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991.
992.
Petra Walter Dr. Olaf Hübner Dr. Elisabeth Kaifer Prof. Hans-Jörg Himmel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(46):11943-11956
Proton-coupled electron transfer (PCET) is of key importance in modern synthetic chemistry. Redox-active guanidines were established by our group as valuable alternatives to toxic high-potential benzoquinones in a variety of different PCET reactions. In this work, the PCET reactivity of a series of 1,4-bisguanidino-benzenes varying in their redox potentials and proton affinities is evaluated. The relevant redox and protonation states are fully characterized, and the compounds sorted with respect to their PCET reactivity by comparative PCET experiments supplemented by quantum-chemical calculations. Depending on the studied reactions, the driving force is either electron transfer or proton transfer; thereby the influence of both processes on the overall reactivity could be assessed. Then, two of the PCET reagents are applied in representative oxidative aryl-aryl coupling reactions, namely the intramolecular coupling of 3,3’’-4,4’’-tetramethoxy-o-terphenyl to give the corresponding triphenylene, the intermolecular coupling of N-ethylcarbazole to give N,N’-diethyl-3,3’-bicarbazole, and in the oxidative lactonization of 2-[(4-methoxyphenyl)methyl]-benzoic acid. Under mild conditions, the reactions proceed fast and efficient. Only small amounts of acid are needed, in clear contrast to the corresponding coupling reactions with traditional high-potential benzoquinones such as DDQ or chloranil requiring a large excess of a strong acid. 相似文献
993.
Elisabeth Weyandt Dr. Ivo A. W. Filot Dr. Ghislaine Vantomme Prof. Dr. E. W. Meijer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(37):9700-9707
The correlation between molecular structure and mechanism of supramolecular polymerizations is a topic of great interest, with a special focus on the pathway complexity of porphyrin assemblies. Their cooperative polymerization typically yields highly ordered, long 1D polymers and is driven by a combination of π-stacking due to solvophobic effects and hydrogen bonding interactions. Subtle changes in molecular structure, however, have significant influence on the cooperativity factor and yield different aggregate types (J- versus H-aggregates) of different lengths. In this study, the influence of amide connectivity on the self-assembly behavior of porphyrin-based supramolecular monomers was investigated. While in nonpolar solvents, C=O centered monomers readily assemble into helical supramolecular polymers via a cooperative mechanism, their NH centered counterparts form short, non-helical J-type aggregates via an isodesmic pathway. A combination of spectroscopy and density functional theory modelling sheds light on the molecular origins causing this stunning difference in assembly properties and demonstrates the importance of molecular connectivity in the design of supramolecular systems. Finally, their mutual interference in copolymerization experiments is presented. 相似文献
994.
Jana Hatzfeld Steffen Skowaisa Dr. Elisabeth Jäckel Dr. Julia Kaufmann Prof. Dr. Edgar Haak 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(62):15545-15553
Various triaminocyclopentadienyl ruthenium complexes have been synthesized from Ru3(CO)12. The new complexes were tested for their ability to catalyze cascade conversions of propargyl alcohols. Their associated catalytic activities complement the activities of known diaminocyclopentadienone ruthenium complexes. In particular, the substrate scope of catalytic cycloadditions with 3-ketolactones or phloroglucinol derivatives is extended to terpenoid-derived propargyl alcohols containing an internal alkyne moiety. A wide range of cyclic terpenoid and phloroglucinol adducts are obtained by complementary application of both types of catalysts. 相似文献
995.
Pavel Sidorov Birgit Viira Elisabeth Davioud-Charvet Uko Maran Gilles Marcou Dragos Horvath Alexandre Varnek 《Journal of computer-aided molecular design》2017,31(5):441-451
Generative topographic mapping (GTM) has been used to visualize and analyze the chemical space of antimalarial compounds as well as to build predictive models linking structure of molecules with their antimalarial activity. For this, a database, including ~3000 molecules tested in one or several of 17 anti-Plasmodium activity assessment protocols, has been compiled by assembling experimental data from in-house and ChEMBL databases. GTM classification models built on subsets corresponding to individual bioassays perform similarly to the earlier reported SVM models. Zones preferentially populated by active and inactive molecules, respectively, clearly emerge in the class landscapes supported by the GTM model. Their analysis resulted in identification of privileged structural motifs of potential antimalarial compounds. Projection of marketed antimalarial drugs on this map allowed us to delineate several areas in the chemical space corresponding to different mechanisms of antimalarial activity. This helped us to make a suggestion about the mode of action of the molecules populating these zones. 相似文献
996.
We study the effects of preselection on an expert’s advice about the execution of a project if its execution yields more precise estimates about the expert’s expertise. The introduction of a preselection stage, in which the decision maker evaluates the project before asking for advice, alters the expert’s perception of the problem. We identify conditions under which preselection occurs in equilibrium. We show that if the expert adjusts his behavior, the option to preselect may reduce the expected utility of the decision maker. 相似文献
997.
Elisabeth Remm 《代数通讯》2017,45(7):2956-2966
The notion of breadth of a nilpotent Lie algebra was introduced and used to approach problems of classification up to isomorphism in [5]. In the present paper, we study this invariant in terms of characteristic sequence, another invariant, introduced by Goze and Ancochea in [1]. This permits to complete the determination of Lie algebras of breadth 2 studied in [5] and to begin the work for Lie algebras with breadth greater than 2. 相似文献
998.
One‐Step Synthesis of Collagen Hybrid Gold Nanoparticles and Formation on Egyptian‐like Gold‐Plated Archaeological Ivory
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Dr. Jolanda Spadavecchia Emilande Apchain Marie Albéric Elisabeth Fontan Dr. Ina Reiche 《Angewandte Chemie (International ed. in English)》2014,53(32):8363-8366
A one‐step method is reported to synthesize hybrid gold nanoparticles (AuNPs) by reduction of HAuCl4 in acetic solution in the presence of collagen (Col), dicarboxylic acid‐terminated polyethylene glycol (PEG), and cetyltetrammonium bromide (CTAB) mixed with hydoxyapatite (HAP) as surfactants. Such formation process of AuNPs was shown to be responsible for purple stains naturally formed on Egyptianizing archaeological gilded ivories from 8th BC Syria. The understanding of this formation mechanism, which most likely involves a step with hybrid AuNPs, allows the establishing of an authenticity marker of ancient gold‐plated ivories. 相似文献
999.
Sebastian Letschert Dr. Antonia Göhler Christian Franke Nadja Bertleff‐Zieschang Elisabeth Memmel Priv.‐Doz. Dr. Sören Doose Prof. Dr. Jürgen Seibel Prof. Dr. Markus Sauer 《Angewandte Chemie (International ed. in English)》2014,53(41):10921-10924
Much of the physiology of cells is controlled by the spatial organization of the plasma membrane and the glycosylation patterns of its components, however, studying the distribution, size, and composition of these components remains challenging. A bioorthogonal chemical reporter strategy was used for the efficient and specific labeling of membrane‐associated glycoconjugates with modified monosaccharide precursors and organic fluorophores. Super‐resolution fluorescence imaging was used to visualize plasma membrane glycans with single‐molecule sensitivity. Our results demonstrate a homogeneous distribution of N‐acetylmannosamine (ManNAc)‐, N‐acetylgalactosamine (GalNAc)‐, and O‐linked N‐acetylglucosamine (O‐GlcNAc)‐modified plasma membrane proteins in different cell lines with densities of several million glycans on each cell surface. 相似文献
1000.
Dr. Daniel Franz Dr. Elisabeth Irran Prof. Dr. Shigeyoshi Inoue 《Angewandte Chemie (International ed. in English)》2014,53(51):14264-14268
The reaction of the bulky bis(imidazolin‐2‐iminato) ligand precursor (1,2‐(LMesNH)2‐C2H4)[OTs]2 ( 1 2+ 2[OTs]?; LMes=1,3‐dimesityl imidazolin‐2‐ylidene, OTs=p‐toluenesulfonate) with lithium borohydride yields the boronium dihydride cation (1,2‐(LMesN)2‐C2H4)BH2[OTs] ( 2 + [OTs]?). The boronium cation 2 + [OTs]? reacts with elemental sulfur to give the thioxoborane salt (1,2‐(LMesN)2‐C2H4)BS[OTs] ( 3 + [OTs]?). The hitherto unknown compounds 1 2+ 2[OTs]?, 2 + [OTs]?, and 3 + [OTs]? were fully characterized by spectroscopic methods and single‐crystal X‐ray diffraction. Moreover, DFT calculations were carried out to elucidate the bonding situation in 2 + and 3 +. The theoretical, as well as crystallographic studies reveal that 3 + is the first example for a stable cationic complex of three‐coordinate boron that bears a B?S double bond. 相似文献