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Pyrrole Ring (pyrrole + ring)
Selected AbstractsChemInform Abstract: Furan Ring Recyclization in 2-Furfurylthieno[2,3-b]pyridines: An Intramolecular N-Alkylation of Pyrrole Ring under Acid Conditions.CHEMINFORM, Issue 34 2010Darya Yu. Abstract Depending on reaction conditions, the new heterocycles (V) and (VII) are formed from the 4-unsubstituted derivative (IVa). [source] First Example of Construction of a Pyrrole Ring Bonded to a Steroid System by the Trofimov Reaction.CHEMINFORM, Issue 38 2002A. M. Vasil'tsov Abstract For Abstract see ChemInform Abstract in Full Text. [source] Chemo-, Regio- and Stereospecific Synthesis of Unnatural, Fluorescent Amino Acids by Condensation of L -Lysine and 1-Vinylpyrrole-2-carbaldehydesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 24 2010Andrey V. Ivanov Abstract A new family of unnatural, optically active amino acids containing the pyrrole moiety have been synthesized by condensation of 1-vinylpyrrole-2-carbaldehydes with L -lysine under mild conditions (EtOH, room temp., 2.5,3 h, 0.5 wt.-% of CF3CO2H) in up to 90,% yields. Unlike non-vinylated analogues, 1-vinylpyrrole-2-carbaldehydes react chemo-, regio- and stereospecifically with an ,-amino group only to afford products of exclusively (E) configuration. The amino acids synthesized containing aromatic or condensed aromatic substitutents in the pyrrole ring fluoresce in the UV/Vis region (,max = 350,382 nm, Stokes shifts 6150,7800 cm,1). [source] One-Pot Synthesis of Core-Modified Rubyrin, Octaphyrin, and Dodecaphyrin: Characterization and Nonlinear Optical PropertiesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 27 2007Rajeev Kumar Abstract Modified 26, rubyrin, 36, octaphyrin, and 54, dodecaphyrin systems have been synthesized in moderately good yields through acid-catalyzed condensations of terthiophene diols and tripyrranes. The product distributions are decided both by the acid catalyst concentration and by the nature of the meso substituents. For example, a new isomer of [26]hexaphyrin(1.1.1.1.0.0) (rubyrin) was obtained with 0.3 equiv. of p -toluenesulfonic acid, when the meso substituent was mesityl in at least one of the precursors. A change of the mesityl substituent for a p -methoxy substituent in terthiophene diol resulted in the formation of a [3,+,3,+,3,+,3] condensation product , [54]dodecaphyrin(1.1.1.1.0.0.1.1.1.1.0.0) , in addition to the expected rubyrin. Furthermore, an increase in the acid concentration to 0.6 equiv. resulted in the formation of a new [36]octaphyrin(1.1.1.1.1.1.0.0), in addition to the rubyrin and dodecaphyrin. A single-crystal X-ray analysis of octaphyrin represents the first example of a planar conformation of an octaphyrin with six meso links. In rubyrin 19, one thiophene ring, opposite to the terthiophene subunit, is inverted, while in octaphyrin 30 one pyrrole ring and two thiophene rings are inverted. The various conformational possibilities tested for the unsubstituted dodecaphyrin 28, at semiempirical level, suggest that the most stable conformation is a figure-eight. The final geometry optimization of figure-eight dodecaphyrin was done at the B3LYP/6-31G* level of DFT. Octaphyrins and dodecaphyrins bind trifluoroacetate anion effectively in their diprotonated forms, the binding constants (K) being 638 M,1 for dodecaphyrin 28, and 415 M,1 for octaphyrin 30. Electrochemical data reveal HOMO destabilization with increasing , electron conjugation, consistently with the large red shifts of the absorption bands. Preliminary studies on the use of these expanded porphyrins as third-order NLO materials were followed by measurements of their two-photon absorption (TPA) cross-sections [,(2)]. The ,(2) values increase upon going from the 26, rubyrins to the 54, dodecaphyrins, confirming our earlier observation that increases in ,-conjugated electrons increase the TPA values.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Phosphorylation of N -Silylpyrroles with Phosphorus TribromideHETEROATOM CHEMISTRY, Issue 1 2008Aleksandra A. Chaikovskaya Phosphorylation of N -trimethylsilyl- and N -dimethyl-tert-butylsilylpyrroles with phosphorus tribromide in pyridine proceeds selectively at position 3 of the pyrrole ring. Removal of the trialkylsilyl protecting group has furnished the first representatives of N -unsubstituted 3-phosphorylated pyrroles. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:93,96, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20416 [source] A New Approach to Pyrrolocoumarin Derivatives by Palladium-Catalyzed Reactions: Expedient Construction of Polycyclic Lamellarin ScaffoldADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2009Lei Chen Abstract A new and efficient protocol for straightforward synthesis of chromeno[3,4- b]pyrrol-4(3H)-one derivatives by palladium-catalyzed sequential coupling/cyclization reactions has been developed. The key strategy relies on creation of pyrrole ring through palladium-catalyzed intramolecular hydroamination of related acetylenic aminocoumarins. The synthetic utility of the obtained chromeno[3,4- b]pyrrol-4(3H)-one product has been demonstrated by the expedient synthesis of polycyclic lamellarin scaffold in four steps. It provides a new entry to synthesis of potentially valuable lamellarin analogues. [source] Reactivity studies of ethyl(Z)- N -(2-amino-1,2-dicyanovinyl) formimidate with carbonyl compounds in the presence of base,JOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 5 2000M. Joséalves The reaction of ethyl(Z)- N -(2-amino-1,2-dicyanovinyl)formimidate 6 with carbonyl compounds in the presence of triethyl amine occurs with formation of the Schiff s base and intramolecular hydrolysis of the adjacent cyano group to give the alkylideneamino derivatives 8a-f. When the ,-carbon of the ketone has at least one proton, the prolonged contact of 8a-f with triethylamine causes intramolecular cyclization between this carbon and the imidate carbon atom to form a seven membered ring. This is followed by cyclization of the cyano and amido groups, leading to the pyrrolo[4,3- b][1,4]diazepines 9. If a strong base is used the first ring to be formed is the pyrrole ring as evidenced in the reaction of 8a with 1,8-diazabicyclo[5.4.0]undec-7-ene leading to 14. The subsequent addition of methyl amine to the reaction mixture, caused cleavage of the alkylideneamino unit and formation of the amidine function from the imi date (15). The addition of acid to the imidates 8a and 8f led to the diazepine compounds 10a and 10f respectively. A suspension of compound 8e in ethanol and triethylamine evolved to a pyrazinone structure 12 under kinetic conditions (4 hours, room temperature) and to the pyrrolo[4,3- b][1,4]diazepine 9e under thermodynamic conditions (48 hours, room temperature). [source] Synthesis and nuclear magnetic resonance spectroscopic studies of 1-arylpyrrolesJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 1 2000Chang Kiu Lee A series of m - and p -substituted 1-phenyl, 1-benzyl, 1-benzoyl, and 1-(2-phenylethyl)pyrroles was prepared and their 1H and 13C nmr spectroscopic characteristics were examined. In general, good correlations were observed between the chemical shift values of the ,H and the ,C of pyrroles [except 1-(2-phenylethyl)pyrroles] and the Hammettt ,. The observation may be explained in terms of the electronic effects of the substituents which are transmitted through bonds and through space by interaction of the p orbitals between ,Cs of the pyrrole ring and m - and pCs of the phenyl ring. Substituent constants of 1-pyrrolyl, 1-pyrrolylmethyl, and 1-pyrroloyl groups for the 1H and 13C chemical shifts of phenyl ring are also presented. [source] Characterization of glass solutions of poorly water-soluble drugs produced by melt extrusion with hydrophilic amorphous polymersJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 3 2001Angus Forster Indomethacin, lacidipine, nifedipine and tolbutamide are poorly soluble in water and may show dissolution-related low oral bioavailability. This study describes the formulation and characterization of these drugs as glass solutions with the amorphous polymers polyvinylpyrrolidone (PVP) and polyvinylpyrrolidone-co-vinyl acetate by melt extrusion. The extrudates were compared with physical mixtures of drug and polymer. X-ray powder diffraction, thermal analysis, infrared spectroscopy, scanning electron microscopy, HPLC, moisture analysis and dissolution were used to examine the physicochemical properties and chemical stability of the glass solutions prepared by melt extrusion at a 1:1 drug/polymer ratio. Depending on the temperature used, melt extrusion produced amorphous glass solutions, with markedly improved dissolution rates compared with crystalline drug. A significant physicochemical interaction between drug and polymer was found for all extrudates. This interaction was caused by hydrogen bonding (H-bonding) between the carbonyl group of the pyrrole ring of the polymer and a H-donor group of the drug. Indomethacin also showed evidence of H-bonding when physical mixtures of amorphous drug and PVP were prepared. After storage of the extrudates for 4,8 weeks at 25°C/75% relative humidity (RH) only indomethacin/polymer (1:1) extrudate remained totally amorphous. All extrudates remained amorphous when stored at 25°C/< 10% RH. Differences in the physical stability of drug/polymer extrudates may be due to differences in H-bonding between the components. [source] Vibrational analysis of Ni(II)- and Cu(II)-octamethylchlorin by polarized resonance Raman and Fourier transform infrared spectroscopyJOURNAL OF RAMAN SPECTROSCOPY, Issue 6-7 2001Robert J. Lipski We measured the polarized resonance Raman spectra of Cu(II)-2,2,7,8,12,13,17,18-octamethylchlorin in CS2 at various excitation wavenumbers in a spectral region covering the Qy, Qx and Bx optical absorption bands. Additionally, we measured the FTIR-Raman spectrum of the highly overcrowded spectral region between 1300 and 1450 cm,1. The spectral decomposition was carried out by a self-consistent global fit to all spectra obtained. The thus identified Raman and IR lines were assigned by comparison with the resonance Raman spectra of Cu(II)-octaethylporphyrin, by utilizing their depolarization ratio dispersions and by a normal mode analysis. The latter was based on a modified transferable molecular mechanics force field of Ni(II)-octaethylporphyrin [E. Unger, M. Beck, R.J. Lipski, W. Dreybrodt, C.J. Medforth, K.M. Smith and R. Schweitzer-Stenner, J. Phys. Chem. B103, 10229 (1999)]. A comparison of normal mode patterns obtained for Cu(II)-octamethylchlorin and Cu(II)-octaethylporphyrin revealed that some modes are significantly distorted by the reduction of the pyrrole ring, in accordance with results which Boldt et al. reported earlier for Ni(II)-octaethylchlorin [N.J. Boldt, F.J. Donohoe, R.R. Birge and D.F. Bocian, J. Am. Chem. Soc.109, 2284 (1987)]. In contrast to conclusions drawn from this study, however, the results of our vibrational analysis and several further lines of evidence suggest that the normal modes of corresponding chlorines and porphyrins are still comparable, because they display contributions from the same local coordinates. Thus, the classical normal mode classification developed for metalloporphyrins is also applicable to metallochlorins. Finally, we performed a preliminary analysis of the absorption spectrum and the resonance excitation profiles and depolarization ratio dispersions of some Raman lines. The results show that the electronic properties of Cu(II)-octamethylchlorin can still be described in terms of Gouterman's four orbital model [M. Gouterman, J. Chem. Phys.30, 1139 (1959)]. In regions of the Q bands, Raman scattering of A1 modes is determined by interferences between Franck, Condon coupling and interstate Herzberg, Teller coupling between Qx(Qy) and Bx(By) states. The B2 modes are resonance enhanced by Herzberg, Teller coupling between Qx and Qy and between Qx(Qy) and By(Bx). Franck, Condon coupling of A1 modes with large contributions from C,Cm stretching vibrations is comparatively strong for Qx. This is interpreted as reflecting the expansion of the chlorin macrocycle by an electronic transition into this excited state. Copyright © 2001 John Wiley & Sons, Ltd. [source] Phototoxicity of Protoporphhyrin IX, Diarginine Diprotoporphyrinate and N,N-Deiphenylalanyl Protoporphyrin Toward Human Fibroblasts and ketratinocytes In vitro: Effect of 5-Methoxypsoralen,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 3 2004Andrzej Bugaj The phototoxicity of two new porphyrin photosensitizers, diarginine diprotoporphyrinate (PP(Arg)2) and N,N -diphenylalanyl protoporphyrin (PP(Phe)2), and the synergistic effect of 5-methaoxyposralen (5-MOP) have been studied in comparison with that of protoporphyrin IX (PPIX). Under ultraviolet A (UV-A) irradiation (,= 365 nm), the phototoxicity of the porphyrins toward cultured human fibroblasts and keratino-cytes decerases in the order: PPIX > PP(Arg)2 > PP(Phe)2. A synergistic efect of 5-MOP on the phototoxicity of PPIX, PP(Arg)2 and PP(Phe)2 has been observed. The combination of PPIX, PP(Arg)2 and PP(Phe)2 with 0.1,0.5 ,M 5-MOP significantly potentiates the phototoxicity of the three porphyrins. The most effective potentiation was observed with the water-soluble PP(Arg)2 and 5-MOP concentrations lowere than 0.75 ,M. Above this 5-MOP concnetration this potentiation is abolished. The intracellular concentration of PPIX and PP(Phe)2 is independent of the presence of 5-MOP. On the other hand, the intracellular contnet of PP(Arg)2 is decerased in concentration-dependent manner by the psoralen. Illumination with red light, not absorbed by 5-MOP, leads to a weak potentiation of the PP(Arg)2 phototoxic effect in the presence of 5-MOP, suggesting that dark interaction of 5-MOP with cell membranes aggravated by porphyrin photosensitization is involved in the observed phenomena. The results are tentatively explained by differences in hydrophobicity and molecular structure of the examined photosensitizers. PPIX, which is barely soluble in water, has a significantly higher affinity for cell membranes and simultaneously exerts a stronger phototoxic effect than PP(Arg)2 whose solubility in water is high. On the other hand, the weak phototoxicity of PP(Phe)2 could be explained by the steric hindrance brought by the phenylalanyl substituents on the pyrrole ring. The loss in the PP(Arg)2 cell content probably explains the inhibition of the synergistic effect of 5-MOP on the PP(Arg)2 phototoxicity at high 5-MOP concentration. This study suggests that PP(Arg)2 in combinatin with 5-MOP might reveal a strong phototoxic effect when applied to skin cancer treatment. [source] Electrospray tandem mass spectrometry of lexitropsinsRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 12 2001M. Rosário M. Domingues Several compounds, representative of the class of lexitropsins, were analyzed by electrospray tandem mass spectrometry. The study of the fragmentations of the protonated molecular species ([M,+,H]+) and of selected fragment ions allowed proposals for the main fragmentation pathways of compounds of this type. The interpretation of the fragmentation pathways of these compounds was complicated because of intramolecular hydrogen migration. In order to better understand the fragmentation pathways, the MS/MS/MS spectra of several compounds, and the MS/MS and MS/MS/MS spectra of the deuterated compounds, were obtained. Accurate mass measurements helped elucidate the structures of smaller fragment ions. Low-energy collision-induced decomposition (CID) tandem mass spectrometry of lexitropsins with electrospray ionization has proven to be a good method for the structural characterization and identification of this class of compounds. Main fragmentation pathways occur by cleavage of the peptide bond followed by the elimination of the substituted pyrrole ring, and their elucidation will facilitate structural characterization of new lexitropsins. Copyright © 2001 John Wiley & Sons, Ltd. [source] 5-Hydroxyalkyl derivatives of tert -butyl 2-oxo-2,5-dihydro-1H -pyrrole-1-carboxylate: diastereoselectivity of the Mukaiyama crossed-aldol-type reactionACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2009Olivier Vallat The title compounds, rac -(1,R,2R)- tert -butyl 2-(1,-hydroxyethyl)-3-(2-nitrophenyl)-5-oxo-2,5-dihydro-1H -pyrrole-1-carboxylate, C17H20N2O6, (I), rac -(1,S,2R)- tert -butyl 2-[1,-hydroxy-3,-(methoxycarbonyl)propyl]-3-(2-nitrophenyl)-5-oxo-2,5-dihydro-1H -pyrrole-1-carboxylate, C20H24N2O8, (II), and rac -(1,S,2R)- tert -butyl 2-(4,-bromo-1,-hydroxybutyl)-5-oxo-2,5-dihydro-1H -pyrrole-1-carboxylate, C13H20BrNO4, (III), are 5-hydroxyalkyl derivatives of tert -butyl 2-oxo-2,5-dihydropyrrole-1-carboxylate. In all three compounds, the tert -butoxycarbonyl (Boc) unit is orientated in the same manner with respect to the mean plane through the 2-oxo-2,5-dihydro-1H -pyrrole ring. The hydroxyl substituent at one of the newly created chiral centres, which have relative R,R stereochemistry, is trans with respect to the oxo group of the pyrrole ring in (I), synthesized using acetaldehyde. When a larger aldehyde was used, as in compounds (II) and (III), the hydroxyl substituent was found to be cis with respect to the oxo group of the pyrrole ring. Here, the relative stereochemistry of the newly created chiral centres is R,S. In compound (I), O,H...O hydrogen bonding leads to an interesting hexagonal arrangement of symmetry-related molecules. In (II) and (III), the hydroxyl groups are involved in bifurcated O,H...O hydrogen bonds, and centrosymmetric hydrogen-bonded dimers are formed. The Mukaiyama crossed-aldol-type reaction was successful when using the 2-nitrophenyl-substituted hydroxypyrrole, or the unsubstituted hydroxypyrrole, and boron trifluoride diethyl ether as catalyst. The synthetic procedure leads to a syn configuration of the two newly created chiral centres in all three compounds. [source] Crystallization and preliminary crystallographic studies of human indoleamine 2,3-dioxygenaseACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 3 2006Shun-ichiro Oda Indoleamine 2,3-dioxygenase (IDO) is a haem-containing dioxygenase that catalyzes the oxidative cleavage of the pyrrole ring of indoleamines by the insertion of molecular oxygen. This reaction is the first and the rate-limiting step in the kynurenine pathway, the major Trp catabolic pathway in mammals. Recombinant human IDO was crystallized by the vapour-diffusion technique. The addition of 4-phenylimidazole as a haem ligand was essential for crystallization. The crystals belong to space group P212121, with unit-cell parameters a = 86.1, b = 98.0, c = 131.0,Å. Diffraction data were collected to 2.3,Å resolution. [source] The First General and Selective Palladium(II)-Catalyzed Alkoxycarbonylation of Arylboronates: Interplay among Benzoquinone-Ligated Palladium(0) Complex, Organoboron, and Alcohol SolventADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 2-3 2010Yoshihiko Yamamoto Abstract Methoxycarbonylation of aryl- and alkenylboron compounds was performed using the palladium(II) acetate/triphenylphosphine [Pd(OAc)2/PPh3] catalyst with p -benzoquinone as a stoichiometric oxidant in methanol at ambient temperature to obtain the corresponding methyl esters in good yields. A wide variety of functional groups including various carbonyl functionalities, nitrile, nitro, sulfone, and unprotected pyrrole rings were tolerated in the methoxycarbonlation, while the use of higher alcohols except for tert -butanol afforded various p -chlorobenzoates in moderate to high yields. The catalytic alkoxycarbonylation proceeded without any acid or base additive, and an oxidative transmetalation step is proposed to explain the exceptional efficacy of this protocol. DFT and MP2 calculations support the proposed mechanism. [source] Molecular Dynamics Simulations of the Orientation and Reorientational Dynamics of Water and Polypyrrole Rings as a Function of the Oxidation State of the PolymerMACROMOLECULAR THEORY AND SIMULATIONS, Issue 1 2005Jose J. López Cascales Abstract Summary: Polypyrrole is one of the most widely-studied conducting polymers due to its steady electrochemical response and good chemical stability in different solvents, including organic and inorganic ones. In this work, we provide for the first time valuable information in atomic detail concerning the steady and dynamic properties of pyrrole rings as a function of the oxidation state of the polymer. The study was carried out by Classical molecular dynamics simulation, where the system was modelled by 256 polypyrrole chains of 10 pyrrole rings each. Water was explicitly introduced in our simulations. Besides the uncharged or reduced state, two steady oxidation states of the polymer have been simulated by introducing a net charge (+1) on 85 and 256 of the polypyrrole chains. To balance the charges emerging in these oxidised states, 85 and 256 chloride ions (Cl,1) respectively, were introduced into the system. From an analysis of the simulated trajectories, the orientation and relaxation times of water and pyrrole rings were evaluated for the different oxidation states of the polymer across the polypyrrole/water interface. The calculated densities for different oxidation states describe the swelling or shrinking process during electrochemical oxidation or reduction respectively. The rotational relaxation times calculated for the polypyrrole rings decrease with increasing oxidation of the polymer, which is in a good agreement with experimental electrochemical data. Almost no variation in pyrrole ring orientation was measured for the different oxidation states of the polymer, even compared with polypyrrole bulk. As regards the water structure in the vicinity of the polypyrrole/water interface, both the orientation and orientation relaxation time were strongly affected by the presence of charges in the polymer. Thus, the water dipole was strongly orientated in the vicinity of the water/polypyrrole interface and its orientational relaxation time increased by one order of magnitude compared with bulk water, even when only one-third of the total polymer chains were oxidised. The results attained in this work were validated with experimental results, when they were available. Polypyrrole ring orientation and water orientation at the polypyrrole/water interface. (a) 256 rPPy and (b)171 rPPy,+,85 oPPy. [source] Low-temperature study of 3-acetylindole at 110,KACTA CRYSTALLOGRAPHICA SECTION C, Issue 7 2008Barbara Hachu The title compound, C10H9NO, contains an acetyl group that is nearly coplanar with the indole ring system, with an angle between the planes of the heterocyclic ring and the acetyl group of 1.75,(17)°. The planes of the benzene and pyrrole rings in the indole system make a dihedral angle of 2.05,(11)°. Each molecule in the unit cell is linked through N,H...O hydrogen bonds to two other molecules, forming hydrogen-bonded chains in the [101] direction with graph set C(6). The significance of this study lies in the analysis of the interactions occurring via hydrogen bonds in this structure, as well as in the comparison drawn between the molecular structure of the title compound and those of several other indole derivatives possessing a 3-carbonyl group. The correlation between the IR spectrum of this compound and the structural data is also discussed. [source] Expanding Sapphyrin: Towards Selective Phosphate BindingCHEMISTRY - A EUROPEAN JOURNAL, Issue 29 2008Evgeny Abstract The anion-templated syntheses and binding properties of novel macrocyclic oligopyrrole receptors in which pyrrole rings are linked through amide or imine bonds are described. The efficient synthesis was accomplished by anion-templated [1+1] Schiff-base condensation and acylation macrocyclization reactions. Free receptors and their host,guest complexes with hydrochloric acid, acetic acid, tetrabutylammonium chloride, and hydrogen sulfate were analyzed by single-crystal X-ray diffraction analysis. Stability constants with different tetrabutylammonium salts of inorganic acids were determined by standard 1H,NMR and UV/Vis titration techniques in [D6]DMSO/0.5,% water solution. According to the titration data, receptors containing three pyrrole rings (10 and 12) exhibit high affinity (log,Ka=5,7) for bifluoride, acetate, and dihydrogen phosphate, and interact weakly with chloride and hydrogen sulfate. The amido-bipyrrole receptors 11 and 13 with four pyrrole rings exhibit 104 - and 102 -fold selectivity for dihydrogen phosphate, respectively, as inferred from competitive titrations in the presence of tetrabutylammonium acetate. [source] | |||||||||||||||||||||||||