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981.
Back Cover: Quantum Mechanics/Molecular Mechanics Study on the Oxygen Binding and Substrate Hydroxylation Step in AlkB Repair Enzymes (Chem. Eur. J. 2/2014) 下载免费PDF全文
982.
Synthesis and Conformational Analysis of Cyclic Homooligomers from Pyranoid ε‐Sugar Amino Acids 下载免费PDF全文
Dr. Andrés Feher‐Voelger Jorge Borges‐González Dr. Romen Carrillo Dr. Ezequiel Q. Morales Dr. Javier González‐Platas Dr. Tomás Martín 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(14):4007-4022
New pyranoid ε‐sugar amino acids were designed as building blocks, in which the carboxylic acid and the amine groups were placed in positions C2 and C3 with respect to the tetrahydropyran oxygen atom. By using standard solution‐phase coupling procedures, cyclic homooligomers containing pyranoid ε‐sugar amino acids were synthesized. Conformation analysis was performed by using NMR spectroscopic experiments, FTIR spectroscopic studies, X‐ray analysis, and a theoretical conformation search. These studies reveal that the presence of a methoxy group in the position C4 of the pyran ring produces an important structural change in the cyclodipeptides. When the methoxy groups are present, the structure collapses through interresidue hydrogen bonds between the oxygen atoms of the pyran ring and the amide protons. However, when the cyclodipeptide lacks the methoxy groups, a U‐shape structure is adopted, in which there is a hydrophilic concave face with four oxygen atoms and two amide protons directed toward the center of the cavity. Additionally, we found important evidence of the key role played by weak electrostatic interactions, such as the five‐membered hydrogen‐bonded pseudocycles (C5) between the amide protons and the ether oxygen atoms, in the conformation equilibrium of the macrocycles and in the cyclization step of the cyclic tetrapeptides. 相似文献
983.
Cover Picture: Molecular Origin of the Hydrolytic Activity and Fixed Regioselectivity of a ZrIV‐Substituted Polyoxotungstate as Artificial Protease (Chem. Eur. J. 31/2014) 下载免费PDF全文
984.
Back Cover: Synthesis,Characterization, Self‐Assembly,Gelation, Morphology and Computational Studies of Alkynylgold(III) Complexes of 2,6‐Bis(benzimidazol‐2′‐yl)pyridine Derivatives (Chem. Eur. J. 32/2014) 下载免费PDF全文
985.
Inside Cover: New Concepts for Designing d10‐M(L)n Catalysts: d Regime,s Regime and Intrinsic Bite‐Angle Flexibility (Chem. Eur. J. 36/2014) 下载免费PDF全文
986.
987.
High‐Yield Formation of Substituted Tetracyanobutadienes from Reaction of Ynamides with Tetracyanoethylene 下载免费PDF全文
Dr. Marie Betou Nicolas Kerisit Esme Meledje Dr. Yann R. Leroux Dr. Claudine Katan Dr. Jean‐François Halet Dr. Jean‐Claude Guillemin Dr. Yann Trolez 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(31):9553-9557
A high‐yielding sequence of [2+2] cycloaddition–retroelectrocyclization of ynamides with tetracyanoethylene (TCNE) is described. The reaction provided tetracyanobutadiene (TCBD) species, which were characterized by various techniques. DFT and TD‐DFT calculations were also performed to complement experimental findings. 相似文献
988.
Platinum Complexes Containing Pyramidalized Germanium and Tin Dihalide Ligands Bound through σ,σ ME Multiple Bonds 下载免费PDF全文
Florian Hupp Dr. Mengtao Ma Franziska Kroll Dr. J. Oscar C. Jimenez‐Halla Dr. Rian D. Dewhurst Dr. Krzysztof Radacki Dr. Andreas Stasch Prof. Dr. Cameron Jones Prof. Dr. Holger Braunschweig 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(51):16888-16898
We present the isolation of the first mononuclear dihalogermylene, and mono‐ and dinuclear stannylene complexes of transition metals. These exhibit exceptionally pyramidalized Group 14 centers. Additionally, removal of the halide substituents from the Ge/Sn atom was successfully performed in two ways, halide abstraction and reduction, leading to a variety of unusual structural motifs. 相似文献
989.
Dr. Luke D. Elliott Dr. Jonathan P. Knowles Dr. Paul J. Koovits Katie G. Maskill Michael J. Ralph Dr. Guillaume Lejeune Lee J. Edwards Richard I. Robinson Ian R. Clemens Brian Cox David D. Pascoe Guido Koch Martin Eberle Malcolm B. Berry Prof. Kevin I. Booker‐Milburn 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(46):15226-15232
The use of flow photochemistry and its apparent superiority over batch has been reported by a number of groups in recent years. To rigorously determine whether flow does indeed have an advantage over batch, a broad range of synthetic photochemical transformations were optimized in both reactor modes and their yields and productivities compared. Surprisingly, yields were essentially identical in all comparative cases. Even more revealing was the observation that the productivity of flow reactors varied very little to that of their batch counterparts when the key reaction parameters were matched. Those with a single layer of fluorinated ethylene propylene (FEP) had an average productivity 20 % lower than that of batch, whereas three‐layer reactors were 20 % more productive. Finally, the utility of flow chemistry was demonstrated in the scale‐up of the ring‐opening reaction of a potentially explosive [1.1.1] propellane with butane‐2,3‐dione. 相似文献
990.
Dramatic Influence of an Anionic Donor on the Oxygen‐Atom Transfer Reactivity of a MnV–Oxo Complex 下载免费PDF全文
Heather M. Neu Dr. Matthew G. Quesne Tzuhsiung Yang Dr. Katharine A. Prokop‐Prigge Prof. Kyle M. Lancaster James Donohoe Prof. Serena DeBeer Dr. Sam P. de Visser Prof. David P. Goldberg 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(45):14584-14588
Addition of an anionic donor to an MnV(O) porphyrinoid complex causes a dramatic increase in 2‐electron oxygen‐atom‐transfer (OAT) chemistry. The 6‐coordinate [MnV(O)(TBP8Cz)(CN)]? was generated from addition of Bu4N+CN? to the 5‐coordinate MnV(O) precursor. The cyanide‐ligated complex was characterized for the first time by Mn K‐edge X‐ray absorption spectroscopy (XAS) and gives Mn?O=1.53 Å, Mn?CN=2.21 Å. In combination with computational studies these distances were shown to correlate with a singlet ground state. Reaction of the CN? complex with thioethers results in OAT to give the corresponding sulfoxide and a 2e?‐reduced MnIII(CN)? complex. Kinetic measurements reveal a dramatic rate enhancement for OAT of approximately 24 000‐fold versus the same reaction for the parent 5‐coordinate complex. An Eyring analysis gives ΔH≠=14 kcal mol?1, ΔS≠=?10 cal mol?1 K?1. Computational studies fully support the structures, spin states, and relative reactivity of the 5‐ and 6‐coordinate MnV(O) complexes. 相似文献