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https://read.qxmd.com/read/30870550/selective-amidation-by-a-photocatalyzed-umpolung-reaction
#1
Debasish Ghosh, Rajesh Nandi, Saikat Khamarui, Sukla Ghosh, Dilip K Maiti
A metal-catalyzed organic transformation merged with another organophotocatalyst has been developed under mild conditions for production of α-ketoamides. CuI-catalyzed highly selective and rapid COCH2-amidation in the presence of electrophilic Cα[double bond, length as m-dash]O bonds, which is synchronized by an eosin Y (EY)-photocatalyst, furnishes a wide range of labile α-ketoamides, unsymmetrical oxalamides and chiral analogues on the treatment of 1,3-dicarbonyls with amines, PhIO and LED light at room temperature...
March 14, 2019: Chemical Communications: Chem Comm
https://read.qxmd.com/read/30869516/diastereoselective-abb-three-component-synthesis-of-highly-functionalized-spirooxindoles-bearing-five-consecutive-asymmetric-carbons
#2
Thavaraj Vivekanand, B S Vachan, Muthu Karuppasamy, Isravel Muthukrishnan, C Uma Maheswari, Subbiah Nagarajan, Nattamai Bhuvanesh, Vellaisamy Sridharan
The synthesis of spirooxindoles bearing tetrahydro-4H-cyclopenta[b]furan framework was established starting from isatin-derived aldehydes and two equivalents of 1,3-dicarbonyl compounds involving a piperidine-catalyzed ABB' three-component domino process. This reaction was highly diastereoselective affording a single diastereomer of spirooxindoles with five consecutive asymmetric carbons including a spiro and tetrasubstituted carbon centers. In addition, this waste-free (-2H2O) reaction showed high atom- and step economy by creating four new bonds including three C-C and one C-O bonds, and two rings (one carbo- and one heterocycle) in a single operation...
March 14, 2019: Journal of Organic Chemistry
https://read.qxmd.com/read/30866163/total-synthesis-of-cephalotaxine-and-homoharringtonine-via-furan-oxidation-transannular-mannich-cyclization
#3
Xuan Ju, Christopher Beaudry
Homoharringtonine and its precursor, cephalotaxine, were synthesized. Oxidative ring-opening of a furan unveils a amine-tethered dicarbonyl, which undergoes spontaneous transannular Mannich cyclization. The cascade builds the full cephalotaxine substructure in a single operation in 60% yield. A Noyori reduction enabled synthesis of the title compounds with excellent eantioselectivity (krel = 278).
March 13, 2019: Angewandte Chemie
https://read.qxmd.com/read/30843127/regioselective-synthesis-of-pyrimidine-fused-tetrahydropyridines-and-pyridines-by-microwave-assisted-one-pot-reaction
#4
Pooja Kumari, Rahul Yadav, Ruchi Bharti, Tasneem Parvin
A regioselective three-component reaction of α,β-unsaturated aldehydes, cyclic 1,3-dicarbonyls and 6-aminouracils in the presence of FeCl3 ·6H2 O as catalyst under microwave irradiation has been demonstrated. Three-component reaction of α,β-unsaturated aldehydes like cinnamaldehyde/crotonaldehyde, cyclic 1,3-diketones such as 2-hydroxy-1,4-naphthaquinone/dimedone and 6-aminouracils provides regioselective pyrimidine-fused tetrahydropyridines tethered with cyclic 1,3-diketones. On the other hand, replacing cyclic 1,3-diketones by 4-hydroxycoumarin and keeping all other conditions the same provided a two-component pyrimidine-fused pyridines...
March 7, 2019: Molecular Diversity
https://read.qxmd.com/read/30821972/co-displacement-in-an-oxidative-addition-of-primary-silanes-to-rhodium-i
#5
Abhranil Biswas, Arkady Ellern, Aaron D Sadow
The rhodium dicarbonyl {PhB(OxMe2 )2 ImMes }Rh(CO)2 (1) and primary silanes react by oxidative addition of a nonpolar Si-H bond and, uniquely, a thermal dissociation of CO. These reactions are reversible, and kinetic measurements model the approach to equilibrium. Thus, 1 and RSiH3 react by oxidative addition at room temperature in the dark, even in CO-saturated solutions. The oxidative addition reaction is first-order in both 1 and RSiH3 , with rate constants for oxidative addition of PhSiH3 and PhSiD3 revealing kH / kD ∼ 1...
March 1, 2019: Inorganic Chemistry
https://read.qxmd.com/read/30820329/a-systematic-review-the-appraisal-of-the-effects-of-metformin-on-lipoprotein-modification-and-function
#6
REVIEW
K G Kheniser, S R Kashyap, T Kasumov
Aims: Metformin is a commonly prescribed anti-hyperglycaemic pharmacological agent, and it remains a staple in the management of type II diabetes. In addition to metformin's glucose lowering effects, research has indicated that metformin inhibits glycation-mediated and oxidative modification of lipoprotein residues. The purpose was to discuss the effects of metformin as it relates to high-density lipoprotein (HDL) and low-density lipoprotein (LDL) modification. Materials and methods: The purpose was to conduct a narrative and pragmatic review on the effects of metformin as it pertains to HDL and LDL modification...
February 2019: Obesity Science & Practice
https://read.qxmd.com/read/30807156/domino-self-sensitized-photooxygenation-of-conjugated-dienones-for-the-synthesis-of-1-2-4-trioxanes
#7
Martin Jorge Riveira, Nadia L Martiren, Mirta P Mischne
The photochemical behavior of several dienones was studied under aerobic conditions. 2-Allylidene-1,3-cycloalkanediones prepared via Knoevenagel-type condensation between simple readily available 1,3-dicarbonyl substrates and α,β-unsaturated aldehydes, afforded 1,2,4-trioxane derivatives upon UVA-irradiation in the presence of oxygen. This domino self-sensitized photooxygenation cascade of conjugated carbonyl systems proceeds stereoselectively and involves the formation of two new oxa-cycles, three new bonds (two C-O) and three stereocenters...
February 26, 2019: Journal of Organic Chemistry
https://read.qxmd.com/read/30793908/divergent-c-h-oxidative-radical-functionalization-of-olefins-to-install-tertiary-alkyl-motifs-enabled-by-copper-catalysis
#8
Ming-Qing Tian, Cong Wang, Xu-Hong Hu, Teck-Peng Loh
An efficient tertiary alkylation reaction of olefins with 1,3-dicarbonyl compounds was developed by virtue of copper catalyst without the use of expensive ligands or additives. In contrast to alkyl Heck-type reaction, alkyl halide is not required. Notably, by varying the nitrogen and air atmosphere, the reaction selectively produces alkylation and alkylation-oxygenation products, respectively. Initial investigations revealed that an α-carbonyl alkyl radical species might be involved in the process.
February 22, 2019: Organic Letters
https://read.qxmd.com/read/30781346/antiglycative-activity-and-rage-expression-in-rett-syndrome
#9
Valeria Cordone, Alessandra Pecorelli, Mascia Benedusi, Silvano Santini, Stefano Falone, Joussef Hayek, Fernanda Amicarelli, Giuseppe Valacchi
Rett syndrome (RTT) is a human neurodevelopmental disorder, whose pathogenesis has been linked to both oxidative stress and subclinical inflammatory status (OxInflammation). Methylglyoxal (MG), a glycolytic by-product with cytotoxic and pro-oxidant power, is the major precursor in vivo of advanced glycation end products (AGEs), which are known to exert their detrimental effect via receptor- (e.g., RAGE) or non-receptor-mediated mechanisms in several neurological diseases. On this basis, we aimed to compare fibroblasts from healthy subjects (CTR) with fibroblasts from RTT patients (N = 6 per group), by evaluating gene/protein expression patterns, and enzymatic activities of glyoxalases (GLOs), along with the levels of MG-dependent damage in both basal and MG-challenged conditions...
February 15, 2019: Cells
https://read.qxmd.com/read/30777425/formal-4-2-annulation-of-oxindole-embedded-ortho-quinone-methides-with-1-3-dicarbonyls-synthesis-of-spiro-chromen-4-3%C3%A2-oxindole-scaffolds
#10
Yao-Bin Shen, Shuai-Shuai Li, Yun-Ming Sun, Xicheng Liu, Liping Yu, Qing Liu, Jian Xiao
The oxindole-embedded ortho-quinone methides, in situ generated from oxindole-embedded ortho-hydroxybenzyl alcohols, were employed as reactive intermediates in formal [4 + 2] annulation with 1,3-dicarbonyls, providing an efficient access to spiro[chromen-4,3´-oxindole] scaffolds via a cascade conjugate addition/ketalization/dehydration process. This protocol featured metal-free conditions, wide substrate scope and excellent yields.
February 19, 2019: Journal of Organic Chemistry
https://read.qxmd.com/read/30771486/sirt1-participates-in-the-response-to-methylglyoxal-dependent-glycative-stress-in-mouse-oocytes-and-ovary
#11
Giovanna Di Emidio, Silvano Junior Santini, Anna Maria D'Alessandro, Antonella Vetuschi, Roberta Sferra, Paolo Giovanni Artini, Gaspare Carta, Stefano Falone, Fernanda Amicarelli, Carla Tatone
Methylglyoxal (MG), a highly reactive dicarbonyl derived from metabolic processes, is the most powerful precursor of advanced glycation end products (AGEs). Glycative stress has been recently associated with ovarian dysfunctions in aging and PCOS syndrome. We have investigated the role of the NAD+ -dependent Class III deacetylase SIRT1 in the adaptive response to MG in mouse oocytes and ovary. In mouse oocytes, MG induced up-expression of glyoxalase 1 (Glo1) and glyoxalase 2 (Glo2) genes, components of the main MG detoxification system, whereas inhibition of SIRT1 by Ex527 or sirtinol reduced this response...
February 13, 2019: Biochimica et Biophysica Acta. Molecular Basis of Disease
https://read.qxmd.com/read/30758887/cu-catalyzed-4-1-annulation-toward-indolo-2-1-a-isoquinolines-via-oxidative-c-sp3-c-sp2-h-bond-bifunctionalization
#12
Bo Jiang, Tian-Shu Zhang, Qi Zhao, Wen-Juan Hao, Shu-Jiang Tu
A new Cu-catalyzed [4 + 1] annulation of N-aryl-1,2,3,4-tetrahydroisoquinolines (N-aryl THIQs) with α-diazoketones has been established under oxidative conditions, leading to the construction of a series of indolo[2,1-a]isoquinolines with generally good yields. The reaction enables dediazotized dicarbonylation of α-diazoketones, making direct C(sp3)/C(sp2)-H bond bifunctionalization to access tetracyclic aza-heterocyclic skeletons.
February 13, 2019: Chemistry, An Asian Journal
https://read.qxmd.com/read/30732783/characterization-of-polysaccharide-fractions-from-fruit-of-actinidia-arguta-and-assessment-of-their-antioxidant-and-antiglycated-activities
#13
Rugang Zhu, Xinyu Zhang, Yu Wang, Lijiao Zhang, Jing Zhao, Gang Chen, Jungang Fan, Youfeng Jia, Fengwen Yan, Chong Ning
A novel cell-wall polysaccharides (AAPs) were extracted from the fruits of Actinidia arguta and separated into four parts which were named water-eluted polysaccharide (WPS), salt-eluted polysaccharide (SPS)-1, SPS-2 and SPS-3. The monosaccharide composition and structural analysis showed that SPS-3 and SPS-2 were homogalacturonan (HG)-rich pectin, SPS-1 was rhamnogalacturonan (RG)-rich pectin and WPS was starch-like polysaccharides. All four kinds of polysaccharides displayed the ability to scavenge free radicals, chelate iron ion, inhibit lipid peroxidation and inhibit protein glycation, but SPS was obviously stronger than WPS...
April 15, 2019: Carbohydrate Polymers
https://read.qxmd.com/read/30724971/visible-light-induced-consecutive-c-c-bond-fragmentation-and-formation-for-the-synthesis-of-elusive-unsymmetric-1-8-dicarbonyl-compounds
#14
Meishan Ji, Zhen Wu, Chen Zhu
Synthesis of the valuable unsymmetric 1,8-dicarbonyl compounds remains underexplored currently. Herein, we disclose a new strategy for the synthesis of 1,8-diketones through the coupling of cyclopropanols and cyanohydrins under visible-light irradiation. The protocol features a cascade of intriguing ring opening of cyclopropanols and remote cyano migration. The unfavorable addition of an alkyl radical to an electron-rich alkene is facilitated by the intramolecular cyanohydrin interception. A variety of multiply functionalized 1,8-diketones are furnished in useful yields...
February 6, 2019: Chemical Communications: Chem Comm
https://read.qxmd.com/read/30698966/oh-initiated-oxidation-of-imidazoles-in-tropospheric-aqueous-phase-chemistry
#15
Tamara Felber, Thomas Schaefer, Hartmut Herrmann
Imidazoles formed via the reaction of dicarbonyls with nitrogen containing compounds in the atmospheric particle-phase can be expected to initiate secondary organic aerosol (SOA) growth due to their potential to act as photosensitizers. Recent field studies quantified imidazoles for the first time in ambient aerosol samples from Europe and China. However, the knowledge about the kinetics and mechanisms of particle-phase reactions involving imidazoles is still very limited. In the present study, the radical-driven aqueous-phase oxidative degradation reactions of the hydroxyl radical (●OH) with imidazoles were investigated...
January 30, 2019: Journal of Physical Chemistry. A
https://read.qxmd.com/read/30694064/enantioselective-radical-hydroacylation-of-enals-with-%C3%AE-ketoacids-enabled-by-photoredox-amine-cocatalysis
#16
Jia-Jia Zhao, Hong-Hao Zhang, Xu Shen, Shouyun Yu
A photoredox/amine-cocatalyzed enantioselective radical hydroacylation of enals with α-ketoacids is described. Acyl radicals generated from α-ketoacids act as the acylation reagent with the iminium ions. This strategy provides an efficient way to access synthetically challenging 1,4-dicarbonyl compounds in an enantioselective manner. The reactions of various enals with α-ketoacids show the generality and limitations of this method.
January 29, 2019: Organic Letters
https://read.qxmd.com/read/30679389/the-antitumor-drug-lb-100-is-a-catalytic-inhibitor-of-protein-phosphatase-2a-ppp2ca-and-5-ppp5c-coordinating-with-the-catalytic-metals-in-the-active-site-of-pp5c
#17
Brandon M D'Arcy, Mark R Swingle, Cinta Maria Papke, Kevin A Abney, Erin S Bouska, Aishwarya Prakash, Richard E Honkanen
LB-100 is an experimental cancer-therapeutic with cytotoxic activity against cancer cells in culture and antitumor activity in animals. The first Phase I trial (NCT01837667) evaluating LB-100 recently concluded that safety and efficacy parameters are favorable for further clinical testing. Although LB-100 is widely reported as a specific inhibitor of serine/threonine phosphatase 2A (PP2AC/PPP2CA:PPP2CB), we could find no experimental evidence in the published literature demonstrating the specific engagement of LB-100 with PP2A in vitro, in cultured cells, or in animals...
January 24, 2019: Molecular Cancer Therapeutics
https://read.qxmd.com/read/30674353/methylglyoxal-a-glycolysis-metabolite-triggers-metastasis-through-mek-erk-smad1-pathway-activation-in-breast-cancer
#18
Marie-Julie Nokin, Justine Bellier, Florence Durieux, Olivier Peulen, Gilles Rademaker, Maude Gabriel, Christine Monseur, Benoit Charloteaux, Lieven Verbeke, Steven van Laere, Patrick Roncarati, Michael Herfs, Charles Lambert, Jean Scheijen, Casper Schalkwijk, Alain Colige, Jo Caers, Philippe Delvenne, Andrei Turtoi, Vincent Castronovo, Akeila Bellahcène
BACKGROUND: Elevated aerobic glycolysis rate is a biochemical alteration associated with malignant transformation and cancer progression. This metabolic shift unavoidably generates methylglyoxal (MG), a potent inducer of dicarbonyl stress through the formation of advanced glycation end products (AGEs). We have previously shown that the silencing of glyoxalase 1 (GLO1), the main MG detoxifying enzyme, generates endogenous dicarbonyl stress resulting in enhanced growth and metastasis in vivo...
January 23, 2019: Breast Cancer Research: BCR
https://read.qxmd.com/read/30667228/copper-catalyzed-oxidative-sp3-carbon-radical-cross-coupling-with-trialkylphosphites-leading-to-%C3%AE-phosphonyl-1-3-dicarbonyl-compounds
#19
Jian-Ping Zou, Cheng-Kun Li, Ze-Kun Tao, Zhi-Hao Zhou, Xiaoguang Bao, Shao-Fang Zhou
A copper-catalyzed radical Csp3-H/P(OR)3 cross-coupling reaction for the formation of Csp3-P bonds is described. A range of 1,3-dicarbonyl compounds and trialkylphosphites were coupled in this fashion to give the corresponding products in moderate to good yields. This protocol provides direct access to α-phosphonyl 1,3-dicarbonyl compounds.
January 22, 2019: Journal of Organic Chemistry
https://read.qxmd.com/read/30661613/molecular-structure-regulation-and-enzyme-cascade-signal-amplification-strategy-for-upconversion-ratiometric-luminescent-and-colorimetric-alkaline-phosphatase-detection
#20
Hongyu Chen, Zile Zhou, Qiujun Lu, Cuiyan Wu, Meiling Liu, Youyu Zhang, Shouzhuo Yao
Herein, molecular structure regulation and enzyme cascade signals amplification (MRECAmp) strategy was proposed to construct a novel upconversion ratiometric fluorescence and colorimetric dual-readout assay platform for highly sensitive and selective detection of alkaline phosphatase (ALP) activity. The detection strategy is divided into three aspects. Firstly, Ag+ oxidates o-phenylenediamine (OPD) to 2,3-diaminophennazine (OPDox), which can significantly quench upconversion fluorescence at 487 nm based on inner filter effects (IFE) while the upconversion emission at 668 nm was essentially unchanged for Zn2+ -doped NaYF4 :Yb3+ ,Er3+ ,Tm3+ upconversion nanoparticles (UCNPs) probes under the near-infrared (NIR) irradiation...
March 21, 2019: Analytica Chimica Acta
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