bluuebunny/crossref_metadata_2025_split huggingface dataset:
The acyltransferase activity of lipase CAL‐A allows efficient fatty acid esters formation from plant oil even in an aqueous environment
Authors: Müller Janett , Sowa Miriam A. , Dörr Mark , Bornscheuer Uwe T. 
Published: July 2015

The enzymatic synthesis of fatty acid esters (FAE) can be performed by lipases in reaction systems in the absence of bulk water. However, some lipases such as Candida antarctica lipase A (CAL‐A) have an acyltransferase activity, which enables FAE synthesis from natural oils and suitable alcohols even in the presence of water. The ability to generate these compounds in an aqueous system would be interesting for an industrial application, because this could lead to a more cost‐efficient and environmentally friendly process as the alcohol donor also serves as solvent. Using refined palm kernel oil (PKO) the CAL‐A‐catalyzed ester synthesis was studied with methanol or ethanol in the presence of 5–10% (w/w) water. Optimizing reaction parameters (e.g., temperature and water content) resulted in up to 95% ester formation after 24 h. In addition, methanol allowed higher ester formation than ethanol.Practical applications: The enzymatic synthesis of fatty acid esters from plant oils using standard lipases is hampered by the fact that the presence of water leads to undesired formation of free fatty acids. The use of CAL‐A with its unique acyltransferase activity overcomes this limitation and hence makes the industrial scale synthesis of these esters more feasible. The identification of important parameters influencing the ester formation is crucial to establish such processes.Optimization of reaction conditions leads to protocols suitable to use lipase CAL‐A in a water containing system for the synthesis of fatty acid methyl or ethyl esters in up to 95% concentration.
Pd‐Catalyzed Allylic Alkynylation of Allylic Acetates with Terminal Alkynes
Authors: Yang Qingjing , Zhou Yongyun , Chen Jingchao , He Xiaobo , Xu Jianbin , Kwong Fuk Yee , Fan Baomin 
Published: July 2015

AbstractThe first palladium‐catalyzed allylic alkynylation reaction of allylic acetates with terminal alkynes has been realized. By empolying AgOTf as a cooperative catalyst, 1,4‐enynes were synthesized in up to 98 % yield under mild conditions. Moreover, the possible asymmetric version of this allylic alkynylation reaction was demonstrated.
Chiral Squaramide‐Catalyzed Michael/­Alkylation Cascade Reaction for the Asymmetric Synthesis of Nitro‐Spirocyclopropanes
Authors: Zhao Bo‐Liang , Du Da‐Ming 
Published: July 2015

AbstractA new diastereoselective and enantioselective cyclopropanation reaction has been developed by employing a Michael/alkylation cascade reaction between (E)‐3‐arylenechroman‐4‐one or (E)‐2‐arylideneindan‐1‐one derivatives and a bromonitroalkane with a chiral squaramide catalyst. This reaction constitutes a facile asymmetric synthesis for nitro‐spirocyclopropanes that have three adjacent stereogenic centers, including one quaternary center, in moderate to good yields (up to 90 %) with excellent enantio‐ [up to >99 % ee (enantiomeric excess)] and diastereoselectivities [up to >99:1 dr (diastereomeric ratio)].
An Efficient Stereoselective Total Synthesis of All Stereoisomers of the Antibiotic Thiamphenicol through Ruthenium‐Catalyzed Asymmetric Reduction by Dynamic Kinetic Resolution
Authors: Perez Marc , Echeverria Pierre‐Georges , Martinez‐Arripe Elsa , Ez Zoubir Mehdi , Touati Ridha , Zhang Zhaoguo , Genet Jean‐Pierre , Phansavath Phannarath , Ayad Tahar , Ratovelomanana‐Vidal Virginie 
Published: July 2015

AbstractThiamphenicol is a widely used antibiotic that exhibits activity against numerous Gram‐positive and Gram‐negative pathogens. Here, we describe the expedient synthesis of its four stereoisomers through a dynamic kinetic resolution that follows a ruthenium‐catalyzed asymmetric hydrogenation or a hydrogen transfer reaction as the key step.
Enzymatic Synergism in the Synthesis of β‐Keto Esters
Authors: Wiśniewska Catalina , Koszelewski Dominik , Zysk Małgorzata , Kłossowski Szymon , Żądło Anna , Brodzka Anna , Ostaszewski Ryszard 
Published: July 2015

AbstractReaction of alcohols with ethyl and tert‐butyl acetoacetate catalyzed by a combination of commercially available enzymes is shown to be a convenient method for the preparation of a range of acetoacetic acid derivatives. Systematic studies proved that the combination of two or more enzymes enhances the yield of the reaction. Application of the selected enzyme mixture for enzymatic transesterification of various β‐keto esters provided the respective products in excellent yields up to 96 % and quantitative within 24 and 48 hours, respectively. The presented methodology is simple and mild, and can be used to prepare acetoacetates from primary and secondary alcohols.
Water‐Soluble Maleimide‐Modified Gold Nanoparticles (AuNPs) as a Platform for Cycloaddition Reactions
Authors: Ghiassian Sara , Gobbo Pierangelo , Workentin Mark S. 
Published: July 2015

AbstractMaleimide‐terminated triethylene glycol thiolate monolayer‐protected gold nanoparticles (Mal‐EG4‐AuNPs) with a core size of 2.5 ± 0.7 nm were prepared. Mal‐EG4‐AuNPs were modified in high yields via interfacial 1,3‐dipolar cycloaddition and Diels–Alder reactions with a variety of nitrones and dienes, respectively. The resulting cycloadduct‐modified AuNPs were characterized using 1H NMR spectroscopy and were verified by comparison of the spectra to those of the products of the model reactions with the same nitrones and dienes. TEM analysis showed that the reaction conditions did not affect the shape or size of the gold core, suggesting that this is an efficient methodology to modify small water soluble AuNPs under ambient pressure and biological temperature with high yields and a reasonable reaction time.
Synthesis of Building Blocks for Carbopeptoids and Their Triazole Isoster Assembly
Authors: Rjabovs Vitālijs , Ostrovskis Pāvels , Posevins Daniels , Kiseļovs Gļebs , Kumpiņš Viktors , Mishnev Anatoly , Turks Māris 
Published: July 2015

AbstractSynthetic approaches to new N‐protected γ‐ and δ‐furanoid sugar amino acids (SAAs) or tetrahydrofuran amino acids were developed. SAAs have emerged as valuable building blocks for the syntheses of peptide mimetics, so‐called carbopeptoids. 3‐C‐Substituted 1,2‐O‐isopropylidene‐α‐D‐allofuranose derivatives were used as starting materials. The designed SAAs contain either cis‐ or trans‐oriented C(3)‐aminomethyl and C(4)‐ or C(5)‐carboxylic acid functional groups attached to the 1,2‐O‐isopropylidene furanoid core, thus providing different spatial arrangements. Short‐chain homooligomers derived from a γ‐SAA and from a δ‐SAA were synthesized as the initial step towards exploration of new carbopeptoids. The key intermediates of these SAA syntheses can easily be transformed into the corresponding molecules containing azide and terminal alkyne moieties and as such have potential for future use for the syntheses of 1,2,3‐triazole isosters of peptides.
A Single Lipase‐Catalysed One‐Pot Protocol Combining Aminolysis Resolution and Aza‐Michael Addition: An Easy and Efficient Way to Synthesise β‐Amino Acid Esters
Authors: Xu Fan , Wu Qiongsi , Chen Xiaoyang , Lin Xianfu , Wu Qi 
Published: July 2015

AbstractA novel one‐pot protocol combining aza‐Michael addition and aminolysis resolution was developed to obtain chiral β‐amino acid esters with lipase B from Candida antarctica (CAL‐B) as the only catalyst. This method is conducted under mild reaction conditions and is very easy to handle. After a series of detailed optimization studies, ten racemic aromatic or aliphatic amines were subjected to this one‐pot procedure, and twelve chiral β‐amino acid esters and ten chiral amides were successfully synthesised with excellent ee values in theoretical yields. Scaled‐up procedures also worked without apparent reduction in reaction rate or enantioselectivity, which makes this method suitable for large‐scale production of chiral β‐amino acid esters.
Synthesis of (R)‐BINOL‐Derived (Cyclopentadienone)iron Complexes and Their Application in the Catalytic Asymmetric Hydrogenation of Ketones
Authors: Gajewski Piotr , Renom‐Carrasco Marc , Facchini Sofia Vailati , Pignataro Luca , Lefort Laurent , de Vries Johannes G. , Ferraccioli Raffaella , Piarulli Umberto , Gennari Cesare 
Published: July 2015

AbstractA family of chiral (cyclopentadienone)iron complexes, featuring an (R)‐BINOL‐derived backbone, and their application in the asymmetric hydrogenation of ketones are described. The complexes differ from each other in the substituents at the 3,3′‐positions of the binaphthyl residue (H, OH, OR, OCOR, OSO2R) or at the 2,5‐positions of the cyclopentadienone ring [trimethylsilyl (TMS) or Ph]. Remarkably, eight precatalysts with different 3,3′‐binaphthyl substitution [(R)‐1c–1j] were synthesized from a common parent complex [(R)‐1b] through direct functional group interconversion reactions of the complexes. The 3,3′‐(bis)methoxy‐substituted precatalyst (R)‐1b gave the best catalytic performance, and its application scope was assessed in the hydrogenation of several ketones. The observed ee values (up to 77 %) are much higher than those previously reported for other chiral (cyclopentadienone)iron complexes.
Analysis of the anti‐allodynic effects of combination of a synthetic cannabinoid and a selective noradrenaline re‐uptake inhibitor in nerve injury‐induced neuropathic mice
Authors: Gunduz O. , Topuz R.D. , Karadag C.H. , Ulugol A. 
Published: July 2015

AbstractBackgroundCombining drugs not only reduces specific adverse effects of each of the drug at a higher dose but also may lead to enhanced efficacy. Tapentadol is a recently discovered analgesic possessing μ‐opioid receptor agonism and noradrenaline re‐uptake inhibition in a single molecule. Taking into consideration, the pharmacological similarities between opioids and cannabinoids, we assumed that combination of cannabinoids with noradrenaline re‐uptake inhibitors might also be effective. We therefore aimed to determine whether combining 1:1, 1:3 and 3:1 fixed ratios of the synthetic cannabinoid WIN 55,212‐2 and the selective noradrenaline re‐uptake inhibitor maprotiline exert anti‐allodynic synergy on nerve‐injured neuropathic mice.MethodsPartial tight ligation of the sciatic nerve was made in mice; on pre‐operative and post‐operative 15 days basal mechanical allodynia, cold allodynia and motor function were assessed using von Frey filaments, hot/cold plate and rota rod apparatus.ResultsMechanical and cold allodynia developed in all groups on post‐operative 15 days. Development of cold allodynia was statistically significant in all groups (p < 0.05); therefore, cold allodynia was used in combination studies. As shown by isobolographic analysis, interactions of 1:1 and 3:1 ratios of WIN 55,212‐2:maprotiline combinations were supra‐additive, whereas 1:3 ratio was sub‐additive.ConclusionsOverall, our data suggest that combination of a cannabinoid with a selective noradrenaline re‐uptake inhibitor may offer a beneficial treatment option for neuropathic pain.
Switchable Bioelectrocatalysis Controlled by pH Changes
Authors: Katz Evgeny , Fernández Víctor M. , Pita Marcos 
Published: July 2015

AbstractApplication of stimuli‐responsive materials, particularly based on pH‐sensitive monolayers and thin‐films, to switchable bioelectrocatalysis is briefly overviewed in the paper. The switchable systems are exemplified with amino‐functionalized self‐assembled monolayers, polyelectrolyte brushes and complex biomolecular assemblies organized on electrode surfaces and demonstrating different electrochemical properties depending on pH values. The pH variation was achieved in situ due to biocatalytic reactions, thus coupling switchable bioelectrocatalysis with enzyme‐catalyzed reaction cascades. Future developments leading to complex biomolecular systems with switchable and tunable bioelectronics properties are envisaged as the result of research in this area.
Solution or Gas Phase? Oxidation and Radical Formation in Electrospray Ionization Mass Spectrometry (ESI MS)
Authors: Iftikhar Imran , Brajter‐Toth Anna 
Published: July 2015

AbstractThe relationship between one‐electron (e−) oxidation processes and the formation of radical cations of endogenous and exogenous compounds in vivo is of considerable interest. This paper reports on the experiments that allow FTICR mass spectrometric (MS) detection of ion signals that are consistent with the formation of radical cations of caffeine (CA) and theophylline (TP) during electrospray ionization (ESI) in ESI FTICR MS and in on‐line electrochemistry (EC)/ESI FTICR MS in positive mode. Significantly, the signals of the radicals of CA•+ and TP•+can be enhanced by simple modifications of the operating conditions in ESI MS, facilitating investigations of radical formation and related reactions.
Construction of Modified Carbon Paste Electrode for Highly Sensitive Simultaneous Electrochemical Determination of Trace Amounts of Copper (II) and Cadmium (II)
Authors: Afkhami Abbas , Soltani‐Shahrivar Morteza , Ghaedi Hamed , Madrakian Tayyebeh 
Published: July 2015

AbstractA chemically modified electrode was constructed for rapid, simple, accurate, selective and highly sensitive simultaneous determination of Cu(II) and Cd(II) using square wave anodic stripping voltammetry. The electrode was prepared by incorporation of SiO2 nanoparticles, coated with a newly synthesized Schiff base, in carbon paste electrode. The limit of detection was found to be 0.28 ng mL−1 and 0.54 ng mL−1 for Cu(II) and Cd(II), respectively. The proposed chemically modified electrode was used for the determination of copper and cadmium in several foodstuffs and water samples.
Sequential Voltammetric Determination of Uranium, Cadmium and Lead by Using the ex situ Bismuth Film Electrode: Application to Phosphate Fertilizers
Authors: Jost Cristiane L. , di Martos Lara M. , Ferraz Luis , do Nascimento Paulo Cícero 
Published: July 2015

AbstractA sequential voltammetric procedure for the determination of uranium, cadmium and lead was investigated at an ex situ bismuth film electrode (BiFE). First, the adsorptive stripping voltammetry was applied to assay the U(VI)‐cupferron complex in the differential pulse mode (detection limit of 1.0 µg L−1, 200 s accumulation time). Through the manipulation of the same aliquot of the sample, efforts were made to quantify cadmium and lead by square wave anodic stripping voltammetry. Detection limits of 2.03 µg L−1 for Cd (II) and 2.43 µg L−1 for Pb (II) were calculated (100 s accumulation time). The methodology was successfully applied to phosphate fertilizer samples after open vessel wet decomposition (HNO3/H2O2). The following value ranges were evaluated: U (VI) 37.2–150 mg kg−1, Pb (II) 78.3–204 mg kg−1 and Cd (II) 44.1–71.6 mg kg−1. Validation was performed by using the standard reference materials SRM‐695 – phosphate fertilizer – and SRM‐1643e – water.
TiO2 Nanomaterials as Anode Materials for Lithium‐Ion Rechargeable Batteries
Authors: Yan Xiaodong , Wang Zhihui , He Min , Hou Zhaohui , Xia Ting , Liu Gao , Chen Xiaobo 
Published: July 2015

AbstractWith the increased focus on sustainable energy, Li‐ion rechargeable batteries are playing more important roles in energy storage and utilization. Owing to their high safety, low cost, and moderate capacity, titanium dioxide (TiO2) nanomaterials have been considered as promising alternative anode materials for Li‐ion rechargeable batteries. Here, we present a concise overview of past research efforts on TiO2 nanomaterials as anode materials for Li‐ion rechargeable batteries. We focus on research examples that illustrate the importance of the nanometer‐scale, shape, dimensionality, and morphology of the TiO2 nanomaterials to their electrochemical properties for Li‐ion storage. Representative examples are given for nanoparticles, nanowires, nanotubes, nanosheets, and three‐dimensional materials, as well as amorphous structures. Approaches to improve the performance of TiO2 nanomaterials such as carbon coating, bulk doping, self‐structural modification, and compositing are surveyed briefly. Progress in the use of TiO2 nanomaterials in full‐cell configurations is also reviewed. Finally, the challenges for the practical applications of TiO2 nanomaterials in Li‐ion rechargeable batteries are discussed briefly.
Investigation of K2CO3‐Catalyzed Pyrolysis and Steam Gasification of Coal Char
Authors: Zhu Huaili , Wang Ximing , Zhang Jingang , Yao Kui , Yu Guangsuo , Wang Xingjun 
Published: July 2015

AbstractPyrolysis and steam gasification experiments of coal char with and without K2CO3 were performed using a thermogravimetric analyzer to investigate the effect of catalyst loading method on gasification reactivity at different temperatures (650–800 °C), and an additional redox cycle experiment of catalyzed char‐steam gasification was conducted in a fixed‐bed reactor. The results showed that, at low temperature, the solution impregnation method had a larger effect on the gasification reactivity than the physical blending method; at temperatures above 700 °C, the differences of two methods diminished due to the high mobility of potassium. In catalytic pyrolysis, the release of CO and CO2 indicated that K2CO3 reacted with carbon. The redox cycle experiments suggest that the potassium reacted with carbon to produce intermediates of the form K2O2C, K2OC, and K2C. The K2C intermediate may help to explain the release of more H2 during the initial period of catalytic coal char–steam gasification.
Decamethylcyclopentasiloxane (D5) environmental sources, fate, transport, and routes of exposure
Authors: Mackay Donald , Cowan-Ellsberry Christina E. , Powell David E. , Woodburn Kent B. , Xu Shihe , Kozerski Gary E. , Kim Jaeshin 
Published: July 2015

Abstract

The environmental sources, fate, transport, and routes of exposure of decamethylcyclopentasiloxane (D5; CAS no. 541-02-6) are reviewed in the present study, with the objective of contributing to effective risk evaluation and assessment of this and related substances. The present review, which is part of a series of studies discussing aspects of an effective risk evaluation and assessment, was prompted in part by the findings of a Board of Review undertaken to comment on a decision by Environment Canada made in 2008 to subject D5 to regulation as a toxic substance. The present review focuses on the early stages of the assessment process and how information on D5's physical–chemical properties, uses, and fate in the environment can be integrated to give a quantitative description of fate and exposure that is consistent with available monitoring data. Emphasis is placed on long-range atmospheric transport and fate in water bodies receiving effluents from wastewater treatment plants (along with associated sediments) and soils receiving biosolids. The resulting exposure estimates form the basis for assessments of the resulting risk presented in other studies in this series. Recommendations are made for developing an improved process by which D5 and related substances can be evaluated effectively for risk to humans and the environment. Environ Toxicol Chem 2015;34:2689–2702. © 2015 The Authors. Environmental Toxicology and Chemistry Published by Wiley Periodicals, Inc. on behalf of SETAC
Fugacity and activity analysis of the bioaccumulation and environmental risks of decamethylcyclopentasiloxane (D5)
Authors: Gobas Frank A.P.C. , Xu Shihe , Kozerski Gary , Powell David E. , Woodburn Kent B. , Mackay Don , Fairbrother Anne 
Published: July 2015

Abstract

As part of an initiative to evaluate commercial chemicals for their effects on human and environmental health, Canada recently evaluated decamethylcyclopentasiloxane (D5; CAS no. 541-02-06), a high–volume production chemical used in many personal care products. The evaluation illustrated the challenges encountered in environmental risk assessments and the need for the development of better tools to increase the weight of evidence in environmental risk assessments. The present study presents a new risk analysis method that applies thermodynamic principles of fugacity and activity to express the results of field monitoring and laboratory bioaccumulation and toxicity studies in a comprehensive risk analysis that can support risk assessments. Fugacity and activity ratios of D5 derived from bioaccumulation measures indicate that D5 does not biomagnify in food webs, likely because of biotransformation. The fugacity and activity analysis further demonstrates that reported no-observed-effect concentrations of D5 normally cannot occur in the environment. Observed fugacities and activities in the environment are, without exception, far below those corresponding with no observed effects, in many cases by several orders of magnitude. This analysis supports the conclusion of the Canadian Board of Review and the Minister of the Environment that D5 does not pose a danger to the environment. The present study further illustrates some of the limitations of a persistence-bioaccumulation-toxicity–type criteria-based risk assessment approach and discusses the merits of the fugacity and activity approach to increase the weight of evidence and consistency in environmental risk assessments of commercial chemicals. Environ Toxicol Chem 2015;34:2723–2731. © 2015 The Authors. Environmental Toxicology and Chemistry Published by Wiley Periodicals, Inc. on behalf of SETAC.
Characterization of ecological risks from environmental releases of decamethylcyclopentasiloxane (D5)
Authors: Fairbrother Anne , Burton G. Allen , Klaine Stephen J. , Powell David E. , Staples Charles A. , Mihaich Ellen M. , Woodburn Kent B. , Gobas Frank A.P.C. 
Published: July 2015

Abstract

Decamethylcyclopentasiloxane (D5) is used in personal care products and industrial applications. The authors summarize the risks to the environment from D5 based on multiple lines of evidence and conclude that it presents negligible risk. Laboratory and field studies show that D5 is not toxic to aquatic organisms or benthic invertebrates up to its solubility limit in water or porewater or its sorptive capacity in sediment. Comparison of lipid-normalized internal concentrations with measured concentrations in benthos indicates that field-collected organisms do not achieve toxic levels of D5 in their tissues, suggesting negligible risk. Exposure to D5 resulted in a slight reduction of root biomass in barley at test concentrations 2 orders of magnitude greater than measured D5 levels in biosolids-amended soils and more than twice as high as the maximum calculated sorptive capacity of the soil. No effects were observed in soil invertebrates exposed to similar concentrations, indicating that D5 poses a de minimis risk to the terrestrial environment. High rates of metabolism and elimination of D5 compared with uptake rates from food results in biodilution in the food web rather than biomagnification, culminating in de minimis risk to higher trophic level organisms via the food chain. A fugacity approach substantiates all conclusions that were made on a concentration basis. Environ Toxicol Chem 2015;34:2715–2722. © 2015 SETAC