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https://www.readbyqxmd.com/read/30118152/synthesis-and-properties-of-networks-based-on-thiol-ene-chemistry-using-a-co-2-based-%C3%AE-lactone
#1
Lifeng Chen, Jun Ling, Xufeng Ni, Zhiquan Shen
3-Ethylidene-6-vinyltetrahydro-2H-pyran-2-one, a divinyl δ-lactone derived from CO2 and 1,3-butadiene, is used for the synthesis of networks with various compositions through the thiol-ene click reaction with di- and tri-thiol compounds. Thermal, mechanical, and optical properties of the networks are characterized. The networks have sharp and uniform glass transitions and show good thermal stability with T d from 287 to 332 °C. Mechanical properties of the networks can be adjusted by the cross-link density; 6...
August 17, 2018: Macromolecular Rapid Communications
https://www.readbyqxmd.com/read/30111790/cooperative-asymmetric-reactions-combining-photocatalysis-and-enzymatic-catalysis
#2
Zachary C Litman, Yajie Wang, Huimin Zhao, John F Hartwig
Living organisms rely on simultaneous reactions catalysed by mutually compatible and selective enzymes to synthesize complex natural products and other metabolites. To combine the advantages of these biological systems with the reactivity of artificial chemical catalysts, chemists have devised sequential, concurrent, and cooperative chemoenzymatic reactions that combine enzymatic and artificial catalysts1-9 . Cooperative chemoenzymatic reactions consist of interconnected processes that generate products in yields and selectivities that cannot be obtained when the two reactions are carried out sequentially with their respective substrates2,7 ...
August 2018: Nature
https://www.readbyqxmd.com/read/30110492/a-facile-synthesis-of-cysteine-based-diketopiperazine-from-thiol-protected-precursor
#3
Di Zhang, Wayne Wang
l-Cysteine is one of the most promising biomass-based building blocks with great potential applications. Herein, we report a versatile synthetic route to produce cysteine-based 2,5-diketopiperazine (DKP) with good yield from the thiol-ene click reaction of l-cysteine and commercially available acrylates, followed by dimerization of the amino acid intermediates. The achieved DKP diastereomers were successfully separated and fully characterized by spectroscopic methods. Moreover, the chiroptical property of DKP in the presence of various metal ions was investigated by circular dichroism spectroscopy...
June 2018: Royal Society Open Science
https://www.readbyqxmd.com/read/30102822/rh-catalyzed-4-2-1-cycloaddition-of-in-situ-generated-ene-yne-ene-allenes-and-co
#4
Zhixiang Yu
We report here the first Rh-catalyzed [4+2+1] cycloaddition of in situ generated ene/yne-ene-allenes and CO to synthesize challenging seven-membered carbocycles fused with five-membered rings. This reaction is designed based on the 1,3-acyloxy migration of ene/yne-ene-propargyl esters to ene/yne-ene-allenes, followed by oxidative cyclization, CO insertion and reductive elimination to form the final [4+2+1] cycloadducts. The possible competing [4+1], [4+2] and [2+2+1] cycloadditions were disfavored, making the present reaction as an efficient way to access functionalized 5/7 rings...
August 13, 2018: Angewandte Chemie
https://www.readbyqxmd.com/read/30087920/ene-reaction-of-nitrosocarbonyl-mesitylene-with-the-cinnamyl-alcohol-metabolic-activity-and-apoptosis-of-the-synthetized-6-chloropurine-n-o-nucleoside-analogues
#5
Misal Giuseppe Memeo, Elena Valletta, Beatrice Macchi, Alessio Porta, Bruna Bovio, Mattia Moiola, Paolo Quadrelli
Nitrosocarbonyl mesitylene intermediate undergoes an ene reaction with cinnamyl alcohol affording the corresponding 5-hydroxy-isoxazolidine in fair yields. The synthesized 5-acetoxy-isoxazolidine serves as synthon for the preparation of 6-chloropurine N,O-nucleoside analogues, according to the Vorbrüggen reaction. The compounds were evaluated for their metabolic and apoptotic activity, and their structure-activity relationship is discussed.
July 31, 2018: ACS Omega
https://www.readbyqxmd.com/read/30087911/chemical-recycling-of-poly-bisphenol-a-carbonate-by-glycolysis-under-1-8-diazabicyclo-5-4-0-undec-7-ene-catalysis
#6
Eugenio Quaranta, Clara Castiglione Minischetti, Giuseppe Tartaro
The glycolysis reaction of poly(bisphenol A carbonate) (PC) has been explored under 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) catalysis as a potential route to valorize PC wastes by chemical recycling. The amidine base is an active catalyst of PC glycolysis and, under suitable conditions, promotes effectively and selectively the depolymerization of the polymeric material with 1,2-propanediol or glycerol to give the monomer bisphenol A (BPA) and the relevant cyclic carbonate. The depolymerization process has been investigated under solventless conditions, using diol/triol as the reagent and reaction medium, and also in an auxiliary solvent such as tetrahydrofuran (THF) that is able to dissolve the polymer...
July 31, 2018: ACS Omega
https://www.readbyqxmd.com/read/30086947/a-novel-one-pot-strategy-to-prepare-%C3%AE-cyclodextrin-functionalized-capillary-monoliths-for-enantioseparation-of-basic-drugs
#7
Miaoduo Deng, Meng Li, Yu Zhao, Zhen Jiang, Xingjie Guo
With native β-cyclodextrin (β-CD) added into the polymerization mixture directly, a novel, convenient and low-cost one-pot strategy was developed to prepare the β-CD functionalized organic polymer monolithic capillary column. Diazabicyclo[5.4.0]undec-7-ene (DBU) as a basic catalyst for the ring opening reaction between β-CD and glycidyl methacrylate (GMA) was introduced into the polymerization system for the first time. Thereby, two consecutive reactions namely the in situ methacrylation of β-CD and copolymerization reaction can be achieved in one pot...
November 1, 2018: Talanta
https://www.readbyqxmd.com/read/30086625/zwitterionic-crosslinked-biodegradable-nanocapsules-for-cancer-imaging
#8
Haotian Sun, Lingyue Yan, Kevin A Carter, Jiaqi Zhang, Julia Caserto, Jonathan F Lovell, Yun Wu, Chong Cheng
Zwitterionic crosslinked biodegradable nanocapsules (NCs) were synthesized for cancer imaging. A polylactide (PLA)-based diblock copolymer with two blocks carrying acetylenyl and allyl groups respectively was synthesized by ring-opening polymerization (ROP). Azide-alkyne "click" reaction was conducted to conjugate sulfobetaine (SB) zwitterions and fluorescent dye Cy5.5 onto the acetylenyl-functionalized first block of the diblock copolymer. The resulting copolymer with a hydrophilic SB/Cy5.5-functionalized PLA block and a hydrophobic allyl-functionalized PLA block could stabilize miniemulsions because of its amphiphilic diblock structure...
August 7, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/30082884/the-energy-transfer-enabled-biocompatible-disulfide-ene-reaction
#9
Michael Teders, Christian Henkel, Lea Anhäuser, Felix Strieth-Kalthoff, Adrián Gómez-Suárez, Roman Kleinmans, Axel Kahnt, Andrea Rentmeister, Dirk Guldi, Frank Glorius
Sulfur-containing molecules participate in many essential biological processes. Of utmost importance is the methylthioether moiety, present in the proteinogenic amino acid methionine and installed in tRNA by radical-S-adenosylmethionine methylthiotransferases. Although the thiol-ene reaction for carbon-sulfur bond formation has found widespread applications in materials or medicinal science, a biocompatible chemo- and regioselective hydrothiolation of unactivated alkenes and alkynes remains elusive. Here, we describe the design of a general chemoselective anti-Markovnikov hydroalkyl/aryl thiolation of alkenes and alkynes-also allowing the biologically important hydromethylthiolation-by triplet-triplet energy transfer activation of disulfides...
August 6, 2018: Nature Chemistry
https://www.readbyqxmd.com/read/30081637/intramolecular-tandem-seleno-michael-aldol-reaction-a-simple-route-to-hydroxy-cyclo-1-ene-1-carboxylate-esters
#10
Piotr Banachowicz, Jacek Mlynarski, Szymon Buda
Intramolecular tandem seleno-Michael/aldol reaction followed by oxidation-elimination process can be an efficient tool for the construction of hydroxy cyclo-1-ene-1-carboxylate esters from oxo-α,β-unsaturated esters. Generation of lithium selenolate from elemental selenium and n-BuLi provides a simple and efficient one-pot access to cyclic endo-Morita-Baylis-Hillman adducts.
August 6, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/30078968/association-of-intercellular-adhesion-gene-a-with-biofilm-formation-in-staphylococci-isolates-from-patients-with-conjunctivitis
#11
Taghreed H T Elkhashab, Lamiaa A Adel, Mona Saad Nour, Magda Mahran, Mai Elkaffas
BACKGROUND: There is a great negative impact of biofilm-mediated infection on patient health which necessitates the use of reliable methods for detecting biofilm producers. AIMS: This study was done to determine biofilm-producing ability and the presence of intercellular a dhesion g ene A in clinical staphylococcal isolates and to assess the reliability of two phenotypic methods used for biofilm detection. MATERIALS AND METHODS: Fifty staphylococcal strains were isolated from 100 conjunctival swabs from patients attended the Ophthalmology Outpatient Department of the Research Institute of Ophthalmology...
July 2018: Journal of Laboratory Physicians
https://www.readbyqxmd.com/read/30075068/rhodium-catalyzed-tandem-addition-cyclization-rearrangement-of-alkynylhydrazones-with-organoboronic-acids
#12
Kyoungmin Choi, Hoyoon Park, Chulbom Lee
Transition metal-mediated catalysis routinely enables substrates of multiple π-systems to be efficiently coupled with various carbon nucleophiles along with simultaneous ring formation. This transformation, however, remains unexplored in connection with pericyclic processes. Reported here is a protocol for cycloalkene synthesis based on the merger of rhodium catalysis and a retro-ene reaction. The approach allows alkyne-tethered hydrazones and organoboronic acids to undergo a cascade of addition-cyclization-rearrangement reactions to provide cycloalkene products...
August 9, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/30074286/2-allyl-and-propargylamino-datps-for-site-specific-enzymatic-introduction-of-a-single-modification-in-minor-groove-of-dna
#13
Jan Matyasovsky, Radek Pohl, Michal Hocek
A series of 2-alkylamino-2'-deoxyadenosine triphosphates (dATP) was prepared and found to be substrates for the Therminator DNA polymerase which incorporated only one modified nucleotide into the primer. Using a template encoding for two consecutive adenines, we found conditions for incorporation of either one or two modified nucleotides. In all cases, addition of a mixture of natural dNTPs led to primer extension resulting in site-specific single modification of DNA in the minor groove. The allylamino-substituted DNA was used for the thiol-ene addition whereas the propargylamino- DNA for the CuAAC click reaction to label the DNA with a fluorescent dye in the minor groove...
August 3, 2018: Chemistry: a European Journal
https://www.readbyqxmd.com/read/30073515/digital-microfluidic-immobilized-cytochrome-p450-reactors-with-integrated-inkjet-printed-microheaters-for-droplet-based-drug-metabolism-research
#14
Gowtham Sathyanarayanan, Markus Haapala, Iiro Kiiski, Tiina Sikanen
We report the development and characterization of digital microfluidic (DMF) immobilized enzyme reactors (IMERs) for studying cytochrome P450 (CYP)-mediated drug metabolism on droplet scale. The on-chip IMERs consist of porous polymer (thiol-ene) monolith plugs prepared in situ by photopolymerization and functionalized with recombinant CYP1A1 isoforms (an important detoxification route for many drugs and other xenobiotics). The DMF devices also incorporate inexpensive, inkjet-printed microheaters for on-demand regio-specific heating of the IMERs to physiological temperature, which is crucial for maintaining the activity of the temperature-sensitive CYP reaction...
August 2, 2018: Analytical and Bioanalytical Chemistry
https://www.readbyqxmd.com/read/30065226/a-molecular-electron-density-theory-study-of-the-competitiveness-of-polar-diels%C3%A2-alder-and-polar-alder-ene-reactions
#15
Luis R Domingo, Mar Ríos-Gutiérrez, Patricia Pérez
The competitiveness of the BF₃ Lewis acid (LA) catalyzed polar Diels⁻Alder (P-DA) and polar Alder-ene (P-AE) reactions of 2-methyl-1,3-butadiene, a diene possessing an allylic hydrogen, with formaldehyde has been studied within the Molecular Electron Density Theory (MEDT) at the MPWB1K/6-311G(d,p) computational level. Coordination of BF₃ LA to the oxygen of formaldehyde drastically accelerates both reactions given the high electrophilic character of the BF₃:formaldehyde complex. As a consequence, these reactions present a very low activation enthalpy-less than 2...
July 31, 2018: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/30062120/a-reversible-and-repeatable-thiol-ene-bioconjugation-for-dynamic-patterning-of-signaling-proteins-in-hydrogels
#16
Joseph C Grim, Tobin E Brown, Brian A Aguado, Douglas A Chapnick, Alexandrea L Viert, Xuedong Liu, Kristi S Anseth
Biomolecule-functionalized hydrogels have emerged as valuable cell culture platforms to recapitulate the mechanical and biochemical properties of the extracellular niche. The typical strategy to functionalize hydrogels with biomolecules involves directly tethering them to the hydrogel backbone resulting in a static material. Thus, this approach fails to capture the dynamic changes in biomolecule composition that occur during biological processes or that may be required for regenerative medicine applications...
July 25, 2018: ACS Central Science
https://www.readbyqxmd.com/read/30043009/dynamic-kinetic-asymmetric-transformations-of-%C3%AE-halo-%C3%AE-keto-esters-by-n-n-dioxide-ni-ii-catalyzed-carbonyl-ene-reaction
#17
Wen Liu, Weidi Cao, Haipeng Hu, Lili Lin, Xiaoming Feng
Dynamic kinetic asymmetric transformations of racemic β-halo-α-keto esters through carbonyl-ene reaction were realized using a chiral N,N'-dioxide-nickel(ii) complex, giving the corresponding β-halo-α-hydroxy esters containing two vicinal chiral tri- and tetrasubstituted carbon centers in good yields and dr with excellent ee values without the use of extra bases. Meanwhile, a proposed reaction mechanism was presented according to the configuration of the product.
August 7, 2018: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/30040138/self-healing-polycaprolactone-networks-through-thermo-induced-reversible-disulfide-bond-formation
#18
Liangdong Zhang, Teng Qiu, Zhiqiang Zhu, Longhai Guo, Xiaoyu Li
Polycaprolactone (PCL) networks with disulfide bonds are synthesized through a thiol-ene "click" reaction. The PCL networks have various functional properties, including self-healing, shape memory, reprocessability, and degradability. Pronouncedly, a healing efficiency of 92% on the yield strength of the PCL network is obtained after heating for 1 h at 60 °C. Meanwhile, the PCL networks show shape memory property with fixing ratio (R f ) and recovery ratio (R r ) at 98% and 95%, respectively. The PCL network still retains good mechanical properties after reprocessing cycles and can be fast-decomposed through a thiol-disulfide exchange reaction...
July 24, 2018: Macromolecular Rapid Communications
https://www.readbyqxmd.com/read/30033732/metal-free-annulation-at-the-ortho-and-bay-positions-of-perylene-bisimide-leading-to-lateral-%C3%AF-extension-with-strong-nir-absorption
#19
Ramprasad Regar, Ruchika Mishra, Pradip Kumar Mondal, Jeyaraman Sankar
A novel ortho/ bay annulation reaction of perylene bisimide (PBI) has been explored in a single step synthetic procedure using perylene bisimide 1 and 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU) in the absence of any metal catalyst. The single crystal solid-state X-ray diffraction structure showed a distorted framework of DBU-fused PBI 2. Compound 2 exhibited intense near-infrared absorption up to 950 nm. Reversible protonation and deprotonation accompany drastic changes in the photophysical characteristics. Further, the reaction of perylene biscarboxyanhydride with DBU offered a caprolactam ring-substituted perylene bisimide 3...
August 3, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/30033296/a-novel-thiol-ene-click-reaction-for-preparation-of-graphene-quantum-dots-and-their-potential-for-fluorescence-imaging
#20
Hongye Huang, Meiying Liu, Xun Tuo, Junyu Chen, Liucheng Mao, Yuanqing Wen, Jianwen Tian, Naigen Zhou, Xiaoyong Zhang, Yen Wei
Graphene quantum dots (GQDs), as a kind of carbon dots with the structure of graphene, possess fascinating properties of both carbon dots and graphene have attracted increasing attention for various applications especially in the biomedical fields. It is therefore, many methods for preparation of GQDs have been developed over the last decade. However, most of the previous reports are required tedious experimental procedure and hazardous agents. In this study, we developed an unparalleled preparation method for preparation of GQDs from graphene oxide through a one-step thiol-ene click reaction...
October 1, 2018: Materials Science & Engineering. C, Materials for Biological Applications
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