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71.
Lynn Vanhaecke Lieven Van MeulebroekNathalie De Clercq Julie Vanden Bussche 《Analytica chimica acta》2013
A prominent trend which has been observed in recent years in the analysis of veterinary drugs and growth-promoting agents is the shift from target-oriented procedures, mainly based on liquid chromatography coupled to triple-quadrupole mass spectrometry (LC-QqQ-MS), towards accurate mass full scan MS (such as time of flight (ToF) and Fourier Transform (FT) Orbitrap MS). In this study the applicability of high resolution single-stage-Orbitrap-MS for confirmatory analysis of growth-promoting agents in meat was compared to that of a QqQ-MS. Validation according to CD 2002/657/EC demonstrated that steroid analysis based on Orbitrap MS, operating at a resolution of 50,000 FWHM, is indeed capable to compete with QqQ-MS in terms of selectivity/specificity, while providing excellent linearity (for most compounds >0.99) but somewhat inferior sensitivity. Indeed, CCαs reached from 0.04–0.88 μg kg−1 for the 34 anabolic steroids upon MS/MS detection, while upon Orbitrap MS detection a range of 0.07–2.50 μg kg−1 was observed. Using QqQ-MS adequate precision was obtained since relative standard deviations, associated with the repeatability and intra-laboratory reproducibility, were below 20%. In the case of Orbitrap MS, for some compounds (i.e. some estrogens) this threshold was exceeded and thus poor precision was observed, which is possibly caused by the lack in sensitivity. Overall, it may be concluded that Orbitrap-MS offers an adequate performance in terms of linearity and precision but lacks in sensitivity for some of the compounds. 相似文献
72.
A reliable method for direct synthesis of β‐dichlorosubstituted acetanilides is reported. The key transformation involves the oxidative and catalytic cleavage of a carbon‐carbon bond in the presence of iodine trichloride (ICl3). In this protocol ICl3 is used not only as the catalyst but also as the oxidant which widely broadens the scope of its application in organic synthetic chemistry. 相似文献
73.
Phthalimide derivatives as nitrogen nucleophiles with α,β‐unsaturated aldehydes for asymmetric aza‐Michael additions have been reported. The reactions proceed smoothly to afford corresponding Michael adducts in good yields (up to 98%) and enantioselectivities (up to 95% ee). 相似文献
74.
Yu-Huan Geng Dr. Yuan-Zhao Hua Dr. Shi-Kun Jia Prof. Dr. Min-Can Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(16):5130-5135
The first regio-, diastereo-, and enantioselective direct Mannich reaction of β,γ,-unsaturated ketones with benzoxazinone cyclic imines was enabled by Lewis acid/Brønsted base cooperative catalysis. The dinuclear zinc complex catalyzed the reaction of a broad range of β,γ-unsaturated ketones to proceed at the α-site exclusively, leading to corresponding adducts with two consecutive tertiary carbon stereocenters in diastereomeric ratios of up to >20:1 and enantioselectivities generally in the 90–99 % ee range. These products were used as general intermediates in the synthesis of multisubstituted cyclocanalines, tetrahydro pyridazinones, and 4H-furo[2,3-b][1,4]benzoxazine derivatives. 相似文献
75.
Dr. Saida Majdoub Dr. Zoltán Garda Alexandre C. Oliveira Dr. Inga Relich Agnès Pallier Dr. Sara Lacerda Dr. Christelle Hureau Dr. Carlos F. G. C. Geraldes Dr. Jean-François Morfin Dr. Éva Tóth 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(6):2009-2020
Metal chelates targeted to amyloid peptides are widely explored as diagnostic tools or therapeutic agents. The attachment of a metal complex to amyloid recognition units typically leads to a decrease in peptide affinity. We show here that by separating a macrocyclic GdL chelate and a PiB targeting unit with a long hydrophobic C10 linker, it is possible to attain nanomolar affinities for both Aβ1-40 (Kd=4.4 nm ) and amylin (Kd=4.5 nm ), implicated, respectively in Alzheimer's disease and diabetes. The Scatchard analysis of surface plasmon resonance data obtained for a series of amphiphilic, PiB derivative GdL complexes indicate that their Aβ1-40 or amylin binding affinity varies with their concentration, thus micellar aggregation state. The GdL chelates also affect peptide aggregation kinetics, as probed by thioflavin-T fluorescence assays. A 2D NMR study allowed identifying that the hydrophilic region of Aβ1-40 is involved in the interaction between the monomer peptide and the Gd3+ complex. Finally, ex vivo biodistribution experiments were conducted in healthy mice by using 111In labeled analogues. Their pancreatic uptake, ∼3 %ID g−1, is promising to envisage amylin imaging in diabetic animals. 相似文献
76.
Dr. Subhabrata Chaudhury Dr. Penchala Narasimharao Meka Dr. Monimoy Banerjee Caitlin N. Kent Prof. Dr. Brian S. J. Blagg 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(59):14747-14764
The 90 kDa heat shock proteins (Hsp90) are molecular chaperones that are responsible for the folding and/or trafficking of ∼400 client proteins, many of which are directly associated with cancer progression. Consequently, inhibition of Hsp90 can exhibit similar activity as combination therapy as multiple signaling nodes can be targeted simultaneously. In fact, seventeen small-molecule inhibitors that bind the Hsp90 N-terminus entered clinical trials for the treatment of cancer, all of which exhibited pan-inhibitory activity against all four Hsp90 isoforms. Unfortunately, most demonstrated undesired effects alongside induction of the pro-survival heat shock response. As a result, isoform-selective inhibitors have been sought to overcome these detriments. Described herein is a structure-based approach to design Hsp90β-selective inhibitors along with preliminary SAR. In the end, compound 5 was shown to manifest ∼370-fold selectivity for Hsp90β versus Hsp90α, and induced the degradation of select Hsp90β-dependent clients. These data support the development of Hsp90β-selective inhibitors as a new paradigm to overcome the detriments associated with pan-inhibition of Hsp90. 相似文献
77.
Christian A. Malapit Donald R. Caldwell Irungu K. Luvaga Dr. Jonathan T. Reeves Dr. Ivan Volchkov Dr. Nina C. Gonnella Dr. Zhengxu S. Han Dr. Carl A. Busacca Prof. Dr. Amy R. Howell Dr. Chris H. Senanayake 《Angewandte Chemie (International ed. in English)》2017,56(24):6999-7002
β-Ketonitriles bearing a quaternary carbon at the 2-position were prepared through Rh-catalyzed addition of aryl boronic acids to 2,2-disubstituted malononitriles. In contrast to the previously described transnitrilative cyanation of aryl boronic acids with dialkylmalononitriles, the present reaction avoids retro-Thorpe collapse of the intermediate addition product through the use of a milder base. The reaction was amenable to a variety of aryl boronic acids and disubstituted malononitriles, providing a diverse array of β-ketonitriles. The products could be further derivatized to valuable chiral α,α-disubstituted-β-aminonitriles through addition reactions to the corresponding N-tert-butanesulfinyl imines. 相似文献
78.
This communication describes a convenient synthesis of fused bicyclic pyrazolones in a one-pot reaction procedure. Modified protocols are also developed to access 5,5-bicyclic and bulky pyrazolones in good yields. The method reported herein represents a practical approach to structurally diversified bicyclic pyrazolones. 相似文献
79.
Jihen Mahfoudh Christelle Delaite Souhir Abid Rachid El Gharbi 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(12):1002-1008
A series of random polyesteramides (PEAs) within a range of molar composition from 90/10 to 10/90 were synthesized by a direct melt polycondensation of lactic acid and β-alanine. Their structures were fully characterized by NMR spectroscopy. The resulting copolymers are amorphous; they are thermally stable to temperatures up to 254°C, and present increasing glass transition temperatures at increasing amide content. The copolymers were also characterized by FTIR and viscosimetry measurements. 相似文献
80.
Abstract Novel moni-β-lactams derived from esters of amino acids have been prepared in one step by the high pressure promoted [2 + 2] cycloaddition of enol ethers with isocyanates derived from esters of amino acids. The effect of substituents in the enol ether and in the isocyanate on the scope of the synthesis has been demonstrated. 相似文献