共查询到20条相似文献,搜索用时 31 毫秒
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Dr. Julián Valero Dr. Beatriu Escuder Dr. Juan F. Miravet Prof. Javier de Mendoza 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(41):13038-13047
The chiral bicyclic diguanidinium chloride 1 forms gels in aromatic apolar solvents. The gels were characterized at different levels of organization, from the macroscopic to the molecular level by using microscopy, spectroscopy, and powder X‐ray diffraction. The dependency on chirality has been highlighted by circular dichroism and electron microscopy. Furthermore, the gel has been shown to be effectively responsive to anionic stimuli, thus allowing the reversible control of the organic‐phase gelation in contact with different salted aqueous solutions. 相似文献
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Qingxian Jin Dr. Li Zhang Xuefeng Zhu Dr. Pengfei Duan Prof. Dr. Minghua Liu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(16):4916-4922
New amphiphilic gelators that contained both Schiff base and L ‐glutamide moieties, abbreviated as o‐SLG and p‐SLG, were synthesized and their self‐assembly in various organic solvents in the absence and presence of metal ions was investigated. Gelation test revealed that o‐SLG formed a thermotropic gel in many organic solvents, whilst p‐SLG did not. When metal ions, such as Cu2+, Zn2+, Mg2+, Ni2+, were added, different behaviors were observed. The addition of Cu2+ induced p‐SLG to from an organogel. In the case of o‐SLG, the addition of Cu2+ and Mg2+ ions maintained the gelating ability of the compound, whilst Zn2+ and Ni2+ ions destroyed the gel. In addition, the introduction of Cu2+ ions caused the nanofiber gel to perform a chiral twist, whilst the Mg2+ ions enhanced the fluorescence of the gel. More interestingly, the Mg2+‐ion‐mediated organogel showed differences in the fluorescence quenching by D ‐ and L ‐tartaric acid, thus showing a chiral recognition ability. 相似文献
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《化学:亚洲杂志》2017,12(8):841-845
Sequence‐defined chiral polyimides comprising identical asymmetric diamine monomers arranged in different directions along the main chain were designed and prepared. These new sequence‐defined polymers exhibit sequence‐dependent self‐assembly behaviors and responses to ibuprofen enantiomers, as revealed by their chiroptical spectra and gelation properties. For the first time, the self‐assembly of polymers and their interactions with guest molecules have been successfully controlled by means of the directional arrangement of the monomers in their polymer backbones. 相似文献
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Prof. Francesco Sannicolò Prof. Patrizia R. Mussini Prof. Tiziana Benincori Prof. Rocco Martinazzo Dr. Serena Arnaboldi Giulio Appoloni Dr. Monica Panigati Dr. Elsa Quartapelle Procopio Valentina Marino Dr. Roberto Cirilli Dr. Simone Casolo Prof. Wlodzimierz Kutner Dr. Krzysztof Noworyta Dr. Agnieszka Pietrzyk‐Le Zofia Iskierko Katarzyna Bartold 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(31):10839-10847
The racemate of an inherently chiral “spider‐like” octathiophene monomer T83 , in which chirality is generated by torsion in its backbone, was synthesized. The racemate was resolved into configurationally stable antipodes by HPLC on a chiral stationary phase. Electrooxidation of the enantiomers resulted in materials displaying high enantiorecognition ability towards the antipodes of some chiral probes. Moreover, the T83 racemate demonstrated great aptitude to stimulate formation of 3D rigid architectures if used as a cross‐linking monomer for molecular imprinting. This feature was exploited to devise a molecularly imprinted polymer‐based chemosensor selective for a thymine–adenine oligonucleotide. 相似文献
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Yan Meng Xing Dai Minsi Xin Dr. Chuanjin Tian Hang Liu Prof. Mingxing Jin Prof. Zhigang Wang Prof. Rui‐Qin Zhang 《Chemphyschem》2014,15(13):2672-2675
We computationally study the transition process of a chiral difluorobenzo[c]phenanthrene (DFBcPh) molecule within non‐polar fullerene C260 to explore the confinement effect. We find blue‐shifts in the infrared and Raman spectra of the molecule inside the fullerene relative to those of isolated systems. Six types of spectrum features of the molecule appear in the 0–60 cm?1 band. Interestingly, the energy barrier of the chiral transformation of the molecule is elevated by 15.88 kcal mol?1 upon the confinement by the fullerene, indicating improvement in the stability of the enantiomers. The protection by C260 lowers the highest occupied molecular orbital energy level and lifts the lowest unoccupied molecular orbital energy level of the chiral molecule such that the chiral molecule is further chemically stabilized. We concluded that the confinement environment has an impact at the nanoscale on the enantiomer transformation process of the chiral molecule. 相似文献
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Alison J. Fugard Antti S. K. Lahdenper Jaqueline S. J. Tan Aroonroj Mekareeya Robert S. Paton Martin D. Smith 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(9):2821-2824
Non‐biaryl atropisomers are valuable in medicine, materials, and catalysis, but their enantioselective synthesis remains a challenge. Herein, a counterion‐mediated O‐alkylation method for the generation of atropisomeric amides with an er up to 99:1 is outlined. This dynamic kinetic resolution is enabled by the observation that the rate of racemization of atropisomeric naphthamides is significantly increased by the presence of an intramolecular O?H???NCO hydrogen bond. Upon O‐alkylation of the H‐bond donor, the barrier to rotation is significantly increased. Quantum calculations demonstrate that the intramolecular H‐bond reduces the rotational barrier about the aryl–amide bond, stabilizing the planar transition state for racemization by approximately 40 kJ mol?1, thereby facilitating the observed dynamic kinetic resolution. 相似文献
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An efficient four‐step synthetic strategy for cis‐2,5‐disubstituted chiral piperazines derived from amino‐acid‐based aziridines is described. The key steps in this strategy are the highly regioselective boron trifluoride diethyl etherate (BF3 ⋅ OEt2)‐mediated ring‐opening of less‐reactive N‐Ts chiral aziridines by α‐amino acid methyl ester hydrochloride followed by Mitsunobu cyclization. This protocol has been used in an attempt to construct the piperazine core framework of natural product (+)‐piperazinomycin. 相似文献
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Dr. Paul Benndorf Dipl.‐Chem. Jochen Kratsch Larissa Hartenstein Dipl.‐Chem. Corinna M. Preuss Prof. Dr. Peter W. Roesky 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(45):14454-14463
The treatment of the recently reported potassium salt (S)‐N,N′‐bis‐(1‐phenylethyl)benzamidinate ((S)‐KPEBA) and its racemic isomer (rac‐KPEBA) with anhydrous lanthanide trichlorides (Ln=Sm, Er, Yb, Lu) afforded mostly chiral complexes. The tris(amidinate) complex [{(S)‐PEBA}3Sm], bis(amidinate) complexes [{Ln(PEBA)2(μ‐Cl)}2] (Ln=Sm, Er, Yb, Lu), and mono(amidinate) compounds [Ln(PEBA)(Cl)2(thf)n] (Ln=Sm, Yb, Lu) were isolated and structurally characterized. As a result of steric effects, the homoleptic 3:1 complexes of the smaller lanthanide atoms Yb and Lu were not accessible. Furthermore, chiral bis(amidinate)–amido complexes [{(S)‐PEBA}2Ln{N(SiMe3)2}] (Ln=Y, Lu) were synthesized by an amine‐elimination reaction and salt metathesis. All of these chiral bis‐ and tris(amidinate) complexes had additional axial chirality and they all crystallized as diastereomerically pure compounds. By using rac‐PEBA as a ligand, an achiral meso arrangement of the ligands was observed. The catalytic activities and enantioselectivities of [{(S)‐PEBA}2Ln{N(SiMe3)2}] (Ln=Y, Lu) were investigated in hydroamination/cyclization reactions. A clear dependence of the rate of reaction and enantioselectivity on the ionic radius was observed, which showed higher reaction rates but poorer enantioselectivities for the yttrium compound. 相似文献
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Dr. Francisco Rodríguez‐Llansola Dr. Daniel Hermida‐Merino Belén Nieto‐Ortega Dr. Francisco J. Ramírez Prof. Juan T. López Navarrete Prof. Juan Casado Prof. Ian W. Hamley Dr. Beatriu Escuder Dr. Wayne Hayes Dr. Juan F. Miravet 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(46):14725-14731
A chiral bisurea‐based superhydrogelator that is capable of forming supramolecular hydrogels at concentrations as low as 0.2 mM is reported. This soft material has been characterized by thermal studies, rheology, X‐ray diffraction analysis, transmission electron microscopy (TEM), and by various spectroscopic techniques (electronic and vibrational circular dichroism and by FTIR and Raman spectroscopy). The expression of chirality on the molecular and supramolecular levels has been studied and a clear amplification of its chirality into the achiral analogue has been observed. Furthermore, thermal analysis showed that the hydrogelation of compound 1 has a high response to temperature, which corresponds to an enthalpy‐driven self‐assembly process. These particular thermal characteristics make these materials easy to handle for soft‐application technologies. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2018,130(33):10704-10708
MicroRNAs (miRNAs), a kind of single‐stranded small RNA molecules, play a crucial role in physiological and pathological processes in human beings. We describe here the detection of miRNA, by side‐by‐side self‐assembly of plasmonic nanorod dimers in living cells, which gives rise to a distinct intense chiroplasmonic response and surface‐enhanced Raman scattering (SERS). The dynamic assembly of chiral nanorods was confirmed by fluorescence resonance energy transfer (FRET), also in living cells. Our study provides insights into in situ self‐assembly of plasmonic probes for the real‐time measurement of biomarkers in living cells. This could improve the current understanding of cellular RNA–protein complexes, pharmaco‐genomics, and genetic diagnosis and therapies. 相似文献
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Dr. Kun Liu Xiangfei Wu Dr. S. B. Jennifer Kan Dr. Seiji Shirakawa Prof. Dr. Keiji Maruoka 《化学:亚洲杂志》2013,8(12):3214-3221
Catalytic asymmetric synthesis of axially chiral o‐iodoanilides and o‐tert‐butylanilides as useful chiral building blocks was achieved by means of binaphthyl‐modified chiral quaternary ammonium‐salt‐catalyzed N‐alkylations under phase‐transfer conditions. The synthetic utility of axially chiral products was demonstrated in various transformations. For example, axially chiral N‐allyl‐o‐iodoanilide was transformed to 3‐methylindoline by means of radical cyclization with high chirality transfer from axial chirality to C‐centered chirality. Furthermore, stereochemical information on axial chirality in o‐tert‐butylanilides could be used as a template to control the stereochemistry of subsequent transformations. The transition‐state structure of the present phase‐transfer reaction was discussed on the basis of the X‐ray crystal structure of ammonium anilide, which was prepared from binaphthyl‐modified chiral ammonium bromide and o‐iodoanilide. The chiral tetraalkylammonium bromide as a phase‐transfer catalyst recognized the steric difference between the ortho substituents on anilide to obtain high enantioselectivity. The size and structural effects of the ortho substituents on anilide were investigated, and a wide variety of axially chiral anilides that possess various functional groups could be synthesized with high enantioselectivities. This method is the only general way to access a variety of axially chiral anilides in a highly enantioselective fashion reported to date. 相似文献
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Guang‐Hui Ouyang Yan‐Mei He Yong Li Jun‐Feng Xiang Prof. Dr. Qing‐Hua Fan 《Angewandte Chemie (International ed. in English)》2015,54(14):4334-4337
An aza‐crown ether, modified phosphoramidite ligand, has been designed and synthesized. The ON/OFF reversible switch of catalytic activity for its rhodium catalyst was thoroughly investigated in the asymmetric hydrogenation of dehydroamino acid esters modulated by host–guest interactions. In the OFF state, the catalyst is almost inactive (less than 1 % conversion) because of the formation of an intermolecular sandwich complex by two aza‐crown ether moities and the cationic rhodium metal center. In using alkali‐metal‐cations as the trigger, the catalytic activity was turned ON and consequently resulted in full conversions and excellent enantioselectivities (up to 98 % ee). 相似文献
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Synthesis of Chiral Aminocyclopropanes by Rare‐Earth‐Metal‐Catalyzed Cyclopropene Hydroamination
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Dr. Huai‐Long Teng Dr. Yong Luo Dr. Baoli Wang Dr. Liang Zhang Dr. Masayoshi Nishiura Prof. Dr. Zhaomin Hou 《Angewandte Chemie (International ed. in English)》2016,55(49):15406-15410
The search for efficient and selective routes for the synthesis of chiral aminocyclopropane derivatives is of great interest and importance as these structures are important components of biologically active natural products and pharmaceuticals. We herein report the enantioselective intermolecular hydroamination of substituted cyclopropenes with various amines catalyzed by chiral half‐sandwich rare‐earth‐metal complexes. This method constitutes a 100 % atom‐efficient route for the synthesis of a variety of chiral α‐aminocyclopropane derivatives in high yields (up to 96 %) and excellent stereoselectivity (up to >20:1 d.r. and 99 % ee) under mild reaction conditions (25 °C). 相似文献