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Jinping Gu, Chenyang Ji, Siqing Yue, Dan Shu, Feng Su, Yinjun Zhang, Yuanyuan Xie, Yi Zhang, Weiping Liu, Meirong Zhao
More than 30% of the registered pesticides are chiral with one or more chiral centers and exist as two or more enantiomers. The frequency of chiral chemicals and their environmental safety has been considered in their risk assessment in recent decades. Despite the fact that metabolic disturbance is an important sensitive molecular initiating event of toxicology effects, the potential mechanisms of how chiral compounds affect metabolism phenotypes in organisms remain unclear. As a typical chiral pesticide, metalaxyl is an acylalanine fungicide with systemic function...
April 23, 2018: Environmental Science & Technology
Chao Che, Zhaosheng Qian, Mingchang Wu, Ying Zhao, Gangguo Zhu
A novel silver-catalyzed ring-opening acylation of cyclopropanols and cyclobutanols is described. The reaction proceeds under mild and neutral conditions and provides a facile access to nonsymmetric 1,4- and 1,5-diketones in promising yields with broad substrate scope. Mechanistic studies including DFT calculations suggest the involvement of an uncommon water-assisted 1,2-HAT process, which is strongly exothermic and thus promotes addition of carbon radicals to aldehydes. In contrast to traditional reductive radical addition protocols, this work represents the first example on the intermolecular oxidative radical addition to aldehydes, thus offering a novel strategy for the direct synthesis of acyclic ketones from readily accessible aldehydes...
April 23, 2018: Journal of Organic Chemistry
Mohd Waheed, Naseem Ahmed, Meshari A Alsharif, Mohammed Issa Alahmdi, Sayeed Mukhtar
A facile synthesis of 1,5-diketones from 3-acetyl-4-hydroxycoumarin, aldehydes and cyclic-ketones via a one-pot aldol condensation and subsequent Michael addition reaction in the presence of a single catalyst of l-proline under mild reaction conditions has been developed. Novel 1,5-diketones were further cyclized to unexpected 3,4-dihydropyridines rather than generally formed pyridine analogues with ammonium acetate in acetic acid. One pot, high yields (72-92%) for novel 1,5-diketones and (70-90%) for the 3,4-dihydropyridine adducts, easy work-up and purification of products are the key advantages of this method...
April 23, 2018: Organic & Biomolecular Chemistry
Timothy B Boit, Nicholas A Weires, Junyong Kim, Neil K Garg
We report the Ni-catalyzed Suzuki-Miyaura coupling of aliphatic amide derivatives. Prior studies have shown that aliphatic amide derivatives can undergo Ni-catalyzed carbon-heteroatom bond formation but that Ni-mediated C-C bond formation using aliphatic amide derivatives has remained difficult. The coupling disclosed herein is tolerant of considerable variation with respect to both the amide-based substrate and the boronate coupling partner and proceeds in the presence of heterocycles and epimerizable stereocenters...
February 2, 2018: ACS Catalysis
Mohammad Paknahad, Jannat Singh Bachhal, Mina Hoorfar
This paper presents a cost-effective and reliable diffusion-based humidity removal membrane for microfluidic-based gas analyzers. The developed humidity control device reduces the relative humidity of a gas chamber and also stabilizes the humidity using inexpensive inorganic salts. A 3D-printed microfluidic gas sensor is used to test four different volatile organic compounds (VOCs) including three alcohols and one ketone in different relative humidity levels ranging from 15% to 80%. To study the effects of humidity on different features of the transient response of the sensor, two different feature extraction methods are used...
August 27, 2018: Analytica Chimica Acta
Wei Zhou, Chenlu Wang, Xuemei Wang, Zilin Chen
Development of stir bar sorptive extraction (SBSE) device with high stability and extraction efficiency is critical and challenging by date. In this work, etched poly(ether ether ketone) (PEEK) tube with high mechanical strength and large specific surface area was used as jacket for SBSE device. By etching with concentrated sulfuric acid, the smooth outer surface of PEEK become porous with plenty of micro holes, which was beneficial for coating of sorbents and significantly improved the extraction performance...
April 12, 2018: Journal of Chromatography. A
Jin Qian, Kun Li, Peifang Wang, Chao Wang, Jingjing Liu, Xin Tian, Bianhe Lu, Wenyi Guan
Engineered nano-TiO2 (Enano-TiO2 ) have inevitably discharged into aquatic sediments that resulted from their widespread use. The physicochemical characteristics of sediments might be changed because of remarkable properties of Enano-TiO2 and affected by the aging of sediments, thereby altering the environmental behavior and bioavailability of other pollutants such as perfluorooctane sulfonate (PFOS) in sediments. Here, adsorption behavior and mechanism of PFOS on aging aquatic sediments spiked with Enano-TiO2 at a weight ratio of 5...
April 20, 2018: Environmental Science and Pollution Research International
Kaitlyn Dahlgren, Kelly J Gibas
Alzheimer's disease (AD) deaths have increased by 89% since 2000. This alarming trajectory of neurological disease highlights the failure of current best practice. Deteriorating brain fuel supply is the nemesis of intact neurological health. Cerebral hypo-metabolism associated with AD occurs years before onset. Both the ketogenic diet and calorie restriction (fasting) lead to a compensatory rise in ketones to improve energy deficits in the brain derived from cerebral insulin resistance. Two forms of ketone bodies, β-hydroxybutyrate and acetoacetate, fuel the brain during starvation, fasting and strenuous exercise...
April 11, 2018: Diabetes & Metabolic Syndrome
Byeol-Nim Lee, Tae Yang Son, Chi Hoon Park, Tae Hyun Kim, Sang Yong Nam
In this study, various poly(ether ether ketone) were synthesized using three different monomers and the imidazolium group was introduced into synthesized poly(ether ether ketone)s by using substitution reaction. Synthesized polymers were used to prepare anion exchange membranes and to evaluate its properties. Thermal, chemical and structural properties were carried out using thermogravimetric analysis, nuclear magnetic resonance. The anion exchange membranes with different imidazolium moieties were characterized by several different analytical techniques such as water up take, ion exchange capacity, hydroxide conductivity for checking the possibility to apply the anion exchange membrane fuel cell...
September 1, 2018: Journal of Nanoscience and Nanotechnology
Young-Min Kim, Gwang Hoon Rhee, Chang Hyun Ko, Ki Hoon Kim, Kyeong Youl Jung, Ji Man Kim, Young-Kwon Park
The thermal and catalytic pyrolysis of Pinus densiflora (P. densiflora) were performed to test the catalytic cracking efficiency of two mesoporous Al2O3 catalysts with different surface areas. Thermogravimetric analysis (TGA) of P. densiflora showed that the differential TG (DTG) peak heights obtained from catalytic pyrolysis were smaller than those of non-catalytic pyrolysis due to the conversion of the reaction intermediates to coke. Pyrolyzer-gas chromatography/mass spectrometry analysis/flame ionization detection (Py-GC/MS/FID) suggested that using the Al2O3 catalysts, the yields of phenols and levoglucosan decreased with a concomitant increase in the yields of aldehydes, alcohol, ketones, and furans...
September 1, 2018: Journal of Nanoscience and Nanotechnology
Mabrouk Attia Abd Eldaim, Fatma Mohamed Ibrahim, Sahar H Orabi, Azza Hassan Morsi, Hesham Saad ElSabbagh
In this study the possible mechanisms through which L-carnitine ameliorates the adverse effects of high fat diet (HFD) induced obesity on rats was evaluated. 56 Wister albino rats were randomly assigned into seven groups. Control rats fed basal diet. 2nd group fed basal diet and injected with L-carnitine 200 mg/kg i.p. 3rd group fed HFD. 4th group fed HFD and injected with L-Carnitine 200 mg/kg i.p for 8 weeks. 5th group fed HFD for 10 weeks. 6th group fed HFD for 10 weeks and injected with L-Carnitine 200 mg/kg i...
April 20, 2018: Biochemistry and Cell Biology, Biochimie et Biologie Cellulaire
Xinxin Zheng, Rui Guo, Guozhu Zhang, Dayong Zhang
We report a rhodium-catalyzed asymmetric formal intermolecular [4 + 2] cycloaddition reaction of 2-alkylenecyclobutanols with α,β-unsaturated cyclic ketones leading to synthetically useful trans -bicyclic molecules. Three consecutive stereogenic centers are formed in a highly enantio- and diastereoselective manner. Stepwise C-C bond cleavage and annulation are likely involved in the reaction pathway. Here, iPr-Duphos is the viable chiral ligand that promotes excellent enantio-control.
February 21, 2018: Chemical Science
Lizeth Perez, Bethany G Caulkins, Magi Mettry, Leonard J Mueller, Richard J Hooley
The effects on the molecular recognition properties of water-soluble deep cavitand hosts upon embedding them in phosphocholine lipid bilayer environments have been studied by 2D NMR experiments. By employing suitable guests containing 19 F or 13 C nuclei that can be encapsulated inside the host, 2D EXSY NMR experiments can be used to analyze and compare the in/out guest exchange rates in aqueous solution, isotropically tumbling micelles, or magnetically ordered bicelles. These analyses show that embedding the deep cavitands in lipid bilayers slows the guest exchange rate, due to the lipids acting as a "compression sleeve" around the host, restricting guest egress...
February 21, 2018: Chemical Science
Xuehui Wang, Li Zhang, Jing Jin, Anting Xia, Chunmei Wang, Yingjun Cui, Bo Qu, Qingzhang Li, Chunyan Sheng
miRNAs play an important role in the processes of cell differentiation, biological development, and physiology. Here we investigated the molecular mechanisms regulating milk secretion and quality in dairy cows via transcriptome analyses of mammary gland tissues from dairy cows during the high-protein/high-fat, low-protein/low-fat or dry periods. To characterize the important roles of miRNAs and mRNAs in milk quality and to elucidate their regulatory networks in relation to milk secretion and quality, an integrated analysis was performed...
April 19, 2018: Scientific Reports
Wen-Fei Hu, Jian-Qiang Zhao, Yong-Zheng Chen, Xiao-Mei Zhang, Xiao-Ying Xu, Wei-Cheng Yuan
An efficient organocatalyzed enantioselective conjugated addition of sodium bisulfite to β-trifluoromethyl-α,β-unsaturated ketones using a cinchona alkaloid-derived squaramide catalyst is presented. A series of optically active sulfonic acids, bearing a tertiary stereocenter connecting a CF3 group and a SO3H group, were obtained in excellent yields with high enantioselectivities (up to 99% yield and 97% ee) under mild conditions. This method will provide an efficient, economic, and green route to access chiral sulfonic acid compounds...
April 19, 2018: Journal of Organic Chemistry
Dattatraya H Dethe, Samarpita Mahapatra, Susanta Kumar Sau
The first enantioselective total synthesis of (+)-taondiol, a pentacyclic marine meroterpenoid, has been achieved, which in addition to confirming the structure also established the absolute configuration of the natural product. The notable points in the synthetic route are synthesis of a highly functionalized tricyclic diterpenoid moiety starting from an enantiopure Wieland-Miescher ketone derivative in concise manner via Robinson-type annulation and an elegant hydrogen atom transfer olefin reduction followed by Lewis acid-catalyzed Friedel-Crafts reaction for one-pot C-C and C-O bond formations resulting in construction of the pentacyclic meroterpenoid skeleton...
April 19, 2018: Organic Letters
Frank Weinhold, Davood Nori-Shargh
We describe a unified picture of symmetry-breaking electronic interactions that are usually described as "pseudo Jahn-Teller (PJT) effects" and attributed to vibronic coupling, but can also be associated with hyperconjugative donor-acceptor interactions in the framework of natural bond orbital (NBO) and natural resonance theory (NRT) analysis. We show how NBO/NRT descriptors offer a simplified alternative to the vibronic coupling picture of PJT effects that yields both improved cause-effect specificity and chemically enriched understanding of symmetry-breaking phenomena, but with no necessary input from ground-state vibrational or excited-state electronic properties...
April 19, 2018: Journal of Physical Chemistry. A
Miriam Schaider, Tone Novak, Christian Komposch, Hans-Jörg Leis, Günther Raspotnig
The homologous and phylogenetically old scent glands of harvestmen-also called defensive or repugnatorial glands-represent an ideal system for a model reconstruction of the evolutionary history of exocrine secretion chemistry ("phylogenetic chemosystematics"). While the secretions of Laniatores (mainly phenols, benzoquinones), Cyphophthalmi (naphthoquinones, chloro-naphthoquinones, methyl-ketones) and some Eupnoi (naphthoquinones, ethyl-ketones) are fairly well studied, one open question refers to the still largely enigmatic scent gland chemistry of representatives of the suborder Dyspnoi and the relation of dyspnoan chemistry to the remaining suborders...
2018: Chemoecology
Majid M Heravi, Vahideh Zadsirjan, Masumeh Malmir
Tetrahydroisoquinolines are the framework of numerous natural products predominantly alkaloids, an important and one of the most wide spread families of naturally occurring compounds in the plant kingdom. Tetrahydroisoquinolines are commonly constructed through an old reaction, the so-called Pictet–Spengler Reaction (PSR). In this reaction, a β-aryl ethylamine undergoes an acid mediated condensation with a suitable aldehyde or ketone, followed by ring closure. In this review, we aim to highlight the applications of the asymmetric variant of this old name reaction in the total synthesis of natural products, chiefly, alkaloids, which exhibit significant biological properties...
April 18, 2018: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Sergey A Dobrynin, Yuri I Glazachev, Yuri V Gatilov, Elena Ilinichna Chernyak, George E Salnikov, Igor A Kirilyuk
A simple method of synthesis of sterically shielded pyrrolidine nitroxides, including title compound, have been suggested. The key procedure implies assembling of pyrrolidine ring from α-aminoacid, ketone and activated alkene in a three-component domino process with following oxidation to nitrone and Grignard reagent addition. The new nitroxides demonstrate very high stability to reduction with ascorbate.
April 18, 2018: Journal of Organic Chemistry
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