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131.
Simone Pilon Steen Ingemann Jørgensen Prof. Dr. Jan H. van Maarseveen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(7):2310-2314
After earlier unsuccessful attempts, this work reports the application of covalent templating for the synthesis of mechanically interlocked molecules (MiMs) bearing no supramolecular recognition sites. Two linear strands were covalently connected in a perpendicular fashion by a central ketal linkage. After subsequent attachment of the first strand to a template via temporary benzylic linkages, the second was linked to the template in a backfolding macrocyclization. The resulting pseudo[1]rotaxane structure was successfully converted to a [2]catenane via a second macrocyclization and cleavage of the ketal and temporary linkages. 相似文献
132.
Mono‐ and Bis(pyrrolo)tetrathiafulvalene Derivatives Tethered to C60: Synthesis,Photophysical Studies,and Self‐Assembled Monolayers 下载免费PDF全文
Dr. Marta Vico Solano Dr. Eduardo Antonio Della Pia Dr. Martyn Jevric Christina Schubert Xintai Wang Dr. Cornelia van der Pol Prof. Dr. Anders Kadziola Prof. Dr. Kasper Nørgaard Prof. Dr. Dirk M. Guldi Prof. Dr. Mogens Brøndsted Nielsen Prof. Dr. Jan O. Jeppesen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(32):9918-9929
A series of mono‐ (MPTTF) and bis(pyrrolo)tetrathiafulvalene (BPTTF) derivatives tethered to one or two C60 moieties was synthesized and characterized. The synthetic strategy for these dumbbell‐shaped compounds was based on a 1,3‐dipolar cycloaddition reaction between aldehyde‐functionalized MPTTF/BPTTF derivatives, two different tailor‐made amino acids, and C60. Electronic communication between the MPTTF/BPTTF units and the C60 moieties was studied by a variety of techniques including cyclic voltammetry and absorption spectroscopy. These solution‐based studies indicated no observable electronic communication between the MPTTF/BPTTF units and the C60 moieties. In addition, femtosecond and nanosecond transient absorption spectroscopy revealed, rather surprisingly, that no charge transfer from the MPTTF/BPTTF units to the C60 moieties takes place on excitation of the fullerene moiety. Finally, it was shown that the MPTTF–C60 and C60–BPTTF‐C60 dyad and triad molecules formed self‐assembled monolayers on a Au(111) surface by anchoring to C60. 相似文献
133.
Synthesis of Oxacyclic Scaffolds via Dual Ruthenium Hydride/Brønsted Acid‐Catalyzed Isomerization/Cyclization of Allylic Ethers 下载免费PDF全文
Dr. Erhad Ascic Ragnhild G. Ohm Dr. Rico Petersen Dr. Mette R. Hansen Casper L. Hansen Daniel Madsen Prof. Dr. David Tanner Prof. Dr. Thomas E. Nielsen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(12):3297-3300
A ruthenium hydride/Brønsted acid‐catalyzed tandem sequence is reported for the synthesis of 1,3,4,9‐tetrahydropyrano[3,4‐b]indoles (THPIs) and related oxacyclic scaffolds. The process was designed on the premise that readily available allylic ethers would undergo sequential isomerization, first to enol ethers (Ru catalysis), then to oxocarbenium ions (Brønsted acid catalysis) amenable to endo cyclization with tethered nucleophiles. This methodology provides not only an attractive alternative to the traditional oxa‐Pictet–Spengler reaction for the synthesis of THPIs, but also convenient access to THPI congeners and other important oxacycles such as acetals. 相似文献
134.
Synthesis of a Natural Product‐Like Compound Collection through Oxidative Cleavage and Cyclization of Linear Peptides 下载免费PDF全文
Dr. Rico Petersen Dr. Sebastian T. Le Quement Prof. Dr. Thomas E. Nielsen 《Angewandte Chemie (International ed. in English)》2014,53(44):11778-11782
Massive efforts in molecular library synthesis have strived for the development of synthesis methodology which systematically delivers natural product‐like compounds of high spatial complexity. Herein, we present a conceptually simple approach that builds on the power of solid‐phase peptide synthesis to assemble precursor peptides (oligomers) designed to undergo oxidative cascade reactions. By harnessing the structural side‐chain diversity and inherent stereochemical features offered by readily available amino acids (monomers), a proof‐of‐concept collection of 54 skeletally and stereochemically diverse compounds was generated, and selected compounds were elaborated into isoform‐selective metalloprotease inhibitors. 相似文献
135.
Alexander Bujotzek Ole Schütt Adam Nielsen Konstantin Fackeldey Marcus Weber 《Journal of mathematical chemistry》2014,52(3):781-804
Obtaining a sufficient sampling of conformational space is a common problem in molecular simulation. We present the implementation of an umbrella-like adaptive sampling approach based on function-based meshless discretization of conformational space that is compatible with state of the art molecular dynamics code and that integrates an eigenvector-based clustering approach for conformational analysis and the computation of inter-conformational transition rates. The approach is applied to three example systems, namely $n$ -pentane, alanine dipeptide, and a small synthetic host-guest system, the latter two including explicitly modeled solvent. 相似文献
136.
Hideyuki Tatsuno Kasper S. Kjr Kristjan Kunnus Tobias C. B. Harlang Cornelia Timm Meiyuan Guo Pavel Chbera Lisa A. Fredin Robert W. Hartsock Marco E. Reinhard Sergey Koroidov Lin Li Amy A. Cordones Olga Gordivska Om Prakash Yizhu Liu Mads G. Laursen Elisa Biasin Frederik B. Hansen Peter Vester Morten Christensen Kristoffer Haldrup Zoltn Nmeth Dorottya Srosin Szemes va Bajnczi Gyrgy Vank Tim B. Van Driel Roberto Alonso‐Mori James M. Glownia Silke Nelson Marcin Sikorski Henrik T. Lemke Dimosthenis Sokaras Sophie E. Canton Asmus O. Dohn Klaus B. Mller Martin M. Nielsen Kelly J. Gaffney Kenneth Wrnmark Villy Sundstrm Petter Persson Jens Uhlig 《Angewandte Chemie (International ed. in English)》2020,59(1):364-372
Iron N‐heterocyclic carbene (NHC) complexes have received a great deal of attention recently because of their growing potential as light sensitizers or photocatalysts. We present a sub‐ps X‐ray spectroscopy study of an FeIINHC complex that identifies and quantifies the states involved in the deactivation cascade after light absorption. Excited molecules relax back to the ground state along two pathways: After population of a hot 3MLCT state, from the initially excited 1MLCT state, 30 % of the molecules undergo ultrafast (150 fs) relaxation to the 3MC state, in competition with vibrational relaxation and cooling to the relaxed 3MLCT state. The relaxed 3MLCT state then decays much more slowly (7.6 ps) to the 3MC state. The 3MC state is rapidly (2.2 ps) deactivated to the ground state. The 5MC state is not involved in the deactivation pathway. The ultrafast partial deactivation of the 3MLCT state constitutes a loss channel from the point of view of photochemical efficiency and highlights the necessity to screen transition‐metal complexes for similar ultrafast decays to optimize photochemical performance. 相似文献
137.
Jacobsen AM Halling-Sørensen B Ingerslev F Hansen SH 《Journal of chromatography. A》2004,1038(1-2):157-170
The veterinary antibacterial agents chlortetracycline (CTC), oxytetracycline (OTC), sulfadiazine (SDZ), erythromycin (ERY) and tylosin (TYL A, B, C and D) were extracted from soil using pressurized liquid extraction (PLE). Citric acid (pH 4.7) and methanol was used as extraction buffer, followed by tandem-solid-phase extraction (SPE) clean-up (SAX + HLB) for all compounds. For quantification two slightly different methods were employed using LC-MS-MS with MRM detection. The soil extraction method was validated using a loamy sand soil and a sandy soil, representing two typical Danish agricultural soils. Recoveries were 50-80% for the tetracyclines (CTC and OTC) and sulfadiazine (SDZ) and 60-100% for the macrolides (TYL and ERY). Limits of detection for the soil extraction method (LOD(soil)) were 0.6-5.6 microg kg(-1) soil for CTC and OTC, 0.9-2.9 microg kg(-1) soil for SDZ and 2.4-5.5 microg kg(-1) soil for TYL A and ERY. Furthermore, the method was applied to field samples taken from two agricultural fields fertilised with liquid manure containing CTC and TYL A. These results showed a decline in the content of antibacterial agents throughout the sampling period of 155 days from 10 to 15 microg CTC kg(-1) soil and 20-55 microg TYL A kg(-1) soil to below or near the LOD(soil) listed above. Finally, the method was applied to barley grains harvested from the fields. None of the antibacterial agents were measured in grain samples, but recoveries for spiked grain samples were similar to soil recoveries. 相似文献
138.
Chakraborty T Holm AI Hvelplund P Nielsen SB Poully JC Worm ES Williams ER 《Journal of the American Society for Mass Spectrometry》2006,17(12):1675-1680
Electron capture by both bare and microsolvated small peptide dications was investigated by colliding these ions with sodium vapor in an accelerator mass spectrometer to provide insight into processes that occur on the microsecond time frame. Survival of the intact peptide monocation after electron capture depends strongly on molecular size. For dipeptides, no intact reduced species were observed; the predominant ions correspond to loss of hydrogen and ammonia. In contrast, the intact reduced species was observed for larger peptides. Calculated structures indicate that the diprotonated dipeptide ions form largely extended structures with low probability of internal ionic hydrogen bonding (i.e., charge solvation) whereas internal ionic H-bonding occurs extensively for larger peptide dications. Solvation of the peptide ions with between one to seven methanol molecules reduces the total extent of H loss even for dipeptides where intact reduced species can survive more than a microsecond after electron capture. The yield of ions corresponding to cleavage of NCalpha bonds (c+ and z+* ions) does not depend strongly on peptide size but decreases with the extent of microsolvation for the dipeptide dications. H-bonding appears to play an important role for the survival of the intact reduced ions but less so for the formation of c+ and z+* ions. Our results indicate that electron capture predominantly occurs at the ammonium groups (at least 70 to 80%), and provides important new insights into the electron capture dissociation process. 相似文献
139.
A laboratory system for the on-line monitoring of important lactic acid fermentation variables is described. The system contains flow-injection analysers for glucose, lactose, galactose, lactate and protein and a continuous-flow analyser for the biomass concentration. The sugar and lactate analysers are based on enzymatic reactions involving oxidases followed by chemiluminescence detection of the hydrogen peroxide formed. The protein analyser is based on the biuret reaction. The system has been used to monitor many fermentation experiments, and some results are presented as examples. 相似文献
140.
Christian Rein Steen Nissen Mariusz Grzelakowski Morten Meldal 《Journal of polymer science. Part A, Polymer chemistry》2016,54(13):2032-2039
A facile click chemistry method of immobilizing surface‐functionalized polymer vesicles on casted polymeric PAN substrates is described. Microporous PAN membranes were subjected to hydrochloric acid hydrolysis to obtain surface carboxylates. The carboxylic groups were activated with EDC/NHS‐solution and were then reacted with propargylamine to introduce alkyne groups for CuAAC reactions. The alkyne functionality of the modified membrane surface was verified by reaction with an azide functional click dye both before and after the immobilization of azide‐functionalized ABA vesicles. The efficient postfunctionalization of the membrane with alkyne allowed quantitative coverage of the membrane surface with a polymersome monolayer, as confirmed by immobilization of polymerzomes loaded with a fluorescent dye. Polymersome monolayers immobilized on alkyne functionalized PAN‐membranes were characterized by cryo‐SEM and monolayers were confirmed by atom force microscopy. These methods opens up new avenues for preparing membrane based filtration and sensor technologies. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2032–2039 相似文献