysis. However, many of the critical mechanistic aspects of this class of reactions remain poorly understood. In particular, the degree to which visible light photoredox reactions involve radical chain processes has been a point of some disagreement that has not been subjected to systematic analysis. We have now performed quantum yield measurements to demonstrate that three representative, mechanistically distinct photoredox processes involve product-forming chain reactions. Moreover, we show that the combination of quantum yield and luminescence quenching experiments provides a rapid method to estimate the length of these chains. Together, these measurements constitute a robust, operationally facile strategy for characterizing chain processes in a wide range of visible light photoredox reactions.     

Combinatorial synthesis in micro reactors

This article reviews the current and future applications of micro reactors in the field of combinatorial chemistry and drug discovery. Liquid phase reactions have been used to illustrate the advantages of performing chemical reactions in micro reactors which illustrate that reactions can be performed very rapidly in high yield to enable the preparation of combinatorial libraries of structurally related compounds.     

Advances in zebrafish high content and high throughput technologies

The zebrafish has emerged as an excellent transitional screening model system between cell-based assays, which are rapid and inexpensive but have limited physiological relevance, and higher vertebrate models, which have better physiological relevance, but are more time-consuming and expensive to deploy. As vertebrates, zebrafish maintain significant evolutionary proximity to humans and have been validated as robust models for drug research, studies of mechanism and behavioral genetics. Unlike higher vertebrate models, zebrafish are well-suited to high-throughput applications owing to their high fecundity, rapid extrauterine development and transparency during organogenesis enabling in vivo labeling and imaging. Recent advances have been made in automating high content and high-throughput zebrafish screens, with the goal of developing fully automated drug screening platforms. The application and continued development of these technologies holds potential clinical significance in drug discovery and elucidating disease mechanisms.     

Prediction of Human Drug Absorption Using Liposome Electrokinetic Chromatography

With the tremendously increasing numbers of novel drug candidates, there remains a compelling need for rapid screening methods for drug-like physiochemical and pharmacokinetic properties. Different technologies have emerged that enable rapid screening in vitro for sorting out new chemical entity (NCE) classes. It is invaluable for these technologies being developed early in the drug discovery process to avoid the loss of cost and time in late development due to poor absorption and/or bioavailability. In this study, liposome electrokinetic chromatography (LEKC) serves as a convenient, rapid and cost-effective tool to determine lipophilicity and to predict human oral absorption. Twenty-seven organic neutral molecules were evaluated by octanol/water system (log P _ow) and LEKC (log k), and linear solvation energy relationship (LSER) analysis was conducted to compare the retention mechanism between LEKC and octanol/water system. LEKC can provide a rapid indirect measurement of log P _ow for small organic neutral molecules. A clearly sigmoidal relationship could be seen by correlating log k with the fraction of 25 drugs absorbed in humans (Fa), and the outliers suggested the involvement of non-transcellular passive diffusion, e.g. active transport, paracellular route; on the contrary, it is not the case with the octanol/water system. Therefore, LEKC, in combination with other permeability prediction model, can provide a primary screen for a large number of drug candidates at early stage of the drug discovery process with high-throughput and at low-cost.     

A simpler sampling interface of venturi easy ambient sonic-spray ionization mass spectrometry for high-throughput screening enzyme inhibitors

High-throughput screening (HTS) is often required in enzyme inhibitor drugs screening. Mass spectrometry (MS) provides a powerful method for high-throughput screening enzyme inhibitors because its high speed, sensitivity and property of lable free. However, most of the MS methods need complicated sampling interface system. Overall throughput was limited by sample loading in these cases. In this study, we develop a simple interface which coupled droplet segmented system to a venturi easy ambient sonic-spray ionization mass spectrometer. It is fabricated by using a single capillary to act as both sampling probe and the emitter, which simplifies the construction, reduces the cost and shorten the sampling time. Samples sucked by venturi effect are segmented to nanoliter plugs by air, then the plugs can be detected by MS directly. This system eliminated the need for flow injection which was popular used in classic scheme. The new system is applied to screen angiotensin converting enzyme inhibitors. High-throughput was achieved in analyzing 96 samples at 1.6 s per sample. The plugs formation was at 0.5s per sample. Carry-over between samples was less than 5%, the peak height RSD was 2.92% (n = 15). Dose-response curves of 3 known inhibitors were also measured to validate its potential in drug discovery. The calculated IC₅₀ agreed well with reported values.     

Visible-light-mediated direct perfluoroalkylation and trifluoromethylation of free anilines

A mild, operationally simple method for direct perfluoroalkylation and trifluoromethylation of anilines through visible-light-mediated photoredox catalysis from broadly available perfluoroalkyl iodides and free anilines is described. The method provides a facile route for application in drug discovery and development.     

Multiple ligand detection and affinity measurement by ultrafiltration and mass spectrometry analysis applied to fragment mixture screening

Binding affinity of a small molecule drug candidate to a therapeutically relevant biomolecular target is regarded the first determinant of the candidate's efficacy. Although the ultrafiltration-LC/MS (UF-LC/MS) assay enables efficient ligand discovery for a specific target from a mixed pool of compounds, most previous analysis allowed for relative affinity ranking of different ligands. Moreover, the reliability of affinity measurement for multiple ligands with UF-LC/MS has hardly been strictly evaluated. In this study, we examined the accuracy of K_d determination through UF-LC/MS by comparison with classical ITC measurement. A single-point K_d calculation method was found to be suitable for affinity measurement of multiple ligands bound to the same target when binding competition is minimized. A second workflow based on analysis of the unbound fraction of compounds was then developed, which simplified sample preparation as well as warranted reliable ligand discovery. The new workflow implemented in a fragment mixture screen afforded rapid and sensitive detection of low-affinity ligands selectively bound to the RNA polymerase NS5B of hepatitis C virus. More importantly, ligand identification and affinity measurement for mixture-based fragment screens by UF-LC/MS were in good accordance with single ligand evaluation by conventional SPR analysis. This new approach is expected to become a valuable addition to the arsenal of high-throughput screening techniques for fragment-based drug discovery.