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Natural product chemistry

Robert A Hill, Andrew Sutherland
A personal selection of 32 recent papers is presented covering various aspects of current developments in bioorganic chemistry and novel natural products such as furanmonogone A from Hypericum monogynum.
March 21, 2017: Natural Product Reports
B Amato, S Petit
The knowledge of floral nectar sugar characteristics such as concentration, ratio, and mass is essential to understand the complex nature of nectar production and pollination systems. Although nectar is commonly stored in ecology, storage reliability and effectiveness have rarely been quantified. Inappropriate nectar storage between sampling and analysis can alter nectar chemistry as a result of enzyme or microbial action. Our review of the literature indicates that measures to preserve nectar sugars before analysis include refrigeration, freezing, the addition of an antimicrobial agent, spotting and drying on filter paper, the addition of a desiccant, or a combination of these storage treatments...
March 17, 2017: Plant Biology
Linee Goswami, Ki-Hyun Kim, Akash Deep, Pallabi Das, Satya Sundar Bhattacharya, Sandeep Kumar, Adedeji A Adelodun
Increased application of engineered nano particles (ENPs) in production of various appliances and consumer items is increasing their presence in the natural environment. Although a wide variety of nano particles (NPs) are ubiquitously dispersed in ecosystems, risk assessment guidelines to describe their ageing, direct exposure, and long-term accumulation characteristics are poorly developed. In this review, we describe what is known about the life cycle of ENPs and their impact on natural systems and examine if there is a cohesive relationship between their transformation processes and bio-accessibility in various food chains...
March 13, 2017: Journal of Environmental Management
Carin C C Johansson Seechurn, Theresa Sperger, Thomas G Scrase, Franziska Schoenebeck, Thomas J Colacot
The reduction of Pd(II) intermediates to Pd(0) is a key elementary step in a vast number of Pd-catalyzed processes, ranging from cross-coupling, C-H activation to Wacker chemistry. For one of the most powerful new generation phosphine ligands, PtBu3, oxidation state Pd(I), and not Pd(0), is generated upon reduction from Pd(II). The mechanism of the reduction of Pd(II) to Pd(I) has been investigated by means of experimental and computational studies for the formation of the highly active precatalyst [{Pd(μ-Br)(PtBu3)}2]...
March 16, 2017: Journal of the American Chemical Society
L René Corrales, Thomas D Yi, Samantha K Trumbo, David Shalloway, Jonathan I Lunine, David A Usher
The atmosphere of Titan, Saturn's largest moon, exhibits interesting UV- and radiation-driven chemistry between nitrogen and methane, resulting in dipolar, nitrile-containing molecules. The assembly and subsequent solvation of such molecules in the alkane lakes and seas found on the moon's surface are of particular interest for investigating the possibility of prebiotic chemistry in Titan's hydrophobic seas. Here we characterize the solvation of acetonitrile, a product of Titan's atmospheric radiation chemistry tentatively detected on Titan's surface [H...
March 14, 2017: Journal of Chemical Physics
Jadwiga Pyziak, Jędrzej Walkowiak, Bogdan Marciniec
In the syntheses developed to access naturally occurring compounds, especially bioactive substances, boron-functionalized dienes (also "linchpin" reagents) are used as key reagents. Structurally unique dienes are found in nature, and play important biological and chemical roles. Recently, linchpin moieties have been proved as useful substrates for a variety of highly functionalized chemical transformations. The products of these processes are potentially of some use for the syntheses of an important class of natural products showing a wide range of biological activities...
March 13, 2017: Chemistry: a European Journal
Lucie Nurdin, Denis M Spasyuk, Warren E Piers, Laurent Maron
Neutral cobalt(II) complexes of the dianionic tetrapodal pentadentate ligand B2Pz4Py, in which borate linkers supply the anionic charges, are reported. Both the six-coordinate THF adduct 1-THF and the five-coordinate THF-free complex 1 are in a high-spin S = 3/2 configuration in the ground state and have been structurally characterized by X-ray crystallography. These two Co(II) starting materials react rapidly with aryl azides of moderate steric bulk. The thermodynamic products of these reactions are low-spin, diamagnetic, Co(III) amido complexes that are either monomeric, when an external hydrogen atom source such as 1,4-cyclohexadiene is present, or dimeric products formed via C-C coupling of the azide aryl group and internal transfer of H(•) to the nitrogen...
March 15, 2017: Inorganic Chemistry
Mirko Paulikat, Cindy Wechsler, Kai Tittmann, Ricardo A Mata
Electronic absorption spectra are often times used to identify reaction intermediates or substrates/products in enzymatic systems, as long as absorption bands can be unequivocally assigned to the species under study. The latter task is far from trivial given the transient nature of some states and the complexity of the surrounding environment around the active site. In order to identify unique spectral fingerprints, controlled experiments on model compounds have been used in the past, but even these can sometimes be unreliable...
March 15, 2017: Biochemistry
Ivan Zemskov, Stefan Altaner, Daniel R Dietrich, Valentin Wittmann
Microcystins (MCs) are highly toxic natural products which are produced by cyanobacteria. They can be released to the water during harmful algal blooms and are a serious threat to animals and humans. Described is the total synthesis of the cyanotoxin microcystin-LF (MC-LF, 1a) and two derivatives thereof. Deuterated derivative 1b is of interest as an internal standard during MC quantification in biological samples by mass spectrometry and alkyne-labeled 1c can be employed for toxin derivatization by click chemistry with an azide-containing reporter molecule or as an activity-based probe to identify interaction partners...
March 15, 2017: Journal of Organic Chemistry
Zachary G Brill, Matthew L Condakes, Chi P Ting, Thomas J Maimone
The pool of abundant chiral terpene building blocks (i.e., "chiral pool terpenes") has long served as a starting point for the chemical synthesis of complex natural products, including many terpenes themselves. As inexpensive and versatile starting materials, such compounds continue to influence modern synthetic chemistry. This review highlights 21st century terpene total syntheses which themselves use small, terpene-derived materials as building blocks. An outlook to the future of research in this area is highlighted as well...
March 15, 2017: Chemical Reviews
Koffi Sénam Etsè, Alice Ngendera, Nelly Tshibalonza Ntumba, Albert Demonceau, Lionel Delaude, Ileana Dragutan, Valerian Dragutan
Over the last two decades, olefin metathesis has emerged as a new avenue in the design of new routes for the synthesis of natural products and active pharmaceutical ingredients. In many cases, syntheses based on olefin metathesis strategies provide elegant routes in terms of increasing the overall yields, improving the synthesis scope, and decreasing the number of steps. On the other hand, over the last decade, microwave-assisted chemistry has experienced an incredible development, which rapidly opened new vistas in organic synthesis and in homogeneous catalysis...
March 14, 2017: Current Medicinal Chemistry
Samantha L Kristufek, Kevin T Wacker, Yi-Yun Timothy Tsao, Lu Su, Karen L Wooley
Covering: 2010-Aug. 2016In an effort towards enhancing function and sustainability, natural products have become of interest in the field of polymer chemistry. This review details the blending of chemistries developed through synthetic organic chemistry and polymer chemistry. Through synthetic organic chemical transformations, such as functional group interconversion, a protection/deprotection series, or installation of a functional group, various designs towards novel, synthetic, bio-based polymer systems are described...
March 14, 2017: Natural Product Reports
Rachelle Quach, Daniel P Furkert, Margaret A Brimble
In the last decade the use of homogenous gold catalysts has rapidly grown and become a valuable tool for complex natural product synthesis. Spiroketal natural products are valuable targets for total synthesis and medicinal chemistry applications. The use of gold catalysts has emerged as a useful tool to synthesise these privileged scaffolds. This review summarises the application of gold catalysis for the syntheses of spiro, bridged and fused ketal natural products.
March 13, 2017: Organic & Biomolecular Chemistry
Simon Companys, Laurent Pouységu, Philippe A Peixoto, Stefan Chassaing, Stephane Quideau
Two model ortho-quinol acetates were easily prepared by iodane-mediated acetoxylative phenol dearomatization and evaluated for their reactivity towards various aryl-based nucleophiles, i.e., aryl metallic reagents and phenolic derivatives. Novel modes of reactivity, allowing the formation of biaryl linkages, were revealed and here exploited for the synthesis of two natural phenolics.
March 10, 2017: Journal of Organic Chemistry
Steven J Rowland, Paul A Sutton
We describe determination of the dichloromethane-soluble components of 12 samples of the natural product, ambergris, using capillary gas chromatography-mass spectrometry (GC-MS). Ambergris is produced in vivo in about 1% of Sperm whales and is used in perfumery and for odour fixation. Whilst descriptions of ambergris chemistry appeared until about 40 years ago, few accounts of analyses of whole extracts of multiple samples of ambergris by GC-MS have been published before. As expected, our analyses revealed that the major component (up to 97% of the dichloromethane-soluble material) was ambrein, with co-occurring, variable proportions of steroids...
February 16, 2017: Natural Product Research
Ramzi Khiari, Marie-Christine Brochier Salon, Mohamed Farouk Mhenni, Evelyne Mauret, Mohamed Naceur Belgacem
The development of new derivatives based on renewable natural resources using green chemistry is a concept gaining recognition in several industries. This work focused on the preparation and characterization of cellulose carbonate using dimethyl carbonate as the green reagent in ethanoic KOH solution. The effect of several reaction parameters were evaluated, i.e., temperature (25°C, 50°C, 90°C, 120°C, 150°C, and 180°C), time (6, 24, 48, and 72h), KOH concentration (15% and 30%), and the use of a catalyst (DBU)...
May 1, 2017: Carbohydrate Polymers
Liang-An Chen, Melissa A Ashley, James L Leighton
Because of both their synthetically challenging and stereochemically complex structures and their wide range of often clinically relevant biological activities, nonaromatic polyketide natural products have for decades attracted an enormous amount of attention from synthetic chemists and played an important role in the development of modern asymmetric synthesis. Often, such compounds are not available in quantity from natural sources, rendering analogue synthesis and drug development efforts extremely resource-intensive and time-consuming...
March 15, 2017: Journal of the American Chemical Society
Karsten Korschelt, Ruben Ragg, Carmen S Metzger, Martin Kluenker, Michael Oster, Bastian Barton, Martin Panthöfer, Dennis Strand, Ute Kolb, Mihail Mondeshki, Susanne Strand, Jürgen Brieger, M Nawaz Tahir, Wolfgang Tremel
Superoxide dismutases (SOD) are a group of enzymes that catalyze the dismutation of superoxide (O2(-)) radicals into molecular oxygen (O2) and H2O2 as a first line of defense against oxidative stress. Here, we show that glycine-functionalized copper(ii) hydroxide nanoparticles (Gly-Cu(OH)2 NPs) are functional SOD mimics, whereas bulk Cu(OH)2 is insoluble in water and catalytically inactive. In contrast, Gly-Cu(OH)2 NPs form water-dispersible mesocrystals with a SOD-like activity that is larger than that of their natural CuZn enzyme counterpart...
March 7, 2017: Nanoscale
Zuly Elizabeth Jiménez Pérez, Ramya Mathiyalagan, Josua Markus, Yeon-Ju Kim, Hyun Mi Kang, Ragavendran Abbai, Kwang Hoon Seo, Dandan Wang, Veronika Soshnikova, Deok Chun Yang
There has been a growing interest in the design of environmentally affable and biocompatible nanoparticles among scientists to find novel and safe biomaterials. Panax ginseng Meyer berries have unique phytochemical profile and exhibit beneficial pharmacological activities such as antihyperglycemic, antiobesity, antiaging, and antioxidant properties. A comprehensive study of the biologically active compounds in ginseng berry extract (GBE) and the ability of ginseng berry (GB) as novel material for the biosynthesis of gold nanoparticles (GBAuNPs) and silver nanoparticles (GBAgNPs) was conducted...
2017: International Journal of Nanomedicine
Brandon J Burkhart, Christopher J Schwalen, Greg Mann, James H Naismith, Douglas A Mitchell
With advances in sequencing technology, uncharacterized proteins and domains of unknown function (DUFs) are rapidly accumulating in sequence databases and offer an opportunity to discover new protein chemistry and reaction mechanisms. The focus of this review, the formerly enigmatic YcaO superfamily (DUF181), has been found to catalyze a unique phosphorylation of a ribosomal peptide backbone amide upon attack by different nucleophiles. Established nucleophiles are the side chains of Cys, Ser, and Thr which gives rise to azoline/azole biosynthesis in ribosomally synthesized and posttranslationally modified peptide (RiPP) natural products...
March 3, 2017: Chemical Reviews
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