- Boronic acid fluorophore/β-cyclodextrin complex sensors for selective sugar recognition in water
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A novel boronic acid fluorophore 1/β-cyclodextrin (β-CyD) complex sensor for sugar recognition in water has been designed. The probe 1 bearing pyrene moiety as a fluorescent signal transducer exhibits no fluorescence emission, due to its aggregation in water containing 2% DMSO; however, the addition of β-CyD to this solution largely changes UV-vis and fluorescence spectra of 1 by forming an inclusion complex with β-CyD, and an efficient fluorescence emission response of 1/β-CyD complex upon sugar binding is found to be obtained at pH 7.5. The pH-fluorescence profile of the 1/β-CyD complex reveals that the boronate ester formation with fructose induces the apparent pKa shift from 7.95 ± 0.03 in the absence of fructose to 6.06 ± 0.03 in the presence of 30 mM fructose, resulting in the fluorescence emission response under the neutral condition. The spectral properties of 1 in 95% methanol:5% water (v/v), as well as the fluorescence quenching study of 1-methylpyrene with 4-methoxycarbonylphenyl-boronic acid 2, demonstrate that the response mechanism is based on the photoinduced electron transfer (PET) from the pyrene donor to the acid form of phenylboronic acid acceptor in 1, and thus, the proton dissociation of phenylboronic acid induced by sugar binding inhibits the PET system while increasing the fluorescence intensity of the pyrene moiety. To evaluate the binding ability and selectivity of the 1/β-CyD complex for monosaccharides in water, the response equilibria have been derived. The 1:1 binding constants of the 1/β-CyD complex obtained from the equilibrium analysis are in the order: D-fructose (2515 ± 134 M-1) ? L-arabinose (269 ± 28 M-1) > D-galactose (197 ± 28 M-1) > D-glucose (79 ± 33 M-1), which is consistent with the binding selectivity of phenylboronic acid.
- Tong,Yamauchi,Hayashita,Zhang,Smith,Teramae
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- Beyond Basicity: Discovery of Nonbasic DENV-2 Protease Inhibitors with Potent Activity in Cell Culture
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The viral serine protease NS2B-NS3 is one of the promising targets for drug discovery against dengue virus and other flaviviruses. The molecular recognition preferences of the protease favor basic, positively charged moieties as substrates and inhibitors, which leads to pharmacokinetic liabilities and off-target interactions with host proteases such as thrombin. We here present the results of efforts that were aimed specifically at the discovery and development of noncharged, small-molecular inhibitors of the flaviviral proteases. A key factor in the discovery of these compounds was a cellular reporter gene assay for the dengue protease, the DENV2proHeLa system. Extensive structure-activity relationship explorations resulted in novel benzamide derivatives with submicromolar activities in viral replication assays (EC50 0.24 μM), selectivity against off-target proteases, and negligible cytotoxicity. This structural class has increased drug-likeness compared to most of the previously published active-site-directed flaviviral protease inhibitors and includes promising candidates for further preclinical development.
- Kühl, Nikos,Leuthold, Mila M.,Behnam, Mira A. M.,Klein, Christian D.
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p. 4567 - 4587
(2021/05/06)
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- Hydroxyl radical-mediated oxidative cleavage of CC bonds and further esterification reaction by heterogeneous semiconductor photocatalysis
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A hydroxyl radical-mediated aerobic cleavage of alkenes and further sequence esterification reaction for the preparation of carbonyl compounds have been developed by using tubular carbon nitride (TCN) as a general heterogeneous photocatalyst under an oxygen atmosphere with visible light irradiation. This protocol has an excellent substrate scope and gives the desired aldehydes, ketones and esters in moderate to high yields. Importantly, this metal-free procedure employed photogenerated hydroxyl radicals in situ as green oxidation active species, avoiding the present additional initiators. The reaction could be carried out under solar light irradiation and was applicable to large-scale reactions. Furthermore, the recyclable TCN catalyst could be used several times without a significant loss of activities.
- Hong, Mei,Jia, Rui,Miao, Hongyan,Ni, Bangqing,Niu, Tengfei,Wang, Hui
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p. 6591 - 6597
(2021/09/10)
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- Transition-Metal-Free Borylation of Aryl Bromide Using a Simple Diboron Source
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In this study, we developed a simple transition-metal-free borylation reaction of aryl bromides. Bis-boronic acid (BBA), was used, and the borylation reaction was performed using a simple procedure at a mild temperature. Under mild conditions, aryl bromides were converted to arylboronic acids directly without any deprotection steps and purified by conversion to trifluoroborate salts. The functional group tolerance was considerably high. The mechanism study suggested that this borylation reaction proceeds via a radical pathway.
- Han, Min Su,Lim, Taeho,Ryoo, Jeong Yup
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p. 10966 - 10972
(2020/09/23)
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- Synthesis of 3,5-Disubstituted Isoxazoles through a 1,3-Dipolar Cycloaddition Reaction between Alkynes and Nitrile Oxides Generated from O-Silylated Hydroxamic Acids
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In this paper, we report the regioselective synthesis of 3,5-disubstituted isoxazoles by 1,3-dipolar cycloaddition between alkynyl dipolarophiles and nitrile oxide dipoles generated in-situ from O-silylated hydroxamic acids in the presence of trifluoromethanesulfonic anhydride and NEt3. Thanks to the mild, metal-free and oxidant-free conditions that this strategy offers, the reaction was successfully applied to a wide variety of alkynyl dipolarophiles, demonstrating the tolerance of this approach to diverse functional groups. In particular, we have shown that the method was compatible with biological molecules such as peptides and peptide nucleic acids (PNA). This protocol constitutes another example of metal-free 1,3-dipolar cycloaddition leading to the regioselective formation of isoxazoles.
- Carloni, Laure-Elie,Mohnani, Stefan,Bonifazi, Davide
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supporting information
p. 7322 - 7334
(2019/11/05)
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- Bedford-type palladacycle-catalyzed miyaura borylation of aryl halides with tetrahydroxydiboron in water
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A mild aqueous protocol for palladium catalyzed Miyaura borylation of aryl iodides, aryl bromides and aryl chlorides with tetrahydroxydiboron (BBA) as a borylating agent is developed. The developed methodology requires low catalyst loading of Bedford-type palladacycle catalyst (0.05 mol %) and works best under mild reaction conditions at 40 °C in short time of 6 h in water. In addition, our studies show that for Miyaura borylation using BBA in aqueous condition, maintaining a neutral reaction pH is very important for reproducibility and higher yields of corresponding borylated products. Moreover, our protocol is applicable for a broad range of aryl halides, corresponding borylated products are obtained in excellent yields up to 93% with 29 examples demonstrating its broad utility and functional group tolerance.
- Zernickel, Anna,Du, Weiyuan,Ghorpade, Seema A.,Sawant, Dinesh N.,Makki, Arwa A.,Sekar, Nagaiyan,Eppinger, J?rg
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p. 1842 - 1851
(2018/02/23)
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- A 4 - carboxyl preparation process of boric acid (by machine translation)
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The invention discloses a 4 - carboxyl boric acid process. In order to to iodine benzoic acid as the raw material, by esterification reaction, sediment reaction and hydrolysis reaction to obtain the target product 4 - carboxyl boric acid, the total yield can reach 88.7%. The process route raw materials are cheap and easy to obtain, after-treatment is convenient, high yield, easy industrialized application. (by machine translation)
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- Remote-Controlled Release of Singlet Oxygen by the Plasmonic Heating of Endoperoxide-Modified Gold Nanorods: Towards a Paradigm Change in Photodynamic Therapy
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The photodynamic therapy of cancer is contingent upon the sustained generation of singlet oxygen in the tumor region. However, tumors of the most metastatic cancer types develop a region of severe hypoxia, which puts them beyond the reach of most therapeutic protocols. More troublesome, photodynamic action generates acute hypoxia as the process itself diminishes cellular oxygen reserves, which makes it a self-limiting method. Herein, we describe a new concept that could eventually lead to a change in the 100 year old paradigm of photodynamic therapy and potentially offer solutions to some of the lingering problems. When gold nanorods with tethered endoperoxides are irradiated at 808 nm, the endoperoxides undergo thermal cycloreversion, resulting in the generation of singlet oxygen. We demonstrate that the amount of singlet oxygen produced in this way is sufficient for triggering apoptosis in cell cultures. EPT sees the light: When gold nanorods with tethered endoperoxides are irradiated with near-infrared light, the endoperoxides undergo thermal cycloreversion, resulting in the generation of singlet oxygen. The amount of singlet oxygen generated by these nanocomposites is sufficient for triggering apoptosis in cell cultures.
- Kolemen, Safacan,Ozdemir, Tugba,Lee, Dayoung,Kim, Gyoung Mi,Karatas, Tugce,Yoon, Juyoung,Akkaya, Engin U.
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p. 3606 - 3610
(2016/03/23)
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- Reticular Chemistry at Its Best: Directed Assembly of Hexagonal Building Units into the Awaited Metal-Organic Framework with the Intricate Polybenzene Topology, pbz-MOF
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The ability to direct the assembly of hexagonal building units offers great prospective to construct the awaited and looked-for hypothetical polybenzene (pbz) or "cubic graphite" structure, described 70 years ago. Here, we demonstrate the successful use of reticular chemistry as an appropriate strategy for the design and deliberate construction of a zirconium-based metal-organic framework (MOF) with the intricate pbz underlying net topology. The judicious selection of the perquisite hexagonal building units, six connected organic and inorganic building blocks, allowed the formation of the pbz-MOF-1, the first example of a Zr(IV)-based MOF with pbz topology. Prominently, pbz-MOF-1 is highly porous, with associated pore size and pore volume of 13 ? and 0.99 cm3 g-1, respectively, and offers high gravimetric and volumetric methane storage capacities (0.23 g g-1 and 210.4 cm3 (STP) cm-3 at 80 bar). Notably, the pbz-MOF-1 pore system permits the attainment of one of the highest CH4 adsorbed phase density enhancements at high pressures (0.15 and 0.21 g cm-3 at 35 and 65 bar, respectively) as compared to benchmark microporous MOFs.
- Alezi, Dalal,Spanopoulos, Ioannis,Tsangarakis, Constantinos,Shkurenko, Aleksander,Adil, Karim,Belmabkhout, Youssef,O'Keeffe, Michael,Eddaoudi, Mohamed,Trikalitis, Pantelis N.
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supporting information
p. 12767 - 12770
(2016/10/13)
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- Spectroscopic and computational investigations of the thermodynamics of boronate ester and diazaborole self-assembly
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The solution phase self-assembly of boronate esters, diazaboroles, oxathiaboroles, and dithiaboroles from the condensation of arylboronic acids with aromatic diol, diamine, hydroxythiol, and dithiol compounds in chloroform has been investigated by 1H NMR spectroscopy and computational methods. Six arylboronic acids were included in the investigations with each boronic acid varying in the substituent at its 4-position. Both computational and experimental results show that the para-substituent of the arylboronic acid does not significantly influence the favorability of forming a condensation product with a given organic donor. The type of donor, however, greatly influences the favorability of self-assembly. 1H NMR spectroscopy indicates that condensation reactions between arylboronic acids and catechol to give boronate esters are the most favored thermodynamically, followed by diazaborole formation. Computational investigations support this conclusion. Neither oxathiaboroles nor dithiaboroles form spontaneously at equilibrium in chloroform at room temperature. Computational results suggest that the effect of borylation on the frontier orbitals of each donor helps to explain differences in the favorability of their condensation reactions with arylboronic acids. The results can inform the use of boronic acids as they are increasingly utilized in the dynamic self-assembly of organic materials and as components in dynamic combinatorial libraries.
- Goldberg, Alexander R.,Northrop, Brian H.
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p. 969 - 980
(2016/02/18)
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- Nickel-catalyzed borylation of halides and pseudohalides with tetrahydroxydiboron [B2(OH)4]
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Arylboronic acids are gaining increased importance as reagents and target structures in a variety of useful applications. Recently, the palladium-catalyzed synthesis of arylboronic acids employing the atom-economical tetrahydroxydiboron (BBA) reagent has been reported. The high cost associated with palladium, combined with several limitations of both palladium- and copper-catalyzed processes, prompted us to develop an alternative method. Thus, the nickel-catalyzed borylation of aryl and heteroaryl halides and pseudohalides using tetrahydroxydiboron (BBA) has been formulated. The reaction proved to be widely functional group tolerant and applicable to a number of heterocyclic systems. To the best of our knowledge, the examples presented here represent the only effective Ni-catalyzed Miyaura borylations conducted at room temperature.
- Molander, Gary A.,Cavalcanti, Livia N.,Garcia-Garcia, Carolina
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p. 6427 - 6439
(2013/07/26)
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- A "strongly" self-catenated metal-organic framework with the highest topological density among 3,4-coordinated nets
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A new type of 3D "strongly" self-catenated metal-organic framework (SDU-9) has been constructed from [Cu2(COO)4] paddlewheel secondary building units and a tripodal carboxylate linker. SDU-9 ([Cu6(H2O)6L4]·24H 2O, where [H3L = 4,4′,4″-(hydroxysilanetriyl) tris(triphenyl-4-carboxylic acid), represents a rare example of a highly symmetrical coordination network and extremely tight self-catenation. To the best of our knowledge, SDU-9 has the highest topological density among all known 3,4-coordinated nets.
- Ma, Huiqing,Sun, Di,Zhang, Liangliang,Wang, Rongming,Blatov, Vladislav A.,Guo, Jie,Sun, Daofeng
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supporting information
p. 10732 - 10734
(2013/10/22)
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- Scope of the palladium-catalyzed aryl borylation utilizing bis-boronic acid
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The Suzuki-Miyaura reaction has become one of the more useful tools for synthetic organic chemists. Until recently, there did not exist a direct way to make the most important component in the coupling reaction, namely the boronic acid. Current methods to make boronic acids often employ harsh or wasteful reagents to prepare boronic acid derivatives and require additional steps to afford the desired boronic acid. The scope of the previously reported palladium-catalyzed, direct boronic acid synthesis is unveiled, which includes a wide array of synthetically useful aryl electrophiles. It makes use of the newly available second generation Buchwald XPhos preformed palladium catalyst and bis-boronic acid. For ease of isolation and to preserve the often sensitive C-B bond, all boronic acids were readily converted to their more stable trifluoroborate counterparts.
- Molander, Gary A.,Trice, Sarah L. J.,Kennedy, Steven M.,Dreher, Spencer D.,Tudge, Matthew T.
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supporting information; experimental part
p. 11667 - 11673
(2012/09/05)
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- Metal-free chlorodeboronation of organotrifluoroborates
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A mild and metal-free method for the chlorodeboronation of organotrifluoroborates using trichloroisocyanuric acid (TCICA) was developed. Aryl-, heteroaryl-, alkenyl-, alkynyl-, and alkyltrifluoroborates were converted into the corresponding chlorinated products in good yields. This method proved to be tolerant of a broad range of functional groups.
- Molander, Gary A.,Cavalcanti, Livia N.
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experimental part
p. 7195 - 7203
(2011/10/13)
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- Predicting the structure of supramolecular dendrimers via the analysis of libraries of AB3 and constitutional isomeric AB2 biphenylpropyl ether self-assembling dendrons
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The synthesis of 4′-hydroxy-4-biphenylpropionic, 3′,4′- dihydroxy-4-biphenylpropionic, 3′,5′-dihydroxy-4-biphenylpropionic, and 3′,4′,5′-trihydroxy-4-biphenylpropionic methyl esters via three efficient and modular strategies including one based on Ni-catalyzed borylation and sequential cross-coupling is reported. These building blocks were employed in a convergent iterative approach to the synthesis of one library of 3,4,5-trisubstituted and two libraries of constitutional isomeric 3,4- and 3,5-disubstituted biphenylpropyl ether dendrons. Structural and retrostructural analysis of supramolecular dendrimers revealed that biphenylpropyl ether dendrons self-assemble and self-organize into the same periodic lattices and quasi-periodic arrays observed in previously reported libraries, but with larger dimensions, different mechanisms of self-assembly, and improved solubility, thermal, acidic, and oxidative stability. The different mechanisms of self-assembly led to the discovery of two new supramolecular structures. The first represents a new banana-like lamellar crystal with a four layer repeat. The second is a giant vesicular sphere self-assembled from 770 dendrons that exhibits an ultrahigh molar mass of 1.73 × 106 g/mol. Thus, the enhanced size of the self-assembled structures constructed from biphenylpropyl ether dendrons permitted for the first time discrimination of various molecular mechanisms of spherical self-assembly and elaborated a continuum between small filled spheres and very large hollow spheres that is dictated by the primary structure of the dendron. The comparative analysis of libraries of biphenylpropyl ether dendrons with the previously reported libraries of benzyl-, phenylpropyl-, and biphenyl-4-methyl ether dendrons demonstrated biomimetic self-assembly wherein the primary structure of the dendron and to a lesser extent the structure of its repeat unit determines the supramolecular tertiary structure. A "nanoperiodic table" of self-assembling dendrons and supramolecular dendrimers that allows the prediction of the general features of tertiary structures from primary structures was elaborated.
- Rosen, Brad M.,Wilson, Daniela A.,Wilson, Christopher J.,Peterca, Mihai,Won, Betty C.,Huang, Chenghong,Lipski, Linda R.,Zeng, Xiangbing,Ungar, Goran,Heiney, Paul A.,Percec, Virgil
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p. 17500 - 17521
(2010/03/25)
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- Novel 4-Aminopiperidine Derivatives
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Novel substituted 4-aminopiperidine derivatives of the formula I: wherein n, R1, Y, and are as defined in claim 1, and optically pure enantiomers, mixtures of enantiomers, racemates, diastereomers, mixtures of diastereomers, diastereomeric racemates, mixtures of diastereomeric racemates and meso-forms, as well as salts and solvent complexes of such compounds, and morphological forms, that exhibit useful parasite aspartic proteases inhibiting properties and can thus be used in the form of pharmaceutical compositions as antimalarial medicines.
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Page/Page column 44-45
(2010/11/30)
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- Expanding the structural diversity of self-assembling dendrons and supramolecular dendrimers via complex building blocks
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The design and synthesis of the first examples of AB4 and AB5 dendritic building blocks with complex architecture are reported. Structural and retrostructural analysis of supramolecular dendrimers self-assembled from hybrid dendrons based on different combinations of AB 4 and AB5 building blocks with AB2 and AB 3 benzyl ether dendrons demonstrated that none of these new hybrid dendrons exhibit the previously encountered conformations of libraries of benzyl ether dendrons. These hybrid dendrons enabled the discovery of some highly unusual tapered and conical dendrons generated by the intramolecular backfolding of their repeat units and of their apex. The new back-folded tapered dendrons have double thickness and self-assemble into pine-tree-like columns exhibiting a long-range 7/2 helical order. The back-folded conical dendrons self-assemble into spherical dendrimers. Non-back-folded truncated conical dendrons were also discovered. They self-assemble into spherical dendrimers with a less densely packed center. The discovery of dendrons displaying a novel crown-like conformation is also reported. Crown-like dendrons self-assemble into long-range 5/1 helical pyramidal columns. The long-range 7/2 and 5/1 helical structures were established by applying, for the first time, the helical diffraction theory to the analysis of X-ray patterns obtained from oriented fibers of supramolecular dendrimers.
- Percec, Virgil,Won, Betty C.,Peterca, Mihai,Heiney, Paul A.
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p. 11265 - 11278
(2008/03/14)
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- Noncryogenic I/Br-Mg exchange of aromatic halides bearing sensitive functional groups using i-PrMgCl-Bis[2-(N,N-dimethylamino)ethyl] ether complexes
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Iodo- and bromoaromatics bearing sensitive carboxylic ester and cyano groups underwent a selective halide-magnesium exchange with isopropylmagnesium chloride at ambient temperature in the presence of bis[2-(N,N-dimethylamino) ethyl] ether to afford the corresponding Grignard reagents. The newly formed reactive Grignard reagents were allowed to react with electrophiles such as trimethylborate to afford arylboronic acids in good to excellent yields.
- Wang, Xiao-Jun,Sun, Xiufeng,Zhang, Li,Xu, Yibo,Krishnamurthy, Dhileepkumar,Senanayake, Chris H.
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p. 305 - 307
(2007/10/03)
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- Formation of boroxine: Its stability and thermodynamic parameters in solution
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Condensation of three boronic acids proceeding at room temperature gave their corresponding boroxines; NMR spectral measurements revealed that the reaction was reversible at room temperature, that electron-donating groups supported the formation of boroxine, and that entropically driven forces promoted the formation of boroxine in solution.
- Tokunaga, Yuji,Ueno, Hiroki,Shimomura, Youji,Seo, Toshihiro
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p. 787 - 790
(2007/10/03)
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- Quaternary ammonium salts and their use
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This invention is to provide a compound for antagonizing CCR5, said compound being represented by the formula: wherein R1 is an optionally substituted phenyl or an optionally substituted thienyl; Y is -CH2-, -S- or -O-; and R2, R3 and R4 are independently an optionally substituted aliphatic hydrocarbon group or an optionally substituted alicyclic heterocyclic ring group, and being effective for the prevention and treatment of infectious disease of HIV.
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- Heterocyclic compounds
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The invention concerns pharmaceutically useful compounds of the formula I, in which A1, A2, A3, A4, B1, m, Ar, W, X, Y, Z and R1 have any of the meanings defined herein, and their pharmaceutically acceptable salts, and pharmaceutical compositions containing them. The novel compounds possess endothelin receptor antagonist activity and are useful, for example, in the treatment of diseases or medical conditions in which elevated or abnormal levels of endothelin play a significant causative role. The invention further concerns processes for the manufacture of the novel compounds and the use of the compounds in medical treatment.
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- Selective monosaccharide transport through lipid bilayers using boronic acid carriers
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Twenty-one boronic acids were studied for their ability to transport saccharides in and out of liposomes. The rates of liposome efflux were determined using an enzymatic assay, whereas the influx studies used a radiotracer method. All boronic acids examined, except those that were highly hydrophilic, facilitated monosaccharide transport. The order of transport selectivity was sorbitol > fructose > glucose. The disaccharides maltose and sucrose were not transported to any significant degree. Facilitated transport was demonstrated with a variety of liposome types, including multilamellar and unilamellar vesicles with anionic or cationic polar lipid additives. Transport mechanism studies included the accumulation of structure-activity data, as well as systematic investigations of various environmental changes such as pH, added salt, membrane potential, and temperature. Overall, the evidence is strongly in favor of a membrane carrier mechanism. The boronic acid combines reversibly with a diol group on the monosaccharide to produce a tetrahedral, anionic boronate, which is the major complexed structure in bulk, aqueous solution. At the bilayer surface, the tetrahedral boronate is in equilibrium with its neutral, trigonal form, which is the actual transported species. At low carrier concentrations, a first-order dependence on carrier was observed indicating that the transported species was a 1:1 sugar-boronate. At higher carrier concentrations the kinetic order approached 2, suggesting the increased participation of a 1:2 sugar-bisboronate transport pathway. The effect of boronic acids on liposomal bilayer fluidity was probed by fluorescence spectroscopy using appropriate reporter molecules. Adding cholesterol to the liposome membranes reduced translational fluidity by 'packing and ordering' the bilayer. Addition of lipophilic arylboronic acids (either free or complexed with monosaccharides) induced a similar but smaller effect.
- Westmark, Pamela R.,Gardiner, Stephen J.,Smith, Bradley D.
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p. 11093 - 11100
(2007/10/03)
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- Synthesis and iodination of methyl 4-tri-n-butylstannylbenzoate, p-(methoxycarbonyl)phenylmercuric chloride and p-(methoxycarbonyl)phenylboronic acid
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Synthesis of methyl 4-tri-n-butylstannylbenzoate (1) was accomplished by reaction of methyl 4-bromobenzoate with hexabutylditin and palladium catalyst.Transmetallation of 1 with mercuric acetate yielded the corresponding arylmercuric acetate 4 which was r
- Hylarides, Mark D.,Wilbur, D. Scott,adley, Stephen W.,Fritzberg, Alan R.
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p. 259 - 266
(2007/10/02)
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