- Hydrophobic Vitamin B12. Part 6. Carbon-skeleton Rearrangement via Formation of Host-Guest Complexes derived from an 'Octopus Azaparacyclophane and hydrophobic Vitamin B12 Derivatives: a Novel Holoenzyme Model System
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The alkylation reactions of a hydrophobic vitamin B12 derivative with alkyl bromides in an 'octopus' azaparacyclophane having eight hydrocarbon chains have been investigated.Molecular discrimination has been shown to originate from electrostatic interaction between the octopus cyclophane and the alkyl bromides.Alkylation was enhanced by desolvation and proximity effects operating on the reacting species via formation of a ternary complex composed of the octopus cyclophane, the hydrophobic vitamin B12 derivative, and an alkyl halide.Carbon-skeleton rearrangement reactions of alkyl ligands bound to the hydrophobic vitamin B12 were found to be markedly favoured in the hydrophobic cavity provided by the octopus cyclophane, relative to the reactions in methanol and benzene, under anaerobic photolysis conditions at ordinary temperatures.The same reactions took place readily in solid benzene below 4 deg C under similar conditions.The central cobalt atom of the hydrophobic vitamin B12 participates in the rearrangement reaction via formation of a tight pair with an alkyl radical species.Non-enzymic rearrangement reactions have been shown here to proceed quite efficiently by employing a relevant apoenzyme model.
- Murakami, Yukito,Hisaeda, Yoshio,Kikuchi, Jun-ichi,Ohno, Teruhisa,Suzuki, Masashi,et al.
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- Intramolecular Halogen Transfer via Halonium Ion Intermediates in the Gas Phase
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The fragmentation of halogen-substituted protonated amines and quaternary ammonium ions (R1R2R3N+CH2(CH2)nX, where X = F, Cl, Br, I, n = 1, 2, 3, 4) was studied by electrospray ionization tandem mass spectrometry. A characteristic fragment ion (R1R2R3N+X) resulting from halogen transfer was observed in collision-induced dissociation. A new mechanism for the intramolecular halogen transfer was proposed that involves a reactive intermediate, [amine/halonium ion]. A potential energy surface scan using DFT calculation for CH2-N bond cleavage process of protonated 2-bromo-N,N-dimethylethanamine supports the formation of this intermediate. The bromonium ion intermediate-involved halogen transfer mechanism is supported by an examination of the ion/molecule reaction between isolated ethylenebromonium ion and triethylamine, which generates the N-bromo-N,N,N-triethylammonium cation. For other halogens, Cl and I also can be involved in similar intramolecular halogen transfer, but F cannot be involved. With the elongation of the carbon chain between the halogen (bromine as a representative example) and amine, the migration ability of halogen decreases. When the carbon chain contains two or three CH2 units (n = 1, 2), formal bromine cation transfer can take place, and the transfer is easier when n = 1. When the carbon chain contains four or five CH2 units (n = 3, 4), formal bromine cation transfer does not occur, probably because the five- and six-membered cyclic bromonium ions are very stable and do not donate the bromine to the amine.
- Chai, Yunfeng,Xiong, Xingchuang,Yue, Lei,Jiang, You,Pan, Yuanjiang,Fang, Xiang
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- Ion channel topography of the neuronal nicotinic acetylcholine receptor: Pharmacochemical approaches
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Forty-three bisammonium ganglionic blockers were synthesized to study the structure of the ion channel of nicotinic acetylcholine receptor. The conformational parameters of these blockers were studied, and their effects toward the ganglionic transmission in situ on the sympathetic feline superior cervical ganglia and in vitro on the parasympathetic guinea-pig small intestine ganglia were determined. A model of the binding site for the bisammonium ganglionic blockers in the neuronal ion channel was proposed.
- Gmiro,Brovtsyna,Serdyuk,Lukomskaya
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- Photoinduced and Redox-Induced Transmembrane Processes with Vesicle-Stabilized Colloidal Cadmium Sulfide and Multicharged Viologen Derivatives
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Colloidal cadmium sulfide (CdS) and methylviologen (MV2+) or new viologen derivatives carrying more positive charges were placed at specific sites of dihexadecyl phosphate (DHP) vesicles.Benzyl alcohol was used as a sacrificial electron donor to promote reduction of the viologens by photoexcited CdS colloid majority carriers.Transmission electron microscopy, 13C nuclear magnetic resonance, and differential scanning calorimetry were used for physical characterization.Photochemical events were followed by in situ optical and electrochemical monitoring.Redox-induced transmembrane diffusion, which had been found with MV2+, could be reduced by a factor 18 by using a triply charged viologen derivative and by a further factor of 30 in a configuration involving transmembrane electron transfer.In that case the quantum yield was ca. 0.05 at 410 nm, while virtually no reduced viologen leaking could be observed during at least 10 min.Physical evidence was found for a partial penetration of the CdS colloids into the DHP membrane.
- Tricot, Yves-M.,Porat, Ze'ev,Manassen, Joost
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- Thiol- And Disulfide-Containing Vancomycin Derivatives against Bacterial Resistance and Biofilm Formation
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Antibiotic-resistant and biofilm-associated infections constitute a rapidly growing issue. Use of the last-resort antibiotic vancomycin is under threat due to the increasing appearance of vancomycin-resistant bacteria as well as the formation of biofilms. Herein, we report a series of novel vancomycin derivatives carrying thiol- and disulfide-containing moieties. The new compounds exhibited enhanced antibacterial activity against a broad range of bacterial strains, including vancomycin-resistant microbes and Gram-negative bacteria. Moreover, all obtained derivatives demonstrated improved antibiofilm formation activity against VanB-resistant Enterococcus compared to vancomycin. This work establishes a promising strategy for combating drug-resistant bacterial infections or disrupting biofilm formation and advances the knowledge on the structural optimization of antibiotics with sulfur-containing modifications.
- Gademann, Karl,Shchelik, Inga S.
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supporting information
p. 1898 - 1904
(2021/11/16)
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- Compositions containing ionic liquids and their uses, in particular in organic synthesis
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An ionic liquid is used as liquid matrix for organic synthesis in homogeneous phase on soluble support, the ionic liquid being presented in liquid or solid form at ambient temperature, of formula A1+X1?, A1+ representing a cation, functional or non-functional, or a mixture of cations in which either none of the cations is functional or at least one of the cations is functional, and X1? an anion, functional or non-functional, or a mixture of anions in which either none of the anions is functional or at least one of the anions is functional.
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(2016/10/17)
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- Organic synthesis in soft wall-free microreactors: Real-time monitoring of fluorogenic reactions
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A new approach of "laboratory on a chip" (LOC) devoted to organic synthesis based on electrically operated ionic liquid microdroplets used as air-stable "soft" microreactors was recently introduced. A number of challenging issues have yet to be addressed
- Marchand,Dubois,Delattre,Vinet,Blanchard-Desce,Vaultier
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p. 6051 - 6055
(2008/12/22)
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- Ionic liquid droplet as e-microreactor
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A powerful approach combining a droplet-based, open digital microfluidic lab-on-a-chip using task-specific ionic liquids as soluble supports to perform solution-phase synthesis is reported as a new tool for chemical applications. The negligible volatility of ionic liquids enables their use as stable droplet reactors on a chip surface under air. The concept was validated with different ionic liquids and with a multicomponent reaction. Indeed, we showed that different ionic liquids can be moved by electrowetting on dielectric (EWOD), and their displacement was compared with aqueous solutions. Furthermore, we showed that mixing ionic liquids droplets, each containing a different reagent, in "open" systems is an efficient way of carrying supported organic synthesis. This was applied to Grieco's tetrahydroquinolines synthesis with different reagents. Analysis of the final product was performed off-line and on-line, and the results were compared with those obtained in a conventional reaction flask. This technology opens the way to easy synthesis of minute amounts of compounds ad libitum without the use of complex, expensive, and bulky robots and allows complete automation of the process for embedded chemistry in a portable device. It offers several advantages, including simplicity of use, flexibility, and scalability, and appears to be complementary to conventional microfluidic lab-on-a-chip devices usually based on continuous-flow in microchannels.
- Dubois, Philippe,Marchand, Gilles,Fouillet, Yves,Berthier, Jean,Douki, Thierry,Hassine, Fatima,Gmouh, Said,Vaultier, Michel
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p. 4909 - 4917
(2008/02/12)
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- Facile synthesis of (ω-bromoalkyl)trimethylammonium bromides
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Reaction of a 1,ω-dibromoalkane with trimethylamine in THF at room temperature precipitates the corresponding (ω-bromoalkyl)trimethylammonium bromide to cleanly form the mono-substituted product in the absence of the bis-quat salt.
- Bartsch, Richard A.,Zhao, Wenyi,Zhang, Zhi-Yi
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p. 2393 - 2398
(2007/10/03)
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