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Decarboxylation

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https://www.readbyqxmd.com/read/28732997/sonochemical-effect-of-flat-sweep-frequency-and-pulsed-ultrasound-fsfp-treatment-on-stability-of-phenolic-acids-in-a-model-system
#1
Wenjuan Qu, Raya Masoud Sehemu, Yiting Feng, ShuangQian Shi, Juan Wang, Haile Ma, Chandrasekar Venkitasamy
To obtain greater knowledge on the stability of phenolic acids for the application of FSFP ultrasound technique in the extraction, the sonochemical effects of ultrasonic factors were investigated. The kinetic model and mechanism of degradation reaction were developed and identified by FT-IR and HPLC-ESIMS. The results showed that caffeic and sinapic acids were degraded under FSFP ultrasound treatment. The ultrasonic temperature, frequency, sweep range, sweep cycle, and pulse ratio were proved to be important factors in affecting the degradation rates of caffeic and sinapic acids...
November 2017: Ultrasonics Sonochemistry
https://www.readbyqxmd.com/read/28727245/stereospecific-decarboxylative-nazarov-cyclization-mediated-by-carbon-dioxide-for-preparation-of-highly-substituted-2-cyclopentenones
#2
Keiichi Komatsuki, Yuta Sadamitsu, Kohei Sekine, Kodai Saito, Tohru Yamada
Highly-substituted 2-cyclopentenones were stereospecifically and regioselectively constructed with a high catalytic efficiency through the Lewis-acid catalyzed decarboxylative Nazarov cyclization of the cyclic carbonate derivative, prepared by the reaction of the propargyl alcohol with carbon dioxide in the presence of a silver catalyst. The stereochemistry of the 2-cyclopentenone could be strictly controlled by the geometry of the alkene in the starting material. This method was applicable for various substrates...
July 20, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28726425/ruthenium-ii-catalyzed-hydroarylation-of-maleimides-using-carboxylic-acids-as-a-traceless-directing-group
#3
Anup Mandal, Harekrishna Sahoo, Suman Dana, Mahiuddin Baidya
An efficient Ru(II)-catalyzed hydroarylation of maleimides with ready-stock aryl carboxylic acids has been developed based on weak carboxylate-directed ortho-C-H alkylation and concomitant decarboxylation processes, fabricating 3-aryl succinimides, a recurrent scaffold in drug molecules, in high yields (up to 97%). The protocol features operational simplicity, avoids the need for precious metal additives/oxidants, and offers broad substrate scope with formal meta- and para-selectivities. It represents the first example of Ru(II)-catalyzed direct arylation of maleimides with unbiased benzoic acids...
July 20, 2017: Organic Letters
https://www.readbyqxmd.com/read/28726419/hitoyol-a-and-b-two-norsesquiterpenoids-from-the-basidiomycete-coprinopsis-cinerea
#4
Junnosuke Otaka, Daisuke Hashizume, Yui Masumoto, Atsuya Muranaka, Masanobu Uchiyama, Hiroyuki Koshino, Yushi Futamura, Hiroyuki Osada
Hitoyol A (1), an unprecedented norsesquiterpenoid with an exo-tricyclo[5.2.1.0(2,6)]decane skeleton, was isolated from the culture broth of Basidiomycete Coprinopsis cinerea along with a novel skeletal hitoyol B (2) containing 4-cyclopentene-1,3-dione. Their structures and absolute configurations were analyzed by single-crystal X-ray diffraction and electronic circular dichroism spectroscopic methods. Compound 1 is possibly biosynthesized through decarboxylation-induced cyclization of lagopodin B, a known cuparene-type sesquiterpenoid...
July 20, 2017: Organic Letters
https://www.readbyqxmd.com/read/28718961/photodegradation-kinetics-transformation-and-toxicity-prediction-of-ketoprofen-carprofen-and-diclofenac-acid-in-aqueous-solutions
#5
Jian Li, Li-Yun Ma, Lu-Shuang Li, Li Xu
In this study, the photodegradation of three commonly used non-steroidal anti-inflammatory drugs, ketoprofen (KET), carprofen (CAR) and diclofenac acid (DIC), was conducted under UV irradiation. The kinetic results showed that the studied three pharmaceuticals obeyed to the first-order reaction with the decreasing rate constants of 1.54×10(-4) s(-1) , 5.91×10(-5) s(-1) and 7.78×10(-6) s(-1) for CAR, KET and DIC, respectively. Moreover, the main transformation products (TPs) were identified by ion-pair liquid-liquid extraction combined with injection port derivatization-gas chromatography-mass spectrometer and high performance liquidchromatography-quadrupole-time of flight mass spectrometer analysis...
July 18, 2017: Environmental Toxicology and Chemistry
https://www.readbyqxmd.com/read/28714686/an-unconventional-redox-cross-claisen-condensation-aromatization-of-4-hydroxyprolines-with-ketones
#6
Mi Tang, Rengwei Sun, Hao Li, Xinhong Yu, Wei Wang
Reaction of α-amino acids particularly prolines and their derivatives with carbonyl compounds via decarboxylative redox process is a viable strategy for synthesis of structurally diverse nitrogen centered heterocyclics. In these processes, the decarboxylation is the essential driving force for the processes. The realization of the redox process without decarboxy-lation may offer an opportunity to explore new reactions. Herein, we report the discovery of an unprecedented redox Claisen type condensation aromatization cascade reaction of 4-substituted 4-hydroxyproline and its esters with unreactive ketones...
July 17, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28711707/protecting-group-free-radical-decarboxylation-of-bile-acids-synthesis-of-novel-steroidal-substituted-maleic-anhydrides-and-maleimides-and-evaluation-of-their-cytotoxicity-on-c6-rat-glioma-cells
#7
Mohammad Samadi, Thomas Nury, Ali Khalafi-Nezhad, Gérard Lizard
We report the first Barton radical decarboxylation of unprotected bile acids via in situ irradiation of their thiohydroxamic esters in the presence of citraconic anhydride and citracoimide, leading to the synthesis a series of steroidal maleic anhydrides and maleimides as novel hybrid bile acids. The cytotoxic activities were evaluated on C6 rat glioma cells.
July 12, 2017: Steroids
https://www.readbyqxmd.com/read/28707104/microbial-hydrocarbon-formation-from-biomass
#8
Adrie J J Straathof, Maria C Cuellar
Fossil carbon sources mainly contain hydrocarbons, and these are used on a huge scale as fuel and chemicals. Producing hydrocarbons from biomass instead is receiving increased attention. Achievable yields are modest because oxygen atoms need to be removed from biomass, keeping only the lighter carbon and hydrogen atoms. Microorganisms can perform the required conversions, potentially with high selectivity, using metabolic pathways that often end with decarboxylation. Metabolic and protein engineering are used successfully to achieve hydrocarbon production levels that are relevant in a biorefinery context...
July 14, 2017: Advances in Biochemical Engineering/biotechnology
https://www.readbyqxmd.com/read/28705010/isocitrate-dehydrogenase-mutation-as-a-therapeutic-target-in-gliomas
#9
Catherine H Han, Tracy T Batchelor
Isocitrate dehydrogenases (IDH) are important enzymes that catalyze the oxidative decarboxylation of isocitrate to α-ketoglutarate (α-KG), producing NADPH in the process. More than 80% of low-grade gliomas and secondary glioblastoma (GBM) harbor an IDH mutation. IDH mutations involve the catalytic pocket of the enzyme and lead to a neomorphic ability to produce 2-hydroxyglutarate (2HG) while oxidizing NADPH to NADP+. 2HG is considered as an 'oncometabolite' which is thought to be responsible for many, if not all, biologic effects of IDH mutations...
June 2017: Chinese Clinical Oncology
https://www.readbyqxmd.com/read/28704903/enchancement-of-gamma-aminobutyric-acid-production-by-co-localization-of-neurospora-crassa-or74a-glutamate-decarboxylase-with-escherichia-coli-gaba-transporter-via-synthetic-scaffold-complex
#10
Sivachandiran Somasundaram, Murali Kannan Maruthamuthu, Irisappan Ganesh, Gyeong Tae Eom, Soon Ho Hong
Gamma-aminobutyric acid is a precusor of nylon-4, which is a promising heat-resistant biopolymer. GABA can be produced from the decarboxylation of glutamate by glutamate decarboxylase. In this study, a synthetic scaffold complex strategy was employed involving Neurospora crassa glutamate decarboxylase (GadB) and Escherichia coli GABA antiporter (GadC) to improve GABA production. To construct the complex, the SH3 domain was attached to the N. crassa GadB, and SH3 ligand was attached to the N-terminus, middle and C-terminus of E...
July 14, 2017: Journal of Microbiology and Biotechnology
https://www.readbyqxmd.com/read/28701039/aminofutalosine-synthase-evidence-for-captodative-and-aryl-radical-intermediates-using-beta-scission-and-srn1-trapping-reactions
#11
Sumedh Joshi, Nilkamal Mahanta, Dmytro Fedoseyenko, Howard J Williams, Tadhg P Begley
Aminofutalosine synthase (MqnE) is a radical SAM enzyme involved in the menaquinone biosynthetic pathway. In this communication, we propose a novel mechanism for this reaction involving the addition of the adenosyl radical to the substrate double bond to form a captodative radical followed by rearrangement and decarboxylation to form an aryl radical anion which is then oxidized by the [4Fe-4S]+2 cluster. Consistent with this proposal, we describe the trapping of the captodative radical and the aryl radical anion using radical triggered C-Br fragmentation reactions...
July 12, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28697551/n-acyl-homoserine-lactone-dynamics-during-biofilm-formation-of-a-1-2-4-trichlorobenzene-mineralizing-community-on-clay
#12
Hongjie Sheng, Mourad Harir, Lisa A Boughner, Xin Jiang, Philippe Schmitt-Kopplin, Reiner Schroll, Fang Wang
In Gram-negative bacteria, quorum sensing systems are based on the N-acyl-homoserine lactone (AHL) molecule. The objective of this study was to investigate the role of quorum sensing systems during biofilm formation by a microbial community while degrading the pollutant. Our model system included 1,2,4-trichlorobenzene (1,2,4-TCB) and its mineralizing Gram-negative bacterial community to investigate the relationships between AHL dynamics, cell growth and pollutant degradation. Biomineralization of 1,2,4-TCB was monitored for both the planktonic bacterial community with and without sterile clay particles in liquid cultures...
July 6, 2017: Science of the Total Environment
https://www.readbyqxmd.com/read/28694454/graphene-oxide-sheets-combine-into-conductive-coatings-by-direct-oxidative-electropolymerization
#13
S Halevy, Y Bochlin, Y Kadosh, A Kaplan, H Avraham, A Nissim, R Ben Hamo, T Ohaion-Raz, E Korin, A Bettelheim
New coatings are obtained when graphene oxide is further oxidized at moderate anodic potentials (≤~1.3 V vs. Ag/AgCl). Based on a variety of spectroscopic and electrochemical observations, the coatings are attributed to the direct electropolymerization of graphene oxide sheets via oxidation of the phenol edge groups on graphene. Depending on the applied potential, ether or carboxylic groups are formed. The coatings obtained via further oxidation are characterized by a lower O/C ratio due to decarboxylation and a higher content of C=C bonds...
July 10, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28692260/chemo-and-regio-selective-organo-photoredox-catalyzed-hydro-formylation-of-styrenes-via-a-radical-pathway
#14
He Huang, Chenguang Yu, Yueteng Zhang, Yongqiang Zhang, Patrick S Mariano, Wei Wang
An unprecedented, chemo- and regio-selective, organo-photoredox catalyzed hydroformylation reaction of aryl olefins with diethoxyacetic acid as the formylation reagent is described. In contrast to traditional transition metal promoted ionic hydroformylation reactions, the new process follows a unique photoredox promoted, free radical pathway. In this process, a formyl radical equivalent, produced from diethoxacetic acid through a dye (4CzIPN) photocatalyzed, sequential oxidation-decarboxylation route, regio- and chemo-selectively adds to a styrene substrate...
July 10, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28687706/bone-regulates-browning-and-energy-metabolism-through-mature-osteoblast-osteocyte-ppar%C3%AE-expression
#15
Julia Brun, Flavien Berthou, Mirko Trajkovski, Pierre Maechler, Michanlegelo Foti, Nicolas Bonnet
Peroxisome proliferator-activated receptor gamma (PPARγ) is a master regulator of energy metabolism. In bone it is known to regulate osteoblast differentiation and osteoclast activity. Whether PPARγ expression in bone cells, particularly osteocytes, regulates energy metabolism remains unknown. Here we show that mature osteoblast/osteocyte-specific ablation of PPARγ in mice (Ocy-PPARγ(-/-) ) alters body composition with age, namely less fat and more lean mass and enhances insulin sensitivity and energy expenditure compared to wildtype...
July 7, 2017: Diabetes
https://www.readbyqxmd.com/read/28681966/alkyl-esterification-of-vinylarenes-enabled-by-visible-light-induced-decarboxylation
#16
Liang Ge, Yajun Li, Wujun Jian, Hongli Bao
A decarboxylative alkyl-esterification of vinylarenes induced by visible light is described. A variety of alkyl diacyl peroxides synthesized from readily available aliphatic carboxylic acids are used as not only the oxygenation source but also the alkylation source for the reaction. The reaction has a wide substrate scope, excellent yields, mild reaction conditions, and simple operation. Carbon dioxide is the sole by-product. An oxidative quenching process is proposed as the mechanism.
July 6, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28678292/photocatalytic-decarboxylation-of-diacids-for-the-initiation-of-free-radical-polymerization
#17
Wanfeng Liao, Xiuyuan Ni
Photopolymerization, which is one of the most attractive polymerization methods, has been recently studied for the development of new photoinitiators. Herein, we use a binary mixture of titanium dioxide (TiO2) nanoparticles and carboxylic diacid as a novel photoinitiator to initiate the free radical polymerization of vinyl acetate (VAc). The polymerization of VAc is achieved both in aqueous medium and bulk. The initiation mechanism of TiO2/diacids is studied via nuclear magnetic resonance (NMR) spectroscopy using (13)C labeled diacids as probing molecules...
July 5, 2017: Photochemical & Photobiological Sciences
https://www.readbyqxmd.com/read/28677397/c1-azacycloalkyl-hexahydrocannabinols
#18
Thanh C Ho, Naoyuki Shimada, Marcus A Tius, Spyros P Nikas, Wen Zhang, Alexandros Makriyannis
We report the design, synthesis, and biological evaluation of a novel class of cannabinergic ligands namely C1'-azacycloalkyl hexahydrocannabinols. Our synthetic approaches utilize an advanced common chiral intermediate triflate from which all analogs could be derived. Key synthetic steps involve microwave assisted Liebeskind-Srogl C-C cross-coupling and palladium-catalyzed decarboxylative coupling reactions. The C1'-N-methyl-azetidinyl- and C1'-N-methyl-pyrrolidinyl-analogs were found to be high affinity ligands for the CB1 and CB2 cannabinoid receptors...
July 5, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28677251/ketone-formation-from-carboxylic-acids-by-ketonic-decarboxylation-the-exceptional-case-of-the-tertiary-carboxylic-acids
#19
Borja Oliver-Tomas, Michael Renz, Avelino Corma
For the reaction mechanism of the ketonic decarboxylation of two carboxylic acids, a β-keto acid is favored as key intermediate in many experimental and theoretical studies. Hydrogen atoms in α-position are an indispensable requirement for the substrates to react following this mechanism. However, isolated literature observations with tertiary carboxylic acids are not in accordance with it and these are revisited and discussed herein. The experimental results obtained with pivalic acid indicated that the ketonic decarboxylation does not occur with this substrate...
July 5, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28671210/a-mechanistic-study-of-the-non-oxidative-decarboxylation-catalyzed-by-the-radical-s-adenosyl-l-methionine-enzyme-blse-involved-in-blasticidin-s-biosynthesis
#20
Lei Liu, Xinjian Ji, Yongzhen Li, Wenjuan Ji, Tianlu Mo, Wei Ding, Qi Zhang
Decarboxylation is a fundamentally important reaction in biology and involves highly diverse mechanisms. Here we report a mechanistic study of the non-oxidative decarboxylation catalyzed by BlsE, a radical S-adenosyl-l-methionine (SAM) enzyme involved in blasticidin S biosynthesis. Through a series of biochemical analysis with isotopically labeled reagents, we show that the BlsE-catalyzed reaction is initiated by the 5'-deoxyadenosyl (dAdo) radical-mediated hydrogen abstraction from a sugar carbon of the substrate cytosylglucuronic acid (CGA), and does not involve a carboxyl radical as has been proposed for 4-hydroxyphenylacetate decarboxylase (HPAD)...
July 3, 2017: Chemical Communications: Chem Comm
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