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Natural product chemistry

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https://www.readbyqxmd.com/read/29665280/chemistry-of-cyanide-adducts-of-aldimines-from-aniline-derivatives
#1
REVIEW
Eunjoon Park, Jiye Jeon, Cheol-Hong Cheon
The chemistry of hydrogen cyanide adducts of imines is well-developed, but that of cyanide adducts remains unexplored. This is presumably because these cyanide adducts are not stable and thus not readily available in their isolated forms. In this personal account, we present the progress made in our research program towards the development of novel organic transformations utilizing cyanide adducts of imines as key intermediates. We also report the application of these methodologies to the total synthesis of natural products including indole alkaloids...
April 17, 2018: Chemical Record: An Official Publication of the Chemical Society of Japan ... [et Al.]
https://www.readbyqxmd.com/read/29664412/superconducting-selenides-intercalated-with-organic-molecules-synthesis-crystal-structure-electric-and-magnetic-properties-superconducting-properties-and-phase-separation-in-iron-based-chalcogenides-and-hybrid-organic-inorganic-superconductors
#2
Anna Krzton-Maziopa, Edyta Pesko, Roman Puzniak
Layered iron-based superconducting chalcogenides intercalated with molecular species are the subject of intensive studies, especially in the field of solid state chemistry and condensed matter physics, because of their intriguing chemistry and tunable electric and magnetic properties. Considerable progress in the research, revealing superconducting inorganic organic hybrid materials with transition temperatures to superconducting state, Tc, up to 46 K, has been brought in recent years. These novel materials are synthesized by low temperature intercalation of molecular species, such as solvates of alkali metals and nitrogen-containing donor compounds, into layered FeSe-type structure...
April 17, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/29664305/copper-catalyzed-oxygenation-approach-to-oxazoles-from-amines-alkynes-and-molecular-oxygen
#3
Jun Pan, Xinyao Li, Xu Qiu, Xiao Luo, Ning Jiao
A novel and efficient oxygenation approach to trisubstituted oxazoles via a copper-catalyzed aerobic oxidative dehydrogenative annulation of amines, alkynes, and O2 has been developed. This transformation combines dioxygen activation and oxidative C-H bond functionalization and provides a practical protocol for the preparation of oxazole derivatives, which are privileged units found in various bioactive compounds or other natural products. 18 O-labeling experiments were conducted to reveal that oxygenation was involved in this chemistry...
April 17, 2018: Organic Letters
https://www.readbyqxmd.com/read/29663810/dual-catalytic-synthesis-of-antiviral-compounds-based-on-metallocarbene-azide-cascade-chemistry
#4
Bren Jordan P Atienza, Lionel Dylan Jensen, Sarah L Noton, Anil Kumar Victoria Ansalem, Tom Hobman, Rachel Fearns, David J Marchant, F G West
Aryl azides trap ortho metallocarbene intermediates to generate indolenones possessing a reactive C-acylimine moiety, which can react with added indole nucleophiles to afford the 2-(3-indolyl)indolin-3-one scaffold found in the antiviral natural product isatisine A. This overall process occurs through a dual catalytic sequence at room temperature. Redox activation of the Cu(OTf)2 precatalyst by indole results in catalytically competent Cu(I) required for azide-metallocarbene coupling. The Brønsted acid that is also formed from Cu(OTf)2 reduction is responsible for catalysis of the C-C bond-forming indole addition step...
April 17, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29662986/discovery-and-characterization-of-natural-products-that-act-as-pheromones-in-fish
#5
REVIEW
Ke Li, Tyler J Buchinger, Weiming Li
Covering: up to 2018Fish use a diverse collection of molecules to communicate with conspecifics. Since Karlson and Lüscher termed these molecules 'pheromones', chemists and biologists have joined efforts to characterize their structures and functions. In particular, the understanding of insect pheromones developed at a rapid pace, set, in part, by the use of bioassay-guided fractionation and natural product chemistry. Research on vertebrate pheromones, however, has progressed more slowly. Initially, biologists characterized fish pheromones by screening commercially available compounds suspected to act as pheromones based upon their physiological function...
April 17, 2018: Natural Product Reports
https://www.readbyqxmd.com/read/29656544/an-overview-on-the-identification-of-mait-cell-antigens
#6
Lars Kjer-Nielsen, Alexandra J Corbett, Zhenjun Chen, Ligong Liu, Jeffrey Y W Mak, Dale I Godfrey, Jamie Rossjohn, David P Fairlie, James McCluskey, Sidonia B G Eckle
Mucosal Associated Invariant T (MAIT) cells are restricted by the monomorphic MHC class I-like molecule, MHC-related protein-1 (MR1). Until 2012, the origin of the MAIT cell antigens (Ags) was unknown, although it was established that MAIT cells could be activated by a broad range of bacteria and yeasts, possibly suggesting a conserved Ag. Using a combination of protein chemistry, mass spectrometry, cellular biology, structural biology and chemistry, we discovered MAIT cell ligands derived from folic acid (vitamin B9) and from an intermediate in the microbial biosynthesis of riboflavin (vitamin B2)...
April 14, 2018: Immunology and Cell Biology
https://www.readbyqxmd.com/read/29649566/spatio-temporal-monitoring-of-lipid-peroxyl-radicals-in-live-cell-studies-combining-fluorogenic-antioxidants-and-fluorescence-microscopy-methods
#7
REVIEW
Lana E Greene, Richard Lincoln, Gonzalo Cosa
Lipid peroxidation of polyunsaturated fatty acids in cells may occur via their catalytic autoxidation through peroxyl radicals under oxidative stress conditions. Lipid peroxidation is related to a number of pathologies, and may be invoked in new forms of regulated cell death, yet it may also have beneficial roles in cell signaling cascades. Antioxidants are a natural line of defense against lipid peroxidation, and may accordingly impact the biological outcome associated with the redox chemistry of lipid peroxidation...
April 9, 2018: Free Radical Biology & Medicine
https://www.readbyqxmd.com/read/29648789/copper-catalyzed-oxidative-carbon-carbon-and-or-carbon-heteroatom-bond-formation-with-o-2-or-internal-oxidants
#8
Xiaodong Tang, Wanqing Wu, Wei Zeng, Huanfeng Jiang
Selective oxidation, a fundamental organic transformation of critical importance, produces value-added products from simple organic molecules. This process is extensively used to incorporate heteroatoms into carbon-based molecules, where high-valent metal salts, hypervalent halogen reagents, and peroxides are widely used as oxidants. Oxidation reactions are extremely challenging because their selectivity is hard to control and/or they form significant quantities of unwanted waste derived from the stoichiometric oxidants...
April 12, 2018: Accounts of Chemical Research
https://www.readbyqxmd.com/read/29645063/realisation-of-small-molecule-libraries-based-on-frameworks-distantly-related-to-natural-products
#9
Anthony Aimon, George Karageorgis, Jacob Masters, Mark Dow, Philip G E Craven, Martin Ohsten, Anthony Willaume, Rémy Morgentin, Nicolas Ruiz-Llamas, Hugues Lemoine, Tuomo Kalliokoski, Andrew J Eatherton, Daniel J Foley, Stephen P Marsden, Adam Nelson
The availability of high-quality screening compounds is of paramount importance for the discovery of innovative new medicines. Natural product (NP) frameworks can inspire the design of productive compound libraries. Here, we describe the design and synthesis of four compound libraries based on scaffolds that have broad NP-like features, but that are only distantly related to specific NPs. The optimisation of syntheses of the scaffolds using [5 + 2] cycloaddition chemistry is detailed, together with methods to yield exemplar decorated screening compounds...
April 12, 2018: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/29644551/lipase-catalyzed-epoxidation-of-fatty-acid-methyl-esters-derived-from-unsaturated-vegetable-oils-in-absence-of-carboxylic-acid
#10
Alejandro Sustaita-Rodríguez, Víctor H Ramos-Sánchez, Alejandro A Camacho-Dávila, Gerardo Zaragoza-Galán, José C Espinoza-Hicks, David Chávez-Flores
Nowadays the industrial chemistry reactions rely on green technologies. Enzymes as lipases are increasing its use in diverse chemical processes. Epoxidized fatty acid methyl esters obtained from transesterification of vegetable oils have recently found applications as polymer plasticizer, agrochemical, cosmetics, pharmaceuticals and food additives. In this research article, grapeseed, avocado and olive oils naturally containing high percents of mono and poly unsaturations were used as starting materials for the production of unsaturated fatty acid methyl esters...
April 11, 2018: Chemistry Central Journal
https://www.readbyqxmd.com/read/29629768/mechanistic-study-on-cu-ii-catalyzed-oxidative-cross-coupling-reaction-between-arenes-and-boronic-acids-under-aerobic-conditions
#11
Qian Zhang, Yang Liu, Ting Wang, Xinhao Zhang, Chao Long, Yun-Dong Wu, Mei-Xiang Wang
Substantial attention has been given to modern organocopper chemistry in recent years because of the need of sustainabil-ity since copper salts are naturally abundant, cheap and less-toxic in comparison to precious metals. Copper salts also ex-hibit versatility in catalyzing and mediating carbon-carbon and carbon-heteroatom bond forming reactions. Despite the wide applications of copper salts in catalysis, reaction mechanisms have remained elusive. Using azaca-lix[1]arene[3]pyridine, an arene-embedded macrocycle, and its isolated and structurally well-defined ArCu(II) and ArCu(III) compounds as molecular tools, we now report an in-depth experimental and computational study on the mechanism of Cu(II)-catalyzed oxidative cross-coupling reaction between arenes and boronic acids with air as the oxidant...
April 9, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/29629070/a-lesson-for-site-selective-c-h-functionalization-on-2-pyridones-radical-organometallic-directing-group-and-steric-controls
#12
REVIEW
Koji Hirano, Masahiro Miura
A 2-pyridone ring is a frequently occurring subunit in natural products, biologically active compounds, and pharmaceutical targets. Thus, the selective synthesis of substituted 2-pyridone derivatives through decoration and/or formation of pyridone rings has been one of the important longstanding subjects in organic synthetic chemistry. This minireview focuses on recent advances in site-selective C-H functionalization on 2-pyridone. The reported procedures are categorized according to the site selectivity that is achieved, and the substrate scope, limitations, mechanism, and controlling factors are briefly summarized...
January 7, 2018: Chemical Science
https://www.readbyqxmd.com/read/29627458/synthetic-fermentation-of-bioactive-molecules
#13
REVIEW
Iain A Stepek, Jeffrey W Bode
The concept of synthetic fermentation is to 'grow' complex organic molecules in a controlled and predictable manner by combining small molecule building blocks in water-without the need for reagents, enzymes, or organisms. This approach mimics the production of small mixtures of structurally related natural products by living organisms, particularly microbes, under conditions compatible with direct screening of the cultures for biological activity. This review discusses the development and implementation of this concept, its use for the discovery of protease inhibitors, its basis as a chemistry outreach program allowing non-specialists to make and discover new antibiotics, and highlights of related approaches...
April 5, 2018: Current Opinion in Chemical Biology
https://www.readbyqxmd.com/read/29625876/recycling-of-polyurethanes-from-laboratory-to-industry-a-journey-towards-the-sustainability
#14
REVIEW
D Simón, A M Borreguero, A de Lucas, J F Rodríguez
The recycling of any kind of plastic to convert it in valuable products is one of the main challenges of today's society. Besides, if the recycling process is itself green, then it would be a great achievement. This paper reviews the way covered from the first attempts of reusing the polyurethane (PU) scraps as a filler for cushions to the last chemical routes employing green recycling agents. Polyurethane is the 6th most used polymer all over the world with a production of 18 millions tons per year, which means a daily production of PU specialties greater than 1 million of cubic meters, equivalent to the volume of the Empire State Building...
April 3, 2018: Waste Management
https://www.readbyqxmd.com/read/29624844/a-vastly-increased-chemical-variety-of-rna-modifications-that-includes-a-thioacetal-structure
#15
Christina Dal Magro, Patrick Keller, Annika Kotter, Stephan Werner, Victor Duarte, Virginie Marchand, Michael Ignarski, Anja Freiwald, Roman-Ulrich Müller, Christoph Dieterich, Yuri Motorin, Falk Butter, Mohammed Atta, Mark Helm
Recently discovered new chemical entities in RNA modifications have provided surprises with respect to functional groups that enlarge the chemical space of RNA. Using LC-MS, we found over one hundred signals of RNA constituents that contained a ribose moiety in tRNAs from E. coli. Feeding experiments with variegated stable isotope labeled compounds identified 37 compounds, representing new structures of RNA modifications. One structure was elucidated by deuterium exchange and high resolution mass spectrometry...
April 6, 2018: Angewandte Chemie
https://www.readbyqxmd.com/read/29623517/mini-review-on-photosensitization-by-plants-in-grazing-herbivores
#16
REVIEW
Syeda M Hussain, Valdo Rodrigues Herling, Paulo Henrique Mazza Rodrigues, Ishrat Naz, Hamayun Khan, Muhammad Tahir Khan
Photosensitization is severe dermatitis or oxidative/chemical changes in the epidermal tissues activated by the light-induced excitation of molecules within the tissue. It is a series of reactions mediated through light receptors and is more common when the plant-produced metabolites are heterocyclic/polyphenols in nature. The areas affected are exposed body parts and mostly non-pigmented areas with least ultraviolet protection. Similarly, cellular alteration also occurs in the affected animal's dermal tissues and body parts and grazing animals by the accumulation and activation of photodynamic molecules...
April 6, 2018: Tropical Animal Health and Production
https://www.readbyqxmd.com/read/29620883/an-oxetane-based-polyketide-surrogate-to-probe-substrate-binding-in-a-polyketide-synthase
#17
Bryan Daniel Ellis, Jacob C Milligan, Alexander R White, Vy Duong, Pilar X Altman, Lina Mohammed, Matthew P Crump, John Crosby, Ray Luo, Christopher D Vanderwal, Shiou-Chuan Tsai
Polyketides are a large class of bioactive natural products with a wide range of structures and functions. Polyketides are biosynthesized by large, multi-domain enzyme complexes termed polyketide synthases (PKSs). One of the primary challenges when studying PKSs is the high reactivity of their poly--ketone substrates. This has hampered structural and mechanistic characterization of PKS-polyketide complexes, and, as a result, little is known about how PKSs position the unstable substrates for proper catalysis while displaying high levels of regio- and stereo-specificity...
April 5, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/29616689/kinetics-in-the-real-world-linking-molecules-processes-and-systems
#18
EDITORIAL
Katharina Kohse-Höinghaus, Jürgen Troe, Jens-Uwe Grabow, Matthias Olzmann, Gernot Friedrichs, Klaus-Dieter Hungenberg
Unravelling elementary steps, reaction pathways, and kinetic mechanisms is key to understanding the behaviour of many real-world chemical systems that span from the troposphere or even interstellar media to engines and process reactors. Recent work in chemical kinetics provides detailed information on the reactive changes occurring in chemical systems, often on the atomic or molecular scale. The optimisation of practical processes, for instance in combustion, catalysis, battery technology, polymerisation, and nanoparticle production, can profit from a sound knowledge of the underlying fundamental chemical kinetics...
April 4, 2018: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/29614406/bivalve-shell-formation-in-a-naturally-co-2-enriched-habitat-unraveling-the-resilience-mechanisms-from-elemental-signatures
#19
Liqiang Zhao, Stefania Milano, Eric O Walliser, Bernd R Schöne
Marine bivalves inhabiting naturally pCO2 -enriched habitats can likely tolerate high levels of acidification. Consequently, elucidating the mechanisms behind such resilience can help to predict the fate of this economically and ecologically important group under near-future scenarios of CO2 -driven ocean acidification. Here, we assess the effects of four environmentally realistic pCO2 levels (900, 1500, 2900 and 6600 μatm) on the shell production rate of Mya arenaria juveniles originating from a periodically pCO2 -enriched habitat (Kiel Fjord, Western Baltic Sea)...
March 28, 2018: Chemosphere
https://www.readbyqxmd.com/read/29611478/virtual-screening-studies-for-discovery-of-novel-inhibitors-of-inflammatory-process-targets
#20
Marcus Tullius Scotti, Mateus Feitosa Alves, Chonny Alexander Herrera-Acevedo, Luciana Scotti
Inflammation has been very evident in infectious diseases, but in recent times research has increasingly shown that a range of non-infectious diseases may present with inflammatory conditions. This fact becomes important as new anti-inflammatory drugs emerge with different targets for treatment of diseases. Virtual screening (VS) involves applying computational methods to discover new ligands for biological structures from the formation of large libraries composed of a large number of compounds. This review aims to report several studies employing a variety of VS: ligand-based and structure-based VS are being used more frequently in combination to decrease the probability of choosing false positive candidates...
April 3, 2018: Current Pharmaceutical Design
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