- Self-assembly of bis-β-diketone-based [M2 L 2] dinuclear platforms into 2-dimensional coordination polymers
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A bis-β-diketone ligand incorporating a 3,5-substituted pyridine ring between its two β-diketone domains (1,1′-(pyridine-3,5-diyl)bis(4,4-dimethylpentane-1,3-dione), H2L1) and its interaction with three divalent cations (Cu2+, Zn2+ and Pd2+) is reported. Charge neutral dinuclear metallocycles of type [M2L12] were obtained in each case and their X-ray structures determined. [Pd2L12] incorporates two square-planar O4-coordinated metal centres. The zinc(ii) and copper(ii) complexes contain five-coordinate O4N1-metal centres in which the pyridyl nitrogen from adjacent [M2L12] metallocycles coordinates apically forming two-dimensional coordination polymers of type {[Zn2L12]n(dmf)n} and {[Cu2L12]n(dmf)n}. Desolvation of the coordination polymers led to loss of crystallinity.
- Brock,McMurtrie, John C.,Clegg
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- Design, synthesis, and structural characterization of a new class of ferrocene-containing heterometallic triple-stranded helicates
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The new ditopic organoiron ligand, [3,5-bis(1-ferrocenyl-prop-3-enol-1-one) (pyridine)] (H2L3,5), has been prepared and the reactions of its dianion (Na2L3,5) with M3+ ions (M = Ga or In) yield a new class of "3d-np block" heterometallic triple-stranded helicates, M2(L3,5)3, by the self-assembly process. The X-ray structural analysis of the new ligand shows that it is in the enolic form with each enolic carbon bonded to the pyridine ring and each carbonyl carbon connected to a ferrocene moiety; overall, the nonferrocenyl part of the molecule is nearly planar. The M2(L 3,5)3 (M = Ga or In) complexes are helicates with three ligand strands, each of which is twisted into an S-shape, coordinating to two metal ions, each of which is in a distorted octahedral geometry. The new helicates are observed as a racemic mixture in the solid state by single-crystal X-ray analysis, and in solution by NMR, with both the left-handed Λ,Λ-and the right-handed Δ,Δ-isomers present. Variable-temperature 1H NMR study of the Ga2(L 3,5)3 helicate indicates that the right-handed Δ,Δ-isomer and left-handed Λ,Λ-isomer equilibrate through a heterochiral Λ,Δ-intermediate by a concerted twist motion of one-half of the dinuclear complex through a trigonal prismatic transition state, according to the Bailar twist mechanism. Electrochemical properties of the ligand (H2L3,5) and the M2(L 3,5)3 helicates were investigated through cyclic voltammetry, and the results indicate the lack of communication between the ferrocene units, because the separation between any two ferrocene units is greater than the 5-6 A range in both the free ligand and the helicates.
- Raja, Muthukrishna,Iyer, Ratnasabapathy G.,Gwengo, Chengeto,Reger, Daniel L.,Pellechia, Perry J.,Smith, Mark D.,Pascui, Andrea E.
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Read Online
- A porous supramolecular ionic solid
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We report a synthetic strategy to integrate discrete coordination cages into extended porous materials by decorating opposite charges on the singular cage, which offers multidirectional electrostatic forces among cages and leads to a porous supramolecular ionic solid. The resulting material is non-centrosymmetric and affords a piezoelectric coefficient of 8.19 pC N?1, higher than that of the wurtzite ZnO.
- Chen, Ying-Pin,Chen, Yu-Sheng,Gao, Wen-Yang,Jackson, Nathan,Vazquez, Irma Rocio
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supporting information
p. 7248 - 7251
(2021/07/28)
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- Design and synthesis of cage-like NADH model molecule intermediate with multi-chiral centers
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Studying NADH molecules is one of the most active areas in biomimetic research. It is important to design novel and efficient chiral NADH model molecules. Herein, a cage-like NADH model with multi-chiral centers was designed, and key intermediates have been synthesized. In this study, we found that pentafluorophenoxy group is an excellent leaving group for our synthetic route.
- Zhang, Tong,Bai, Cui-Bing,Wu, Yue-Hua,Wang, Nai-Xing,Xu, Bao-Cai,Yan, Zhan,Xing, Yalan
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supporting information
p. 410 - 416
(2019/02/05)
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- The flexibility-complementarity dichotomy in receptor-ligand interactions
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Synthetic supramolecular complexes provide an opportunity for quantitative systematic exploration of the relationship between chemical structure and molecular recognition phenomena. A family of closely related zinc porphyrin-pyridine complexes was used to examine the interplay of conformational flexibility and geometric complementarity in determining the selectivity of molecular recognition events. The association constants of 48 zinc porphyrin-pyridine complexes were measured in two different solvents, toluene and 1,1,2,2-tetrachloroethane (TCE). These association constants were used to construct 32 chemical double mutant cycles to dissect the free energy contributions of intramolecular H-bonds between the phenol side arms of the porphyrins and the ester or amide side arms of the pyridine ligands. Effective molarities (EM) for the intramolecular interactions were determined by comparison with the corresponding intermolecular H-bonding interactions. The values of EM do not depend on the solvent and are practically identical for amide and ester H-bond acceptors located at the same site on the ligand framework. However, there are variations of an order of magnitude in EM depending on the flexibility of the linker used to connect the H-bond acceptors to the pyridine ligands. Rigid aromatic linkers give values of EM that are an order of magnitude higher than the values of EM for the corresponding ester linkers, which have one additional torsional degree of freedom. However, the most flexible ether linkers give values of EM that are also higher than the values of EM for the corresponding ester linkers, which have one less torsional degree of freedom. Although the penalty for conformational restriction on binding is higher for the more flexible ether linkers, this flexibility allows optimization of the geometric complementarity of the ligand for the receptor, so there is a trade off between preorganization and fit.
- Sun, Hongmei,Hunter, Christopher A.,Llamas, Eva Marina
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p. 1444 - 1453
(2015/02/19)
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- Electron-deficient heteroarenium salts: An organocatalytic tool for activation of hydrogen peroxide in oxidations
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A series of monosubstituted pyrimidinium and pyrazinium triflates and 3,5-disubstituted pyridinium triflates were prepared and tested as simple catalysts of oxidations with hydrogen peroxide, using sulfoxidation as a model reaction. Their catalytic efficiency strongly depends on the type of substituent and is remarkable for derivatives with an electron-withdrawing group, showing reactivity comparable to that of flavinium salts which are the prominent organocatalysts for oxygenations. Because of their high stability and good accessibility, 4-(trifluoromethyl)pyrimidinium and 3,5-dinitropyridinium triflates are the catalysts of choice and were shown to catalyze oxidation of aliphatic and aromatic sulfides to sulfoxides, giving quantitative conversions, high preparative yields and excellent chemoselectivity. The high efficiency of electron-poor heteroarenium salts is rationalized by their ability to readily form adducts with nucleophiles, as documented by low pKR+ values (pKR+ red > -0.5 V). Hydrogen peroxide adducts formed in situ during catalytic oxidation act as substrate oxidizing agents. The Gibbs free energies of oxygen transfer from these heterocyclic hydroperoxides to thioanisole, obtained by calculations at the B3LYP/6-311++g(d,p) level, showed that they are much stronger oxidizing agents than alkyl hydroperoxides and in some cases are almost comparable to derivatives of flavin hydroperoxide acting as oxidizing agents in monooxygenases.
- ?turala, Ji?í,Bohá?ová, Soňa,Chudoba, Josef,Metelková, Radka,Cibulka, Radek
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p. 2676 - 2699
(2015/03/18)
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- Oxidative activation of dihydropyridine amides to reactive acyl donors
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Amides of 1,4-dihydropyridine (DHP) are activated by oxidation for acyl transfer to amines, alcohols and thiols. In the reduced form the DHP amide is stable towards reaction with amines at room temperature. However, upon oxidation with DDQ the acyl donor is activated via a proposed pyridinium intermediate. The activated intermediate reacts with various nucleophiles to give amides, esters, and thio-esters in moderate to high yields. This journal is
- Funder, Erik Daa,Trads, Julie B.,Gothelf, Kurt V.
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p. 185 - 198
(2015/01/16)
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- Dissection of complex molecular recognition interfaces
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The synthesis of a family of zinc porphyrins and pyridine ligands equipped with peripheral H-bonding functionality has provided access to a wide range of closely related supramolecular complexes featuring between zero and four intramolecular H-bonds. An automated UV/vis titration system was used to characterize 120 different complexes, and these data were used to construct a large of number of different chemical double mutant cycles to quantify the intramolecular H-bonding interactions. The results probe the quantitative structure-activity relationship that governs cooperativity in the assembly of complex molecular recognition interfaces. Specifically, variations in the chemical structures of the complexes have allowed us to change the supramolecular architecture, conformational flexibility, geometric complementarity, the number and nature of the H-bond interactions, and the overall stability of the complex. The free energy contributions from individual H-bonds are additive, and there is remarkably little variation with architecture in the effective molarity for the formation of intramolecular interactions. Intramolecular H-bonds are not observed in complexes where they are geometrically impossible, but there are no cases where excellent geometric complementarity leads to very high affinities. Similarly, changes in conformational flexibility seem to have limited impact on the values of effective molarity (EM). The major variation that was found for all of the 48 intramolecular interactions that were examined using double mutant cycles is that the values of EM for intramolecular carboxylate ester-phenol H-bonds (200 mM) are an order of magnitude larger than those found for phosphonate diester-phenol H-bonds (30 mM). The corresponding intermolecular phosphonate diester-phenol H-bonds are 2 orders of magnitude more stable than carboxylate ester-phenol H-bonds, and the large differences in EM may be due to some kind of compensation effect, where the stronger H-bond is harder to make, because it imposes tighter constraints on the geometry of the complex.
- Hunter, Christopher A.,Misuraca, Maria Cristina,Turega, Simon M.
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supporting information; experimental part
p. 582 - 594
(2011/04/16)
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- Use of the curtius rearrangement of acryloyl azides in the synthesis of 3,5-disubstituted pyridines: Mechanistic studies
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A series of disubstituted pyridine derivatives was synthesized from the corresponding acryloyl azides by acetic acid-promoted cycloaddition. This represents a novel and convenient synthetic approach to the symmetric 3,5-disubstituted pyridines. The nature of the substituent on the double bond and the utilized solvent were found to be crucial to the yield of pyridines. The reactivity of the acid-promoted cycloaddition increases with the presence of aryl groups, such as phenyl and pyridinyl. We also explored the comprehensive mechanism by the acid-promoted cycloaddition of 13C-labeled cinnamoyl azide. The symmetric 3,5-disubstituted pyridines were synthesized from acryloyl azides by acetic acid-promoted trimolecular condensation.
- Chuang, Ta-Hsien,Chen, Yu-Chi,Pola, Someshwar
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experimental part
p. 6625 - 6630
(2010/11/18)
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- A novel NADH model: Design, synthesis, and its chiral reduction and fluorescent emission
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A novel chiral nicotinamide adenine dinucleotide hydrogen (NADH) model with C3 symmetry was designed and synthesized. Hydrogens at the C-4 position of all dihydropyridine rings in the inner part of the bowl could transfer to the substrate with powerful enantioselectivity. This novel C 3 symmetrical NADH model is capable of fluorescence emission at 455 nm when excited at 390 nm.
- Wang, Nai-Xing,Zhao, Jia
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scheme or table
p. 3045 - 3050
(2010/04/28)
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- Evidence for partially bound states in cooperative molecular recognition interfaces
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A zinc porphyrin equipped with four amide H-bonding sites provides a rigid molecular receptor for the study of cooperative multipoint binding interactions. The interaction of this receptor with a variety of pyridine ligands bearing zero, one, and two H-bonding sites has been studied using UV/vis absorption, 1H and 31P NMR spectroscopy, and isothermal titration calorimetry in five different solvents. The results are analyzed in terms of a bound state that populates an ensemble of different complexes in which zero, one, or two of the potential H-bond interactions are formed. The key parameter that determines the behavior of the system is the product of the association constant for the H-bond interaction, KH, and the effective molarity for the intramolecular interaction, EM. In the system reported here, EM is 0.1-1 M for all of the intramolecular interactions. For strong H-bonds (large K H in nonpolar solvents), all of the interactions are formed in the complex and the fully bound state dominates. In this case, additional binding interactions produce incremental increases in complex stability. However, for weaker H-bonds (small KH in polar solvents), the formation of additional interactions does not lead to an increase in the overall stability of the complex, due to the population of partially bound states.
- Chekmeneva, Elena,Hunter, Christopher A.,Turega, Simon M.,Packer, Martin J.
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experimental part
p. 17718 - 17725
(2009/07/10)
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- Inhibitors of 11-beta hydroxysteroid dehydrogenase type I
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Novel compounds are provided which are 11-beta-hydroxysteroid dehydrogenase type I inhibitors. 11-beta-hydroxysteroid dehydrogenase type I inhibitors are useful in treating, preventing, or slowing the progression of diseases requiring 11-beta-hydroxysteroid dehydrogenase type I inhibitor therapy. These novel compounds have the structure: or stereoisomers or prodrugs or pharmaceutically acceptable salts thereof, wherein G, L, Q, Z, R6, R7, and R8 are defined herein.
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Page/Page column 30
(2010/11/24)
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- Appending a tris-imidazole ligand with a Tyr244 mimic on the distal face of bromoacetamidoporphyrin
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(Equation presented) Bromoacetamidoporphyrin is a convenient synthon for the attachment of distal superstructures at room temperature in good yields. New models are presented that contain a tris-imidazole distal ligand set bound to the porphyrin in either a binary or trinary fashion. More importantly, one distal imidazole is cross-linked to a phenol mimicking Tyr244, making this model the closest structural analogue yet reported of the metal free cytochrome c oxidase (CcO) active site.
- Collman, James P.,Decreau, Richard A.,Costanzo, Simona
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p. 1033 - 1036
(2007/10/03)
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- Behavior of Pyridinium Salts Obtained from Derivatives of Pyridinedicarboxylic Acids in Basic Solutions. Addition of Hydroxide or Alkoxide To Form 1,2-Dihydropyridine Intermediates
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The N-alkylated pyridinium salts obtained from the diethyl esters, N-ethyl amides, and N,N-diethyl amides of pyridine-3,5-dicarboxylic acid exhibit ultraviolet absorptions of moderate intensity in the region of 350 nm when dissolved in 95percent ethanol.This absorption increases in intensity on addition of base and disappears on acidification of the solutions.It is not observed in rigorously dried solvents like chloroform or methylene chloride.By 1H NMR spectroscopy it has been shown that a 1,2-dihydropyridine is formed reversibly by addition of hydroxide (or methoxide) to the 2-position of the pyridinium salts.Concurrently with the formation of these intermediates, proton-deuterium exchange (in deuterated solvents) occurs, possibly via betaines formed by base-induced deprotonation at the 2-position of the pyridinium salts.The corresponding derivatives of pyridine-2,5- and -3,5-dicarboxylic acids do not display this behavior.
- Speelman, Johanna C.,Kellogg, Richard M.
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p. 647 - 653
(2007/10/02)
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- Brain-specific drug delivery
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The subject compounds, which are adapted for the site-specific/sustained delivery of centrally acting drug species to the brain, are: (a) compounds of the formula wherein [D] is a centrally acting drug species, and [DHC] is the reduced, biooxidizable, blood-brain barrier penetrating lipoidal form of a dihydropyridine pyridinium salt redox carrier, with the proviso that when [DHC] is STR1 wherein R is lower alkyl or benzyl and [D] is a drug species containing a single NH2 or OH functional group, the single OH group when present being a primary or secondary OH group, said drug species being linked directly through said NH2 or OH function group to the carbonyl function of [DHC], then [D] must be other than a sympathetic stimulant, steroid sex hormone or long chain alkanol; and (b) non-toxic pharmaceutically acceptable salts of compounds of formula (I) wherein [D] is a centrally acting drug species and [DHC] is the reduced, biooxidizable, blood-brain barrier penetrating lipoidal form of a dihydropyridine pyridinium salt redox carrier. The corresponding ionic pyridinium salt type drug/carrier entitles [D--QC]+ X- are also disclosed.
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- Brain-specific drug delivery
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The subject compounds, which are adapted for the site-specific/sustained delivery of centrally acting drug species to the brain, are: (a) compounds of the formula wherein [D] is a centrally acting drug species, and [DHC] is the reduced, biooxidizable, blood-brain barrier penetrating lipoidal form of a dihydropyridine pyridinium salt redox carrier, with the proviso that when [DHC] is STR1 wherein R is lower alkyl or benzyl and [D] is a drug species containing a single NH2 or OH functional group, the single OH group when present being a primary or secondary OH group, said drug species being linked directly through said NH2 or OH functional group to the carbonyl function of [DHC], then [D] must be other than a sympathetic stimulant, steroid sex hormone or long chain alkanol; and (b) non-toxic pharmaceutically acceptable salts of compounds of formula (I) wherein [D] is a centrally acting drug species and [DHC] is the reduced, biooxidizable, blood-brain barrier penetrating lipoidal form of a dihydropyridine pyridinium salt redox carrier. The corresponding ionic pyridinium salt type drug/carrier entities [D-QC]+ Y- are also disclosed.
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- PALLADIUM CATALYSED SYNTHESIS OF N AND S HETEROCYCLIC ESTERS
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Palladium catalysed alkoxycarbonylation of heterocyclic halides affords a simple and versatile synthesis of both N and S heterocyclic esters where a range of catalysts have been studied and a method to employ inexpensive inorganic bases has been found.
- Head, Robert A.,Ibbotson, Arthur
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p. 5939 - 5942
(2007/10/02)
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