共查询到20条相似文献,搜索用时 15 毫秒
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Bo Qin Sheng Shen Chang Sun Dr. Zhiyun Du Prof. Dr. Kun Zhang Dr. Huaqiang Zeng 《化学:亚洲杂志》2011,6(12):3298-3305
POCl3‐mediated one‐pot macrocyclization allows the highly selective formation of five‐residue macrocycles that are rigidified by internally placed intramolecular hydrogen bonds. Mechanistic investigation by using tailored competition experiments and kinetic simulation provides a comprehensive model, supporting a chain‐growth mechanism underlying the one‐pot formation of aromatic pentamers, whereby the successive addition of a bifunctional monomer unit onto either another monomer or the growing oligomeric backbone is faster than other types of bimolecular condensations involving oligomers longer than monomers. DFT calculations at the B3LYP/6‐31G* level reveal the five‐residue pentamer to be the most stable with respect to alternative four‐, six‐, and seven‐residue macrocycles. These novel mechanistic insights may become useful in analyzing other macrocyclization, oligomerization, and ploymerization reactions. 相似文献
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Xiao‐Na Xu Lu Wang Gui‐Tao Wang Jian‐Bin Lin Guang‐Yu Li Dr. Xi‐Kui Jiang Prof. Dr. Zhan‐Ting Li Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(23):5763-5774
Dynamic covalent synthesis! Intramolecular hydrogen‐bonding induces amino‐ and aldehyde‐appended aryl amides to adopt a rigid “V”‐shaped conformation. As a result, stable two‐layered capsules can be assembled quantitatively through the one‐step formation of six imine bonds. The new capsules form complexes with aliphatic diammonium ions to give unique two‐layered pseudo[3]rotaxanes (see figure).
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Dr. Peter Schweyen Martin Hoffmann Jens Krumsieck Dr. Benedikt Wolfram Dr. Xiulan Xie Prof. Dr. Martin Bröring 《Angewandte Chemie (International ed. in English)》2016,55(34):10118-10121
Zinc and cadmium complexes of meso‐arylisoporphyrins carrying a pyrrolyl or dipyrrinyl substituent at the sp3 carbon atom were obtained through a simple one‐pot variation of the Alder–Longo porphyrin synthesis. Key to the formation and stabilization of isoporphyrins is the presence of metal acetates during the oxidative macrocyclization step. The characteristic Q‐bands of isoporphyrins are found in the NIR region between 750 nm and 880 nm. All of the isolated pyrrolyl‐ and dipyrrinyl‐appended isoporphyrins are stable under typical laboratory conditions and allow chemical transformations like BF2 coordination, transmetalation, and ligand exchange. 相似文献
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Tetrathiafulvalene‐Based Macrocycles Formed by Radical Cation Dimerization: The Role of Intramolecular Hydrogen Bonding and Solvent 下载免费PDF全文
Wei‐Kun Wang Yuan‐Yuan Chen Dr. Hui Wang Prof. Dr. Dan‐Wei Zhang Prof. Dr. Yi Liu Prof. Dr. Zhan‐Ting Li 《化学:亚洲杂志》2014,9(4):1039-1044
Compounds 1 a and 1 b were prepared by appending two tetrathiafulvalene (TTF) units to an aromatic amide segment that is driven by six or two intramolecular N? H???O hydrogen bonds to adopt a folded conformation. UV/Vis absorption experiments revealed that if the TTF units were oxidized to TTF.+ radical cations, the two compounds could form a stable single molecular noncovalent macrocycle in less polar dichloromethane or dichloroethane or a bimolecular noncovalent macrocycle in a binary mixture of dichloromethane with a more polar solvent owing to remarkably enhanced dimerization of the TTF.+ units. The stability of the (TTF.+)2 dimer was evaluated through UV/Vis absorption, electron paramagnetic resonance, and cyclic voltammetry experiments and also by comparing the results with those of control compound 2 . The results showed that introduction of the intramolecular hydrogen bonds played a crucial role in promoting the stability of the (TTF.+)2 dimer and thus the noncovalent macrocyclization of the two backbones in both uni‐ and bimolecular manners. 相似文献
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Sascha S. Zhu Dipl.‐Chem. Martin Nieger Dr. Jörg Daniels Dr. Thorsten Felder Dr. Iordan Kossev Dr. Thomas Schmidt Dr. Moritz Sokolowski Prof. Dr. Fritz Vögtle Prof. Dr. Christoph A. Schalley Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(20):5040-5046
Flexible rigidity : Tetralactam macrocycles of the Hunter type bear a rigid scaffold (see space‐filling representation), but can still widely adapt to the properties of a guest molecule inside their cavities. X‐ray crystal structures of a series of differently substituted macrocycles reveal a remarkably broad variety of intermolecular hydrogen‐bonding patterns organizing the macrocycles in the crystals in intriguingly different ways.
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Dr. Hajime Abe Tetsuhiro Yoneda Dr. Yuki Ohishi Prof. Dr. Masahiko Inouye 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(52):18944-18952
Hexagonal shape‐persistent macrocycles (SPMs) consisting of three pyridine and three phenol rings linked with acetylene bonds were developed as a preorganized host for saccharide recognition by push–pull‐type hydrogen bonding. Three tert‐butyl or 2,4,6‐triisopropylphenyl substituents were introduced on the host to suppress self‐aggregation by steric hindrance. In spite of the simple architecture, association constants Ka of the host with alkyl glycoside guests reached the order of 106 m ?1 on the basis of UV/Vis titration experiments. This glycoside recognition was much stronger than that in the cases of acyclic equivalent hosts because of the entropic advantage brought by preorganization of the hydrogen‐bonding sites. Solid–liquid extraction and liquid–liquid transport through a liquid membrane were demonstrated by using native saccharides, and much preference to mannose was observed. 相似文献
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Guest‐Induced Arylamide Polymer Helicity: Twist‐Sense Bias and Solvent‐Dependent Helicity Inversion 下载免费PDF全文
Peng Zhang Liang Zhang Ze‐Kun Wang Yun‐Chang Zhang Rong Guo Dr. Hui Wang Prof. Dr. Dan‐Wei Zhang Prof. Dr. Zhan‐Ting Li 《化学:亚洲杂志》2016,11(11):1725-1730
A benzene/naphthalene alternately incorporated amide polymer was synthesized and characterized. 1H NMR spectroscopy, fluorescence, and circular dichroism (CD) experiments indicated that, in chloroform, the polymer could be induced by the chiral l ‐aspartic acid dianion or one of its derivatives to form a helical tubular conformation with twist‐sense bias. CD titration studies showed that the l ‐aspartic acid dianion (8 equiv.) could lead to a maximum Cotton effect. It was also revealed that the twist‐sense bias obeyed the majority rule, and 70 % enantiomeric excess could realize the maximum helicity bias. Adding acetonitrile to the solution of chloroform caused inversion of the guest‐induced helicity bias of the polymer. 相似文献
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Salim Javed Dr. Mahipal Bodugam Dr. Jessica Torres Arghya Ganguly Prof. Paul R. Hanson 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(20):6755-6758
A series of one‐pot, sequential protocols was developed for the synthesis of novel macrocycles bearing α,β‐unsaturated chemotypes. The method highlights a phosphate tether‐mediated approach to establish asymmetry, and consecutive one‐pot, sequential processes to access the macrocycles with minimal purification procedures. This library amenable strategy provided diverse macrocycles containing α,β‐unsaturated carbon‐, sulfur‐, or phosphorus‐based warheads. 相似文献
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D3h‐Symmetric Porphyrin‐Based Rigid Macrocyclic Ligands for Multicofacial Multinuclear Complexes in a One‐Nanometer‐Sized Cavity 下载免费PDF全文
Yohei Ohkoda Akane Asaishi Tomoya Namiki Tomoaki Hashimoto Midori Yamada Koichiro Shirai Yuta Katagami Dr. Tomoaki Sugaya Prof. Makoto Tadokoro Prof. Akiharu Satake 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(33):11745-11756
The one‐step synthesis of D3h‐symmetric cyclic porphyrin trimers 1 composed of three 2,2′‐[4,4′‐bis(methoxycarbonyl)]bipyridyl moieties and three porphyrinatozinc moieties was achieved from a nickel‐mediated reductive coupling of meso‐5,15‐bis(6‐chloro‐4‐methoxycarbonylpyrid‐2‐yl)porphyrinatozinc. Although cyclic trimers 1 were obtained as a mixture that included other cyclic and acyclic porphyrin oligomers, an extremely specific separation was observed only for cyclic trimers 1 when using columns of silica gel modified with pyrenylethyl, cyanopropyl, and other groups. Structural analysis of cyclic trimers 1 was carried out by means of NMR spectroscopy and X‐ray crystallography. Treatment of an η3‐allylpalladium complex with a cyclic trimer gave a tris(palladium) complex containing three η3‐allylpalladium groups inside the space, which indicated that the bipyridyl moieties inside the ring could work as bidentate metalloligands. 相似文献
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Wojciech Pisula Dr. Marcel Kastler Dr. Changduk Yang Dr. Volker Enkelmann Dr. Klaus Müllen Prof. Dr. 《化学:亚洲杂志》2007,2(1):51-56
Two novel discotic macrocycles, substituted cyclohexa‐m‐phenylene (CHP) and cyclo‐3,6‐trisphenanthrylene (CTP), and the linear oligomer 3,3′:6′,3′′‐terphenanthrene (TP) as a model substance have been synthesized by repetitive cross‐coupling reactions. To correlate the molecular design with the supramolecular architecture and the established macroscopic order, 2D wide‐angle X‐ray scattering experiments were performed on mechanically extruded filaments. At room temperature in their crystalline phases, all three compounds revealed columnar assemblies in which the macrocycles self‐organized by π‐stacking interactions. The degree of macroscopic order was found to depend upon the planarity and stiffness of the aromatic core. The flexible CHP ring showed a poor macroscopic order of the columnar structures and a low isotropization temperature, whereas the more‐planar, less‐flexible CTP self‐assembled into well‐defined superstructures. The larger π‐stacking area and the more‐pronounced intermolecular interactions for CTP led to the formation of a mesophase over a very large temperature range. The surprising columnar organization of the “open” TP system was explained by back‐folding of the molecule into a ringlike structure. 相似文献
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Dr. Dmitry S. Turygin Dr. Michael Subat Prof. Vladimir V. Arslanov Prof. Burkhard König Prof. Maria A. Kalinina 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(34):10560-10568
The hydrogen‐bond‐guided self‐assembly of 5′‐ribonucleotides bearing adenine(A), cytosine (C), uracil (U), or guanine (G) bases from aqueous solution on a lipid‐like surface decorated with synthetic bis(ZnII–cyclen) (cyclen=1,4,7,10‐tetraazacyclodododecane) metal–complex receptor sites is described. The process was studied by using surface plasmon resonance spectroscopy. The data show that the mechanism of nucleotide binding to the 2D template is influenced by the chemistry of the bases and the pH value of the solution. In a neutral solution of pH 7.5, the process is cooperative and selective with respect to Watson–Crick pairs (A–U and C–G), which form stable double planes in accordance with the Chargaff rule. In a more acidic solution at pH 6.0, the interactions between complementary partners become non‐cooperative and the surface also stabilizes mismatched and wobble pairs due to the pH‐induced changes in the receptor coordination state. The results suggest that hydrogen bonding plays a key role in the self‐assembly of complementary nucleotides at the lipid‐like interface, and the cooperative character of the process stems from the ideal matching of the orientation and chemistry of all the interacting components with respect to each other in neutral solution. 相似文献
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Fine Tuning of β‐Peptide Foldamers: a Single Atom Replacement Holds Back the Switch from an 8‐Helix to a 12‐Helix 下载免费PDF全文
Dr. Amandine Altmayer‐Henzien Dr. Valérie Declerck Dr. Jonathan Farjon Prof. Dr. Denis Merlet Dr. Régis Guillot Prof. Dr. David J. Aitken 《Angewandte Chemie (International ed. in English)》2015,54(37):10807-10810
Cyclic homologated amino acids are important building blocks for the construction of helical foldamers. N‐aminoazetidine‐2‐carboxylic acid (AAzC), an aza analogue of trans‐2‐aminocyclobutanecarboxylic acid (tACBC), displays a strong hydrazino turn conformational feature, which is proposed to act as an 8‐helix primer. tACBC oligomers bearing a single N‐terminal AAzC residue were studied to evaluate the ability of AAzC to induce and support an 8‐helix along the oligopeptide length. While tACBC homooligomers assume a dominant 12‐helix conformation, the aza‐primed oligomers preferentially adopt a stabilized 8‐helix conformation for an oligomer length up to 6 residues. The (formal) single‐atom exchange at the N terminus of a tACBC oligomer thus contributes to the sustainability of the 8‐helix, which resists the switch to a 12‐helix. This effect illustrates atomic‐level programmable design for fine tuning of peptide foldamer architectures. 相似文献
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Jorge P. López‐Alonso Dr. Miguel A. Pardo‐Cea Irene Gómez‐Pinto Dr. Irene Fernández Dr. Avijit Chakrabartty Prof. Enrique Pedroso Prof. Carlos González Prof. Douglas V. Laurents Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(18):5314-5323
KIA7, a peptide with a highly restricted set of amino acids (Lys, Ile, Ala, Gly and Tyr), adopts a specifically folded structure. Some amino acids, including Lys, Ile, Ala, Gly and His, form under the same putative prebiotic conditions, whereas different conditions are needed for producing Tyr, Phe and Trp. Herein, we report the 3D structure and conformational stability of the peptide KIA7H, which is composed of only Lys, Ile, Ala, Gly and His. When the imidazole group is neutral, this 20‐mer peptide adopts a four‐helix bundle with a specifically packed hydrophobic core. Therefore, one‐pot prebiotic proteins with well‐defined structures might have arisen early in chemical evolution. The Trp variant, KIA7W, was also studied. It adopts a 3D structure similar to that of KIA7H and its previously studied Tyr and Phe variants, but is remarkably more stable. When tested for ribonucleolytic activity, KIA7H, KIA7W and even short, unstructured peptides rich in His and Lys, in combination with Mg++, Mn++ or Ni++ (but not Cu++, Zn++ or EDTA) specifically cleave the single‐stranded region in an RNA stem–loop. This suggests that prebiotic peptide–divalent cation complexes with ribonucleolytic activity might have co‐inhabited the RNA world. 相似文献