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881.
Toward Fluorescence‐Based High‐Throughput Screening for Enantiomeric Excess in Amines and Amino Acid Derivatives 下载免费PDF全文
Elena G. Shcherbakova Dr. Valentina Brega Dr. Tsuyoshi Minami Sara Sheykhi Prof. Dr. Tony D. James Prof. Dr. Pavel Anzenbacher Jr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(29):10074-10080
A highly accurate and reliable screening method for enantiomeric excess of amine derivatives in the presence of water is reported. The fluorescence‐based screening system has been realized by self‐assembly of chiral diol‐type dyes (BINOL, VANOL and VAPOL), 2‐formylphenylboronic acid, and chiral amines forming iminoboronate esters. The structure and chirality of the amine analytes determine the stability of the diastereomeric iminoboronate esters, which in turn display differential fluorescence. The fluorescence signal reflects the enantiomeric purity of the chiral amines and was utilized in high‐throughput arrays. The arrays were able to recognize enantiomeric excess of amines, amino esters, and amino alcohols. In addition to qualitative analysis, quantitative experiments were successfully performed. Studies of the role of additives such as water or citrate were carried out to gain insight into the stability of the iminoboronate esters. It is shown that the above additives destabilize less stable esters while the stable esters remain unchanged. Thus, the presence of water and citrate leads to increased difference between the diastereomeric iminoboronates and contributes to the enantiodiscrimination of the chiral amines. 相似文献
882.
883.
Bis‐clickable Mesoporous Silica Nanoparticles: Straightforward Preparation of Light‐Actuated Nanomachines for Controlled Drug Delivery with Active Targeting 下载免费PDF全文
Dr. Achraf Noureddine Dr. Magali Gary‐Bobo Dr. Laure Lichon Dr. Marcel Garcia Prof. Jeffrey I. Zink Dr. Michel Wong Chi Man Dr. Xavier Cattoën 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(28):9624-9630
Bis(clickable) mesoporous silica nanospheres (ca. 100 nm) were obtained by the co‐condensation of TEOS with variable amounts (2–5 % each) of two clickable organosilanes in the presence of CTAB. Such nanoparticles could be easily functionalized with two independent functions using the copper‐catalyzed alkyne‐azide cycloaddition (CuAAC) reaction to transform them into nanomachines bearing cancer cell targeting ligands with the ability to deliver drugs on‐demand. The active targeting was made possible after anchoring folic acid by CuAAC click reaction, whereas the controlled delivery was performed by clicked azobenzene fragments. Indeed, the azobenzene groups are able to obstruct the pores of the nanoparticles in the dark whereas upon irradiation in the UV or in the blue range, their trans‐to‐cis photoisomerization provokes disorder in the pores, enabling the delivery of the cargo molecules. The on‐command delivery was proven in solution by dye release experiments, and in vitro by doxorubicin delivery. The added value of the folic acid ligand was clearly evidenced by the difference of cell killing induced by doxorubicin‐loaded nanoparticles under blue irradiation, depending on whether the particles featured the clicked folic acid ligand or not. 相似文献
884.
Andreas Uwe Meyer Karolína Straková Dr. Tomáš Slanina Prof. Dr. Burkhard König 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(25):8694-8699
Alkyl‐ and aryl vinyl sulfones were obtained by eosin Y (EY)‐mediated visible‐light photooxidation of sulfinate salts and the reaction of the resulting S‐centered radicals with alkenes. Optimized reaction conditions, the sulfinate and alkene scope, and X‐ray structural analyses of several reaction products are provided. A detailed spectroscopic study explains the reaction mechanism, which proceeds through the EY radical cation as key intermediate oxidizing the sulfinate salts. 相似文献
885.
Florence Malmedy Prof. Dr. Thomas Wirth 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(45):16072-16077
The first stereoselective version of an iodine(III)‐mediated rearrangement of arylketones in the presence of orthoesters is described. The reaction products, α‐arylated esters, are very useful intermediates in the synthesis of bioactive compounds such as ibuprofen. With chiral lactic acid‐based iodine(III) reagents product selectivities of up to 73 % ee have been achieved. 相似文献
886.
Dr. Yungen Liu Dr. Chun-Wai Tse Dr. Kar-Yee Lam Dr. Xiao-Yong Chang Dr. Xiangguo Guan Meng-Yao Chao Dr. Jie-Sheng Huang Prof. Dr. Chi-Ming Che 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(46):10828-10833
Ruthenium(II) complexes bearing a tridentate bis(N-heterocyclic carbene) ligand reacted with iminoiodanes (PhI=NR) resulting in the formation of isolable ruthenium(III)–amido intermediates, which underwent cleavage of a C−N bond of the tridentate ligand and formation of an N-substituted imine group. The RuIII–amido intermediates have been characterized by 1H NMR, UV/Vis, ESI-MS, and X-ray crystallography. DFT calculations were performed to provide insight into the reaction mechanism. 相似文献
887.
Madeleine A. Dallaston Christian J. Bettencourt Dr. Sharon Chow Joshua Gebhardt Jordan Spangler Dr. Martin R. Johnston Craig Wall Dr. Jason S. Brusnahan Prof. Craig M. Williams 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(41):9614-9618
Common oxidants used in chemical synthesis, including newly developed perruthenates, were evaluated in the context of understanding (and better appreciating) the sensitiveness and associated potential hazards of these reagents. Analysis using sealed cell differential scanning calorimetry (scDSC) facilitated Yoshida correlations, which were compared to impact sensitiveness and electrostatic discharge experiments (ESD), that enabled sensitiveness ranking. Methyltriphenylphoshonium perruthenate (MTP3, 8 ), isoamyltriphenylphosphonium perruthenate (ATP3, 7 ) and tetraphenylphosphonium perruthenate (TP3, 9 ) were found to be the most sensitive followed by 2-iodoxybenzoic acid (IBX, 2 ) and benzoyl peroxide (BPO, 10 ), whereas the most benign were observed to be Oxone ( 12 ), manganese dioxide (MnO2, 13 ), and N-bromosuccinimide (NBS, 17 ). 相似文献
888.
Paul M. Bogie Lauren R. Holloway Courtney Ngai Tabitha F. Miller Divine K. Grewal Prof. Richard J. Hooley 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(43):10232-10238
A self-assembled Fe4L6 cage complex internally decorated with acid functions is capable of accelerating the thioetherification of activated alcohols, ethers and amines by up to 1000-fold. No product inhibition is seen, and effective supramolecular catalysis can occur with as little as 5 % cage. The substrates are bound in the host with up to micromolar affinities, whereas the products show binding that is an order of magnitude weaker. Most importantly, the cage host alters the molecularity of the reaction: whereas the reaction catalyzed by simple acids is a unimolecular, SN1-type substitution process, the rate of the host-mediated process is dependent on the concentration of nucleophile. The molecularity of the cage-catalyzed reaction is substrate-dependent, and can be up to bimolecular. In addition, the catalysis can be prevented by a large excess of nucleophile, where substrate inhibition dominates, and the use of tritylated anilines as substrates causes a negative feedback loop, whereby the liberated product destroys the catalyst and stops the reaction. 相似文献
889.
Yandong Dou Kenry Dr. Jiang Liu Jianze Jiang Prof. Qing Zhu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(28):6896-6901
o-Alkenylation of unprotected phenols has been developed by direct C−H functionalization catalyzed by PdII. This work features phenol group as a directing group and realizes highly site-selective C−H bond functionalization of phenols to achieve the corresponding products in moderate to excellent yields at 60 °C. The advantages of this reaction include unprecedented C−H functionalization using phenol as a directing group, high regioselectivity, good substrate scope, mild reaction conditions, and high efficiency. To the best of our knowledge, this is the first example of a regioselective C−H alkenylation of unprotected phenols utilizing phenolic hydroxyl group as a directing group. The alkenylation of unprotected tyrosine and intramolecular cyclization are also successfully carried out under this catalytic system in good yields. Furthermore, this novel method enables a late-stage modification of complex phenol-containing bioactive molecules toward a diversity-oriented drug discovery. 相似文献
890.
Cytochrome P450 119 Compounds I Formed by Chemical Oxidation and Photooxidation Are the Same Species
Dr. Zhi Su Dr. John H. Horner Prof. Dr. Martin Newcomb 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(61):14015-14020
Compound I from cytochrome P450 119 prepared by the photooxidation method involving peroxynitrite oxidation of the resting enzyme to Compound II followed by photooxidation to Compound I was compared to Compound I generated by m-chloroperoxybenzoic acid (MCPBA) oxidation of the resting enzyme. The two methods gave the same UV/Visible spectra, the same products from oxidations of lauric acid and palmitic acid and their (ω-2,ω-2,ω-3,ω-3)-tetradeuterated analogues, and the same kinetics for oxidations of lauric acid and caprylic acid. The experimental identities between the transients produced by the two methods leave no doubt that the same Compound I species is formed by the two methods. 相似文献