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Xinfei Chen, Xiaoqian Ma, Xiaowei Peng, Yousheng Lin, Zhongliang Yao
Hydrothermal carbonization (HTC) of sweet potato waste was performed to investigate the effect of process parameters including reaction temperature (180-300 °C) and residence time (0-120 min) on the characteristics of hydrochars. The results showed that the increase of reaction temperature and residence time both decreased the yield of hydrochars. With the increase of reaction temperature and residence time, the carbon content of hydrochars increased, while the hydrogen and oxygen contents decreased. The lower H/C and O/C ratios indicated that dehydration and decarboxylation reactions occurred during HTC...
November 1, 2017: Bioresource Technology
Se Wang, Zhuang Wang
The study of pollution due to combined antibiotics and metals is urgently needed. Photochemical processes are an important transformation pathway for antibiotics in the environment. The mechanisms underlying the effects of metal-ion complexation on the aquatic photochemical transformation of antibiotics in different dissociation forms are crucial problems in science, and beg solutions. Herein, we investigated the mechanisms of direct photolysis of norfloxacin (NOR) in different dissociation forms in water and metal ion Mg(2+) effects using quantum chemical calculations...
November 11, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Weixu Kong, Daniel Romo
The utility of the nucleophile-catalyzed (Lewis base) aldol lactonization (NCAL) process for the diastereo- and enantioselective synthesis of N-heterocycle-fused-β-lactones from N-linked ketoacids is described. A series of bi- and tricyclic, N-heterocycle-fused, β-lactones were first synthesized in racemic fashion via the NCAL process with excellent diastereoselectivity (>19:1) utilizing 4-pyrrolidinopyridine as an effective achiral Lewis base. A catalytic, enantioselective version of this NCAL process using isothiourea catalysts provided access to bicyclic β-lactone-fused, N-heterocycles in moderate to good yields (up to 80%) with high enantiocontrol (up to >99:1 er)...
November 10, 2017: Journal of Organic Chemistry
Kun Jing, Jia-Ping Yao, Zhong-Yuan Li, Qi-Li Li, Hao-Sheng Lin, Guan-Wu Wang
A palladium-catalyzed decarboxylative ortho-acylation of tertiary benzamides with α-oxocarboxylic acids by weak O-coordination has been described. This reaction proceeds smoothly with high monoacylation selectivity, affording ortho-acylated benzamides in moderate to good yields. When secondary benzamides are employed as the substrates, the formed ortho-acylated benzamides undergo further intramolecular cyclization to provide isoindolinone derivatives. In addition, several transformations of the synthesized ortho-acylated benzamides into a diversity of synthetically valuable products have been demonstrated...
November 10, 2017: Journal of Organic Chemistry
Mateo Berton, Rossella Mello, Paul G Williard, María Elena González-Núñez
Lithium β-ketocarboxylates 1(COOLi), prepared by reaction of lithium enolates 2(Li(+)) with carbon dioxide, readily decarboxylate in THF solution unless in the presence of lithium salts, in which case they are indefinitely stable at room temperature under inert atmosphere. The availability of stable THF solutions of lithium β-ketocarboxylates 1(COOLi) in the absence of carbon dioxide allowed for reactions with nitrogen bases and alkyl halides 3 to give α-alkyl ketones 1(R) after acidic hydrolysis. The sequence then represents the use of carbon dioxide as a removable directing group for the selective monoalkylation of lithium enolates 2(Li(+))...
November 8, 2017: Journal of the American Chemical Society
Justine N deGruyter, Lara R Malins, Laurin Wimmer, Khalyd J Clay, Javier Lopez-Ogalla, Tian Qin, Josep Cornella, Zhiqing Liu, Guanda Che, Denghui Bao, Jason M Stevens, Jennifer X Qiao, Martin P Allen, Michael A Poss, Phil S Baran
Tetrachloro-N-hydroxyphthalimide tetramethyluronium hexafluorophosphate (CITU) is disclosed as a convenient and economical reagent for both acylation and decarboxylative cross-coupling chemistries. Within the former set of reactions, CITU displays reactivity similar to that of common coupling reagents, but with increased safety and reduced cost. Within the latter, increased yields, more rapid conversion, and a simplified procedure are possible across a range of reported decarboxylative transformations.
November 8, 2017: Organic Letters
Xiao-Jing Wei, Wout Boon, Volker Hessel, Timothy Noël
The development of synthetic methodologies which provide access to both stereoisomers of α,β-disubstituted olefins is a challenging undertaking. Herein, we describe the development of an operationally simple and stereoselective synthesis of difluoromethylated styrenes via a visible-light photocatalytic decarboxylation strategy using fac-Ir(ppy)3 as the photocatalyst. Meta- and para-substituted cinnamic acids provide the expected E-isomer. In contrast, ortho-substituted cinnamic acids yield selectively the less stable Z-product, whereas the E-isomer can be obtained via continuous-flow processing through accurate control of the reaction time...
October 6, 2017: ACS Catalysis
Ana Lambertos, Bruno Ramos-Molina, David Cerezo, Andrés J López-Contreras, Rafael Peñafiel
Ornithine decarboxylase (ODC) is a key enzyme in the biosynthesis of polyamines. ODC-antizyme inhibitors (AZINs) are homologous proteins of ODC, devoid of enzymatic activity but acting as regulators of polyamine levels. The last paralogue gene recently incorporated into the ODC/AZINs family is the murine Gm853, which is located in the same chromosome as AZIN2, and whose biochemical function is still unknown. By means of transfection assays of HEK293T cells with a plasmid containing the coding region of Gm853, we show here that unlike ODC, GM853 was a stable protein that was not able to decarboxylate l-ornithine or l-lysine and that did not act as an antizyme inhibitor...
November 3, 2017: Biochimica et Biophysica Acta
Anna Burniol-Figols, Cristiano Varrone, Anders Egede Daugaard, Simone Balzer Le, Ioannis V Skiadas, Hariklia N Gavala
Crude glycerol, a by-product from the biodiesel industry, can be converted by mixed microbial consortia into 1,3-propanediol (1,3-PDO) and volatile fatty acids. In this study, further conversion of these main products into polyhydroxyalkanoates (PHA) was investigated with the focus on 1,3-PDO. Two different approaches for the enrichment of PHA accumulating microbial consortia using an aerobic dynamic feeding strategy were applied. With the first approach, where nitrogen was present during the whole cycle, no net production of PHA from 1,3-PDO was observed in the fermented effluent, not even in a nitrogen-limited PHA accumulation assay...
October 23, 2017: Water Research
G Rugg, H M Senn
To rationalise mechanistically the intriguing regio- and chemoselectivity patterns for different substrates of the non-haem iron/2-oxoglutarate dependent halogenase SyrB2, it is crucial to elucidate the structure of the pivotal [Fe(IV)[double bond, length as m-dash]O] intermediate. We have approached the problem by a combination of classical and QM/MM modelling. We present complete atomistic models of SyrB2 in complex with its native substrate l-threonine as well as l-α-amino butyric acid and l-norvaline (all conjugated to the pantetheine tether), constructed by molecular docking and extensive MD simulations...
November 3, 2017: Physical Chemistry Chemical Physics: PCCP
Meredith A Skiba, Andrew P Sikkema, Nathan A Moss, Collin L Tran, Rebecca M Sturgis, Lena Gerwick, William H Gerwick, David H Sherman, Janet L Smith
Natural product biosynthetic pathways contain a plethora of enzymatic tools to carry out difficult biosynthetic transformations. Here, we discover an unusual mononuclear iron-dependent methyltransferase that acts in the initiation steps of apratoxin A biosynthesis (AprA MT1). Fe(3+)-replete AprA MT1 catalyzes one or two methyl transfer reactions on the substrate malonyl-ACP (acyl carrier protein), whereas Co(2+), Fe(2+), Mn(2+), and Ni(2+) support only a single methyl transfer. MT1 homologues exist within the "GNAT" (GCN5-related N-acetyltransferase) loading modules of several modular biosynthetic pathways with propionyl, isobutyryl, or pivaloyl starter units...
November 14, 2017: ACS Chemical Biology
Allegra Leghissa, Zacariah L Hildenbrand, Frank W Foss, Kevin A Schug
Cannabinoids are the primary bioactive constituents of Cannabis sativa and Cannabis indica plants. In this work, gas chromatography in conjunction with triple quadrupole mass spectrometry in multiple reaction monitoring mode was explored for determination of cannabinoids from a surrogate hops matrix. Gas chromatography with mass spectrometry is a reasonable choice for the analysis of these compounds; however, such methods are susceptible to false positives for Δ9-tetrahydrocannabinol, due to decarboxylation of Δ9-tetrahydrocannabinolic acid, its acid precursor, in the hot injection port...
November 2, 2017: Journal of Separation Science
Jae Hwan Kim, Jae Young Kim, Chin Hee Mun, Minah Suh, Jong Eun Lee
Agmatine is a decarboxylated arginine by arginine decarboxylase. Agmatine is known to be a neuroprotective agent. It has been reported that agmatine works as a NMDA receptor blocker or a competitive nitric oxide synthase inhibitor in CNS injuries. In spinal cord injury, agmatine showed reduction of neuropathic pain, improvement of locomotor function, and neuroprotection. Macrophage is a key cellular component in neuroinflammation, a major cause of impairment after spinal cord injury. Macrophage has subtypes, M1 and M2 macrophages...
October 2017: Experimental Neurobiology
Tianfang Ma, Fangxia Zou, Stefan Pusch, Lijun Yang, Qihua Zhu, Yungen Xu, Yueqing Gu, Andreas von Deimling, Xiaoming Zha
Isocitrate dehydrogenases (IDHs) catalyze the oxidative decarboxylation of isocitrate to alpha-ketoglutarate (α-KG) generating carbon dioxide and NADPH/NADH. Evidence suggests that the specific mutations in IDH1 are critical to the growth and reproduction of some tumor cells such as gliomas and acute myeloid leukemia, emerging as an attractive antitumor target. In order to discovery potent new mutant IDH1 inhibitors, we designed, synthesized and evaluated a series of allosteric mIDH1 inhibitors harboring the scaffold of 3-pyrazine-2-yl-oxazolidin-2-ones...
October 13, 2017: Bioorganic & Medicinal Chemistry
Andrés Olmedo, José C Del Río, Jan Kiebist, René Ullrich, Martin Hofrichter, Katrin Scheibner, Angel T Martínez, Ana Gutiérrez
A recently discovered peroxygenase from the fungus Marasmius rotula (MroUPO) is able to catalyze the progressive one-carbon shortening of medium and long-chain mono- and dicarboxylic acids by itself alone, in the presence of H2O2. The mechanism, analyzed using H218O2, starts with an α-oxidation catalyzed by MroUPO generating an α-hydroxy acid, which is further oxidized by the enzyme to a reactive α-keto intermediate whose decarboxylation yields the one-carbon shorter fatty acid. Compared with the previously characterized peroxygenase of Agrocybe aegerita, a wider heme access channel, enabling fatty acid positioning with the carboxylic end near the heme cofactor (as seen in one of the crystal structures available) would be at the origin of the unique ability of MroUPO shortening carboxylic acid chains...
October 30, 2017: Chemistry: a European Journal
Yun Liu, Wenhui Wang, Junwen Han, Jinwei Sun
A copper-promoted cascade decarboxylative halogenation and oxidative diamination reaction sequence of 2-aminopyridines with alkynoic acids has been developed for the synthesis of 2-haloimidazo[1,2-a]pyridines. In this reaction, two C-N bonds and one C-halogen bond are formed in one pot, generating the desired products in good yields. This is the first report on the synthesis of 2-haloimidazo[1,2-a]pyridine derivatives from alkynoic acids.
November 15, 2017: Organic & Biomolecular Chemistry
Małgorzata Pająk, Marianna Kańska
3'-Halotyramines, stereo-selectively labeled with deuterium and tritium, in the (1R) or (1S) position were synthesized using enzymatic methods. The isotopomers labeled in the (1R) position were synthesized by enzymatic decarboxylation of an appropriate 3'-halo-L-tyrosine in deuterated or tritiated incubation medium. The isotopomers labeled in the (1S) position were synthesized by decarboxylation of an appropriate 3'-halo-L-tyrosine, labeled with deuterium or tritium in the α-position of the side chain.
October 16, 2017: Applied Radiation and Isotopes
Antonio F Tiburcio, Rubén Alcázar
The synthesis of spermidine, spermine and thermospermine requires the addition of aminopropyl groups from decarboxylated S-adenosyl-methionine (dSAM). The synthesis of dSAM is catalyzed by S-adenosylmethionine decarboxylase. dSAM levels are usually low, which constitutes a rate-limiting factor in the synthesis of polyamines. In this chapter, we provide a protocol for the determination of SAMDC activity in plants through the detection of radiolabelled CO2 released during the SAMDC reaction.
2018: Methods in Molecular Biology
Rubén Alcázar, Antonio F Tiburcio
In plants, putrescine is synthesized directly from the decarboxylation of ornithine and/or by the alternative arginine decarboxylase pathway. The prevalence of one or the other depends on the tissue and stress conditions. In both amino acid decarboxylation reactions, the corresponding enzymes use pyridoxal phosphate (PLP) as co-factor. PLP combines with the α-amino acid to form a Schiff base, which acts as substrate in the carboxyl group removal and CO2 formation. We describe the methodology employed for the determination of ODC and ADC activities in plant tissues by detecting the release of (C(14)) CO2 using (C(14)) labelled substrates (ornithine or arginine)...
2018: Methods in Molecular Biology
Ryota Hidese, Wakao Fukuda, Masaru Niitsu, Shinsuke Fujiwara
Thermophiles are organisms that grow optimally at temperatures higher than 55 °C. They contain two types of unusual longer/branched-chain polyamines in addition to common polyamines such as spermidine and putrescine. These unusual polyamines contribute to the survival of hyperthermophiles at high temperatures. Recently, the novel aminopropyltransferase BpsA was found to be responsible for the biosynthesis of branched-chain polyamines in the hyperthermophilic archaeon Thermococcus kodakarensis, which contains N (4)-bis(aminopropyl)spermidine as the major polyamine...
2018: Methods in Molecular Biology
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