Zobrazení zdroje stránky Raynormorton3004

Iheyamides A (1), B (2), and C (3), new linear peptides, were isolated from a marine Dapis sp. cyanobacterium. Their structures were elucidated by spectroscopic analyses and degradation reactions. Iheyamide A (1) showed moderate antitrypanosomal activities against Trypanosoma brucei rhodesiense and Trypanosoma brucei brucei (IC50 = 1.5 μM), but the other two analogues, iheyamides B (2) and C (3), did not (IC50 &gt; 20 μM, respectively). The structure-activity relationship clarified that an isopropyl-O-Me-pyrrolinone moiety was necessary for the antitrypanosomal activity. Furthermore, the cytotoxicity of 1 against normal human cells, WI-38, was 10 times weaker than its antitrypanosomal activity (IC50 = 18 μM).An analytical program for multiclass, multiresidue residue analysis to qualitatively and quantitatively determine veterinary drug compounds in game meats by LC-MS/MS has been developed and validated. The method was validated for the analysis of muscle from bison, deer, elk, and rabbit to test for 112 veterinary drug residues from the following drug classes β-agonists, anthelmintics, anti-inflammatory drugs, corticosteroids, fluoroquinolones, β-lactams, macrolides, nitroimidazoles, phenicols, polypeptides, sulfonamides, tetracyclines, thyreostats, and tranquilizers. Muscle was extracted using a simple and quick procedure based on a solvent extraction with 80% ACN/water and sample clean-up with dispersive SPE. The compounds of interest were separated using a Waters HSS T3 column and detected by tandem mass spectrometry with rapid polarity switching to detect both negatively and positively charged ions in a single run. Recoveries were calculated using extracted matrix matched calibration curves for each type of matrix. The average accuracy of fortified compounds ranged from 95.6% to 101% at the target quantitative validation level in the four matrices. The method was also validated as a qualitative screening method where all sample responses were compared to a single extracted-matrix matched calibrant at the target testing level (5 or 25 ng/g). Samples demonstrating a presumptive positive above the threshold value were re-extracted and analyzed with a five-point matrix matching extracted calibration curve. Since the beginning of this survey program, 360 samples have been analyzed for veterinary drug residues in game meats. Antibiotic or tranquilizer residues have been identified in deer (chlortetracycline, haloperidol, and tulathromycin), and rabbit (sulfadiazine).The efficient and stereoselective synthesis of polysubstituted butadienes, especially the multifunctional butadiene, represents a great challenge in organic synthesis. Herein, we wish to report a distinctive Pd(0) car-bene-initiated decarboxylative olefination approach that enables the direct coupling of diazo esters with vinylethylene carbonates (VECs), vinyl oxazolidinones, or vinyl benzoxazinones to afford alcohols, amines, or anilines-containing 1,3-dienes in moderate to high yields and with excellent stereoselectivity. This protocol features operational simplicity, mild reaction conditions, a broad substrate scope, and gram-scalability. Nota-bly, a structurally unique allylic Pd(II) intermediate was isolated and characterized. DFT calculation and control experiments demonstrated that a rare Pd(0) carbene intermediate could be involved in this reaction. Moreover, the polysubstituted butadienes as novel building blocks were unprecedentedly assembled into macrocycles, which efficiently inhibited the P-glycoprotein (P-gp) and dramatically reversed multidrug resistance in cancer cell with 190 folds.Geminal diboronates have attracted significant attention because of their unique structures and reactivity. However, benzo-furan-, indole- and benzothiophene-based benzylic gem-diboronates, building blocks for biologically relevant compounds, are unknown. A promising protocol using visible light and aryl iodides for constructing valuable building blocks, including benzofuran-, indole- and benzothiophene-based benzylic gem-diboronates, via radical carbo-cyclization/gem-diborylation of alkynes with a high functional group tolerance is presented. The utility of these gem-diboronates has been demonstrated by a ten gram scale conversion, by versatile transformations, by including the synthesis of approved drug scaffolds and two approved drugs, and even by polymer synthesis. The mechanistic investigation indicates that the merging of the dinuclear gold catalyst (photoexcitation by 315-400 nm UVA light) with Na2CO3 is directly responsible for photosensitization of aryl iodides (photoexcitation by 254 nm UV light) with blue LEDs light (410-490 nm, λmax = 465 nm) through an energy transfer (EnT) process, followed by homolytic cleavage of the C-I bond in the aryl iodide substrates.A novel method for the generation of uniquely functionalized piperazinones by utilizing post-Ugi functionalization is described. The method involves an Ugi reaction with aminoacetaldehyde dimethyl acetal, followed by acid-mediated cyclization to generate the iminium precursor that was subjected to nucleophilic addition in a diastereoselective manner. The method was also employed to synthesize trans-dragmacidine C and praziquantel-like molecules.The synthesis of the stereotriad core in the eastern portion of the Veratrum alkaloids jervine (1), cyclopamine (2), and veratramine (3) is reported. Starting from a known β-methyltyrosine derivative (8), the route utilizes a diastereoselective substrate-controlled 1,2-reduction to establish the stereochemistry of the vicinal amino alcohol motif embedded within the targets. Oxidative dearomatization is demonstrated to be a viable approach for the synthesis of the spirocyclic DE ring junction found in jervine and cyclopamine.The response in metal concentrations and isotopic composition to variations in photosynthetic activity of aquatic microorganisms is crucially important for understanding the environmental controls on metal fluxes and isotope excursions. [https://www.selleckchem.com/products/ABT-263.html learn more] Here we studied the impacts of two successive diel cycles on physico-chemical parameters, Cu and Zn concentrations and isotopic composition in solution in the presence of mature phototrophic biofilm in a rotating annular bioreactor. The diel cycles induced fluctuations in temperature, pH and dissolved oxygen concentration following the variation in the photosynthesis activity of the biofilm. Diel variations in metal concentrations were primarily related to the pH variation, with an increase in metal concentration in solution related to a pH decrease. For both metals, δ66Zn and δ65Cu in solution exhibited complex but reproducible diel cycles. Diel variations in photosynthetic activity lead to alternatively positive and negative isotope fractionation, producing the sorption of light Zn (Δ66Znsorbed-solution = ‒0.1 ± 0.06 ‰) and heavy Cu isotopes (Δ65Cusorbed-solution = +0.17 ± 0.06 ‰) during the day at high pH and the excretion of Zn light isotopes (‒0.4 less then Δ66Znexcreted-biofilm less then +0.14 ‰) and Cu heavy isotopes (Δ65Cuexcreted-biofilm = +0.7 ± 0.3 ‰) during the night at lower pH. We interpreted Zn and Cu diel cycles as a combination of a desorption of EPS-metal complexes and a small active efflux during the night with an adsorption and an incorporation via an active uptake during the day. The hysteresis of metal concentration in solution over diel cycle suggested the more important role of uptake compared to desorption and efflux from the biofilm. The phototrophic biofilm presents a non-negligible highly labile metal pool with an important potential for contrasting isotopic fractionation at the diel scale.Effective modeling of semivolatile organic chemical (SVOC) partitioning between air and indoor dust is investigated by calculating partition ratios for selected SVOCs between air and n-octanol as well as 8 other oligomers similar in chemical structure to common components of household dust. COSMO-RS solvation theory was used to calculate air-oligomer partition ratios, which were converted to estimates for KOA (octanol-air) and Kdust-air. The results are compared with reported monitored partition ratios with good agreement for the more volatile SVOCs of vapor pressure (VP) exceeding 10-5 Pa and corresponding calculated log Kdust-air (m3 g-1) of less then 5.5 or unitless log KOA of less then 11.5. For less volatile SVOCs, reported values of KDA are significantly lower than predicted, with the deviation increasing with decrease in VP. This effect is attributed to a kinetic delay in which characteristic times for equilibration exceed the dust-air contact time, and equilibrium is not achieved. It is hoped that the approach of computing partition ratios of SVOCs using oligomers selected on the basis of likely dust sources and compositions may improve the estimation of indoor human exposure to SVOCs present in air and dust and assist in exploiting dust samples to monitor and evaluate the fate and exposure of organic chemicals used indoors.We report on the design and synthesis of triscyclometalated iridium (Ir) complexes that contain aryloxy groups at the end of diamino linkers, which exhibit an extraordinarily long-emission lifetime, and were prepared by regioselective substitution reactions of fac-tris-homoleptic cyclometalated Ir complexes, fac-Ir(tpy)3 (tpy = 2-(4'-tolyl)pyridine). It was found that the Ir(tpy)3 complex, equipped with approximately one to six 6-N,N-dimethylamino-2-naphthoic acid (DMANA) groups through the appropriate alkyl linkers, exhibited remarkably long-emission lifetimes of up to 216 μs in DMSO/H2O at room temperature through a reversible electronic energy transfer effect between the Ir complex core and the organic chromophore moieties; however, under the same conditions, the lifetime of fac-Ir(tpy)3 was 1.4 μs. Regarding the mechanistic aspects, the relationship between the emission lifetimes of the Ir complexes and the structures and numbers of the conjugated chromophores, linker lengths, solvents, positions of the chromophores on the Ir(tpy)3 core, and related items are discussed.The behavior of arsenic (As) is usually coupled with iron (Fe) oxide transformation and mediated by both abiotic reactions and microbial processes in the environment. However, quantitative models for the coupled kinetic processes, which specifically consider the arsenate-reducing gene expression correspondent to different reaction conditions, are lacking. In this study, based on the pure cultured Shewanella putrefaciens incubation experiments, extended X-ray absorption fine structure spectroscopy, high resolution transmission electron microscopy, and a suite of microbial analyses, we developed a coupled kinetics model for microbially mediated As reduction and Fe oxide transformation and specifically quantified the As(V) reduction rate coefficients based on the expression patterns of arrA genes. The model reasonably described the temporal changes of As speciation and distribution. The microbial reduction rates of As(V) varied dramatically during the reactions, which were well represented by the varying transcript abundances of arrA genes at different As concentrations. The contributions of biotic and abiotic reactions to the overall reaction rates were assessed. The results improved our quantitative understanding on the key role of As(V)-reducing genes in regulating the speciation and distribution of As. The kinetic modeling approaches based on microbial gene expression patterns are promising for developing comprehensive biogeochemical models of As involving multiple coupled reactions.