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Shu Xian Chong, Yinxue Jin, Steve Chik Fun Au-Yeung, Kenneth Kin Wah To
A series of new platinum Pt(II) compounds possessing a bidentate leaving ligand modified from oxaliplatin has been synthesized, with one of the oxygen ligating atom substituted for a sulphur atom (resulting in a Pt-NNSO coordination core structure). The general structures are R,R-diaminocyclohexane (DACH)-Pt-(methylthio)acetic acid (K4) and DACH-Pt-(thiophenylacetic acid) (K4 derivatives). Substitution of an electron donating or withdrawing group at the ortho or para position on the phenyl ring of K4 derivatives was found to affect the complexes' stability, reactivity with the biological molecules (5'-guanosine monophosphate (5'-GMP) and L-methionine (L-Met)) and anticancer activity...
February 12, 2017: Journal of Inorganic Biochemistry
Youwei Xie, Benjamin List
Herein, we describe the first catalytic asymmetric intramolecular [4+2] cycloaddition of in situ generated ortho-quinone methides. In the presence of a confined chiral imidodiphosphoric acid catalyst, various salicylaldehydes react with dienyl alcohols to give transient ortho-quinone methide intermediates, which undergo an intramolecular [4+2] cycloaddition to provide highly functionalized furanochromanes and pyranochromanes in excellent diastereoselectivity and enantioselectivity.
February 17, 2017: Angewandte Chemie
Markus Neumeyer, Reinhard Brückner
We have accomplished the first total synthesis of an isomerically pure naphthoquinonopyrano-γ-lactone dimer, γ-actinorhodin, in eleven steps. Two steps exploit pairs of peri-MeO groups as unusual selectivity controls. The respective MeO groups convey the steric bulk of a bromo or iodo substituent located ortho to one MeO group as steric hindrance into the vicinity of the second MeO group. This relay effect was indispensable for exerting regiocontrol in an aromatic bromination and diastereocontrol in an oxa-Pictet-Spengler cyclization...
February 17, 2017: Angewandte Chemie
Yang Wang, Vladimir Gevorgyan
A Pd(II) -catalyzed ortho C-H alkoxycarbonylation reaction of aryl silanes toward active hexafluoroisopropyl (HFIP) benzoate esters has been developed. This efficient reaction features high selectivity and good functional-group tolerance. Notably, given the general nature of the silyl-tethered directing group, this method delivers products bearing two independently modifiable sites. NMR studies reveal the presence of hydrogen bonding between HFIP and a pyrimidine nitrogen atom of the directing group, and it is thought to be crucial for the success of this alkoxycarbonylation reaction...
February 17, 2017: Angewandte Chemie
Hosseinagha Aghili, Soghra Yassaei, Neda Joshan, Nemat Hoseini
INTRODUCTION: Coated arch wires and ceramic brackets have been introduced to improve aesthetics during orthodontic treatment. AIM: The aim of this study was to determine the effects of coating on the physical properties of aesthetic orthodontic wires. MATERIAL AND METHODS: Five round wires (0.016 inch) were obtained from each of three brands: conventional uncoated super elastic Nickel Titanium (Ni-Ti) (Rematitian Lite; Dentaurum, Ispringen, Germany), HUBIT (Teflon Coated, Korea), G&H (Epoxy Coated, Greenwood, Indiana, USA) which belonged to maxillary arch...
December 2016: Journal of Clinical and Diagnostic Research: JCDR
Adel M ElSohly, James Irving MacDonald, Nina B Hentzen, Ioana Laura Aanei, Kareem M El Muslemany, Matthew B Francis
The synthesis of complex protein-based bioconjugates has been facilitated greatly by recent developments in chemoselective methods for biomolecular modification. The oxidative coupling of o-aminophenols or catechols with aniline functional groups is chemoselective, mild, and rapid; however, the oxidatively sensitive nature of the electron-rich aromatics and the paucity of commercial sources pose some obstacles to the general use of these reactive strategies. Herein, we identify o-methoxyphenols as air-stable, commercially available derivatives that undergo efficient oxidative couplings with anilines in the presence of periodate as oxidant...
February 16, 2017: Journal of the American Chemical Society
Mauricio Cattaneo, Scott A Ryken, James M Mayer
A diverse set of 2 e(-) /2 H(+) reactions are described that interconvert [Ru(II) (bpy)(en*)2 ](2+) and [Ru(IV) (bpy)(en-H*)2 ](2+) (bpy=2,2'-bipyridine, en*=H2 NCMe2 CMe2 NH2 , en*-H=H2 NCMe2 CMe2 NH(-) ), forming or cleaving different O-H, N-H, S-H, and C-H bonds. The reactions involve quinones, hydrazines, thiols, and 1,3-cyclohexadiene. These proton-coupled electron transfer reactions occur without substrate binding to the ruthenium center, but instead with precursor complex formation by hydrogen bonding...
February 16, 2017: Angewandte Chemie
Nezha Bouhafs, François Lique, Alexandre Faure, Aurore Bacmann, Jun Li, Hua Guo
We present quantum close-coupling calculations for the rotational excitation of the interstellar amidogen radical NH2 due to collisions with H2 molecules. The calculations are based on a recent, high-accuracy full-dimensional NH4 potential energy surface adapted for rigid-rotor scattering calculations. The collisional cross section calculations are performed for all transitions among the first 15 energy levels of both ortho- and para-NH2 and for total energies up to 1500 cm(-1). Both para- and ortho-H2 colliding partners are considered...
February 14, 2017: Journal of Chemical Physics
Isaac Garcia-Bosch, Ryan E Cowley, Daniel E Díaz, Ryan L Peterson, Edward I Solomon, Kenneth D Karlin
Copper-dependent metalloenzymes are widespread throughout metabolic pathways, coupling the reduction of O2 with the oxidation of organic substrates. Small-molecule synthetic analogs are useful platforms to generate L/Cu/O2 species that reproduce the structural, spectroscopic, and reactive properties of some copper-/O2-dependent enzymes. Landmark studies have shown that the conversion between dicopper(II)-peroxo species (L2Cu(II)2(O2(2-)) either side-on peroxo, (S)P, or end-on trans-peroxo, (T)P) and dicopper(III)-bis(μ-oxo) (L2Cu(III)2(O(2-))2: O) can be controlled through ligand design, reaction conditions (temperature, solvent, and counteranion), or substrate coordination...
February 14, 2017: Journal of the American Chemical Society
Agostino Biafora, Bilal A Khan, Janet Bahri, Joachim M Hewer, Lukas J Goossen
A catalyst system composed of [(C6Me6)RuCl2]2, potassium carbonate/guanidine carbonate, and mesitoic acid efficiently promotes the doubly regioselective C-H hydroarylation of unsymmetrical alkynes. The process involves carboxylate-directed ortho-C-H bond activation followed by regioselective addition to the alkyne C-C triple bond with concerted decarboxylation. This action of the carboxylate as a deciduous directing group ensures exclusive monovinylation with high selectivity for the (E)-1,2-diarylalkene.
February 14, 2017: Organic Letters
Zhi-Qiang Ma, Ji-Hong Pan, Da-Xin Jing, Chong-Yan Xu
To observe the biological characteristic and the prognoses in patients with acute erythroleukemia (AEL). The results of 167 patients with newly diagnosed AEL, from January 2004 and June 2014 in the department of Hematology, Shandong Province Chinese Medicine Hospital, were reviewed by morphology, immunology, cytogenetics, molecular biology. Flow cytometry analysis indicated that CD13 (96.1 %), CD33 (95.1 %), CD117 (87.4 %) and CD34 (79.4 %) were highly expressed in AEL. 56 of 148 (37.8 %) AEL patients had a variety of cytogenetic abnormalities, 27 of 148 (18...
March 2017: Indian Journal of Hematology & Blood Transfusion
Maria Elvira Egidia Carbone, James E Castle, Rosanna Ciriello, Anna Maria Salvi, Jon P W Treacy, Peter Zhdan
The electrochemical oxidation of ortho-aminophenol (oAP) by cyclic voltammetry (CV), on platinum substrates in neutral solution, produces a polymeric film (PoAP) that grows to a limiting thickness of about 10 nm. The insulating film has potential use as a bio-immobilizing substrate, its specificity depending on the orientation of its molecular chains. Prior investigations suggest the film consists of alternating quinoneimine and oAP units, progressively filling all the platinum sites during the electrosynthesis...
February 13, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Pamela T Wong, Edward W Roberts, Shengzhuang Tang, Jhindan Mukherjee, Jayme Cannon, Alyssa J Nip, Kaitlin Corbin, Matthew F Krummel, Seok Ki Choi
The use of coumarin caged molecules has been well documented in numerous photocaging applications including for the spatiotemporal control of Cre-estrogen receptor (Cre-ERT2) recombinase activity. In this article, we report that 4-hydroxytamoxifen (4OHT) caged with coumarin via a conventional ether linkage led to an unexpected photo-Claisen rearrangement which significantly competed with the release of free 4OHT. The basis for this unwanted reaction appears to be related to the coumarin structure and its radical-based mechanism of uncaging as it did not occur in ortho-nitrobenzyl (ONB) caged 4OHT that was otherwise linked in the same manner...
February 13, 2017: ACS Chemical Biology
Karishma Mohan, Prashant S Phale
Pseudomonas putida CSV86 degrades lignin-derived metabolic intermediates viz veratrylalcohol, ferulic acid, vanillin and vanillic acid as a sole source of carbon and energy. Strain CSV86 also displayed the ability to degrade lignin sulphonate. Cell respiration, enzyme activity, biotransformation and HPLC analysis suggests that veratyralcohol and ferulic acid are metabolized to vanillic acid by two distinct carbon-source dependent inducible pathways. Vanillic acid was further metabolized to protocatechuic acid and enters the central carbon pathway viaβ-ketoadipate route after ortho ring-cleavage...
February 10, 2017: Applied and Environmental Microbiology
Fernando Rabasa-Alcañiz, Amparo Asensio, María Sánchez-Roselló, Marcos Escolano, Carlos Del Pozo, Santos Fustero
The intramolecular 1,3-dipolar cycloaddition of ortho-substituted 1,1,1-trifluoromethylstyrene-derived nitrones is described. Tricyclic fused isoxazolidines were obtained as major or exclusive products, in contrast to the case for nonfluorinated substrates, which rendered the bridged derivatives. This change in the regioselectivity was attributed to the electronic and, particularly, steric requirements of the trifluoromethyl group in comparison to the methyl group. It is worth mentioning that trifluoromethylstyrenes have been employed for the first time as dipolarophiles in a 1,3-dipolar intramolecular cycloaddition reaction, leading to the corresponding isoxazolidines bearing a quaternary trifluoromethyl moiety...
February 20, 2017: Journal of Organic Chemistry
Kassrin Tangdenpaisal, Kanokpish Chuayboonsong, Somsak Ruchirawat, Poonsakdi Ploypradith
A divergent strategy for the synthesis of the tricyclic 6,7-diaryl-tetrahydro-6H-benzo[c]-chromene core was successfully developed. The 2,3-trans 2,4-cis trisubstituted chroman moiety was formed via a highly efficient and stereoselective Pt(IV)-catalyzed cycloaddition reactions of the corresponding quinone methides with chalcones. Subsequent steps provided the common diene alcohol which underwent BF3.Et2O-mediated Et3SiH reduction and olefin ring-closing metathesis (RCM) using Ru(II) catalysts. The sequence of the final two steps provided a handle to diversify the stereochemical outcomes at C6 as well as C10a...
February 10, 2017: Journal of Organic Chemistry
Jianping Liu, Huan Wang, Shuxia Wang, Qianqian Xue, Dawei Wang, Wang Hang, Huabei Zhang
Fatty acids are myocardial metabolic agent for detecting myocardial ischemia and infraction. However, no (99m) Tc-labeled fatty acids had potential use in clinical practice. In this study, (99m) Tc-CpTT-10-oxo-para-PPA (1d), (99m) Tc-CpTT-11-oxo-para-PPA (2d), (99m) Tc-CpTT-12-oxo-para-PPA (3d), (99m) Tc-CpTT-11-oxo-ortho-PPA (4d) and (99m) Tc-CpTT-11-oxo-meta-PPA (5d) were synthesized by a double ligand transfer reaction, their biological behaviors were investigated. Compound 2d achieved good heart/blood ratio (3...
February 9, 2017: Journal of Labelled Compounds & Radiopharmaceuticals
Nitinkumar Satyadev Upadhyay, Jayachandran Jayakumar, Chien-Hong Cheng
Various substituted indolizidinium, quinolizinium and pyrido[1,2-a]azepinium salts synthesized from benzaldehydes (or α,β-unsaturated aldehydes) and alkyne-amines catalyzed by rhodium complexes via C-H activation are demonstrated. The reaction was carried out under mild reaction conditions using Cu(BF4)2·6H2O as oxidant and anion source and inexpensive oxygen as a co-oxidant. A reaction mechanism involving imine formation followed by an ortho C-H activation, alkyne insertion and reductive elimination via a 7-membered rhodacycle is proposed...
February 10, 2017: Chemical Communications: Chem Comm
Manjula Ravi, Srinivasarao Allu, K C Kumara Swamy
An efficient Rh(III)-catalyzed ortho-alkylation of phenoxy substrates with diazo compounds has been achieved for the first time using pyrimidine or pyridine as the directing group. Furthermore, bis-alkylation has also been achieved using para-substituted phenoxypyrimidine using 3 mole equiv of the diazo ester. The ortho-alkylated derivatives of phenoxy products possessing the ester functionality undergo decarboxylative pyrimidine/pyridine migratory cyclization (rather than deprotection of pyrimidine/pyridine group) using 20% NaOEt in EtOH affording a novel class of 3-(pyrimidin-2(1H)-ylidene)benzofuran-2(3H)-ones and 6-methyl-3-(pyridin-2(1H)-ylidene)benzofuran-2(3H)-one...
February 9, 2017: Journal of Organic Chemistry
Asier Goitia, Enrique Gómez-Bengoa, Arkaitz Correa
Selective bromination reactions of "click compounds" are described. Electron-neutral and electron-deficient arenes selectively undergo unprecedented Pd-catalyzed C-H ortho-halogenations assisted by simple triazoles as modular directing groups, whereas electron-rich arenes are regioselectively halogenated following an electrophilic aromatic substitution reaction pathway. These C-H halogenation procedures exhibit a wide group tolerance, complement existing bromination procedures, and represent versatile synthetic tools of utmost importance for the late-stage diversification of "click compounds"...
February 9, 2017: Organic Letters
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