Distribution by Scientific Domains
Distribution within Chemistry

Selected Abstracts

Synthesis, Photophysical, and Electroluminescent Device Properties of Zn(II)-Chelated Complexes Based on Functionalized Benzothiazole Derivatives

Soo-Gyun Roh
Abstract New Zn(II)-chelated complexes based on benzothiazole derivatives, including substituted functional groups such as methyl (MeZn), methoxy (MeOZn), or fluorenyl unit (FuZn), are investigated to produce white-light emission. 2-(2-Hydroxyphenyl)benzothiazole derivatives in toluene and DMSO exhibit excited-state intramolecular proton transfer (ESIPT), leading to a large Stokes shift of the fluorescence emission. However, in methanol they exhibit no ESIPT due to the intermolecular hydrogen bonding between the 2-(2-hydroxyphenyl)benzothiazole derivative and methanol. Their Zn(II)-chelated complexes exhibit the absorption band red-shifted at 500,nm in nonpolar solvent and the absorption band blue-shifted at about 420,nm in protic solvent. In multilayer electroluminescent devices, methyl-substituted Zn(II)-chelated complex (MeZn) exhibits excellent power efficiency and fluorene-substituted Zn(II)-chelated complex (FuZn) has a high luminance efficiency (1,cd,m,2 at 3.5,V, 10,400,cd,m,2 at 14,V). The EL spectra of Zn(II)-chelated complexes based on benzothiazole derivatives exhibit broad emission bands. In addition, their electron-transport property for red,green,blue (RGB) organic light-emitting diodes (OLEDs) is systematically studied, in comparison with that of Alq3. The results demonstrate the promising potential of MeZn as an electron-transporting layer (ETL) material in preference to Alq3, which is widely used as an ETL material. [source]

4-(2-Hydroxyphenyl)-2-phenyl-2,3-dihydro-1H -1,5-benzodiazepine and the 2-(2,3-dimethoxyphenyl)-, 2-(3,4-dimethoxyphenyl)- and 2-(2,5-dimethoxyphenyl)-substituted derivatives

Carlos A. Escobar
The 1,5-benzodiazepine ring system exhibits a puckered boat-like conformation for all four title compounds [4-(2-hydroxyphenyl)-2-phenyl-2,3-dihydro-1H -1,5-benzodiazepine, C21H18N2O, (I), 2-(2,3-dimethoxyphenyl)-4-(2-hydroxyphenyl)-2,3-dihydro-1H -1,5-benzodiazepine, C23H22N2O3, (II), 2-(3,4-dimethoxyphenyl)-4-(2-hydroxyphenyl)-2,3-dihydro-1H -1,5-benzodiazepine, C23H22N2O3, (III), and 2-(2,5-dimethoxyphenyl)-4-(2-hydroxyphenyl)-2,3-dihydro-1H -1,5-benzodiazepine, C23H22N2O3, (IV)]. The stereochemical correlation of the two C6 aromatic groups with respect to the benzodiazepine ring system is pseudo-equatorial,equatorial for compounds (I) (the phenyl group), (II) (the 2,3-dimethoxyphenyl group) and (III) (the 3,4-dimethoxyphenyl group), while for (IV) (the 2,5-dimethoxyphenyl group) the system is pseudo-axial,equatorial. An intramolecular hydrogen bond between the hydroxyl OH group and a benzodiazepine N atom is present for all four compounds and defines a six-membered ring, whose geometry is constant across the series. Although the molecular structures are similar, the supramolecular packing is different; compounds (I) and (IV) form chains, while (II) forms dimeric units and (III) displays a layered structure. The packing seems to depend on at least two factors: (i) the nature of the atoms defining the hydrogen bond and (ii) the number of intermolecular interactions of the types O,H...O, N,H...O, N,H...,(arene) or C,H...,(arene). [source]

Synthesis, spectral and antimicrobial studies of diorganotin(IV)3(2,-hydroxyphenyl)-5-(4-substituted phenyl) pyrazolinates

U. N. Tripathi
Abstract Diorganotin(IV) dipyrazolinates of the type R2Sn(C15H12N2OX)2 [where C15H12N2OX = 3(2,-Hydroxyphenyl)-5(4-X-phenyl)pyrazoline {where X = H (a); CH3 (b); OCH3 (c); Cl (d) and R = Me, Prn and Ph}] have been synthesized by the reaction of R2SnCl2 with sodium salt of pyrazolines in 1:2 molar ratio, in anhydrous benzene. These newly synthesized derivatives have been characterized by elemental analysis (C, H, N, Cl and Sn), molecular weight measurement as well as spectral [IR and multinuclear NMR (1H, 13C and 119Sn)] studies. The bidentate behaviour of the pyrazoline ligands was confirmed by IR, 1H and 13C NMR spectral data. A distorted trans -octahedral structure around tin(IV) atom for R2Sn(C15H12N2OX)2 has been suggested. The free pyrazoline and diorganotin(IV) dipyrazolinates have also been screened for their antibacterial and antifungal activities. Some diorganotin(IV) dipyrazolinates exhibit higher antibacterial and antifungal effect than free ligand and some of the antibiotics. Copyright 2006 John Wiley & Sons, Ltd. [source]

Crystal structure of 2-(2'-hydroxyphenyl)-6-tributylstannyl-4-(3H )-quinazolinone and 2-(2'-hydroxyphenyl)-6-iodo-4-(3H)-quinazolinone

Ketai Wang
Abstract The structures of the title compounds C26H37N2O2Sn (I) and C14H9IN2O2 (II) were determined by single-crystal X-ray diffraction technique. Compound I crystallizes in the triclinic space group P1 with a = 9.560(3) , b = 16.899(6) , c = 17.872(5) , , = 65.957(7), , = 83.603(5), , ( = 75.242(5), V = 2549.8(13) 3, Z = 4, and D =1.374 g/cm3. The compound consists of a quinazolinone ring with phenol and tributylstannyl moieties. Compound II crystallizes in the monoclinic space group P21/c with a = 7.6454(12) , b = 5.9270(9) , c = 27.975(4) ; , = 90, , = 95.081(3), , = 90, V = 1262.7(3) 3, Z = 4, and D = 1.915 g/cm3. The compound consists of a quinazolinone ring with phenol and iodine substituents. For both I and II, the short intramolecular O,H,N and two long intermolecular N,H,O hydrogen bonds are highly effective in holding the molecular system in a stable state. ( 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Differential binding of endogenous steroids and chemicals to androgen receptors in rainbow trout and goldfish

Kelly Wells
Abstract Androgen receptors (ARs) from fish were characterized in order to evaluate differences in the binding affinities of steroids and environmental chemicals between mammals and fish, among species offish, and among target tissues within a species of fish. High-affinity, low-capacity ARs were identified in cytosolic fractions of rainbow trout brains (Oncorhynchus mykiss) and the brains, ovaries, and testes of goldfish (Carassius auratus) using [3H]testosterone. The binding specificities of endogenous steroids to the ARs did not differ between goldfish tissues but did differ between goldfish and rainbow trout. Interspecies differences in binding specificities were also seen using cyproterone acetate, which bound to the ARs in the goldfish tissues, but not in the rainbow trout brains. The mammalian antiandrogens flutamide, vinclozolin and its metabolites 2-(((3,5)-dichlorophenyl-carbamo-yl)oxy)-2-methyl-3-butenoic acid and 3,,5,-dichloro-2-hydroxy-2-methylbut-3-enanilide, along with procymidone did not bind to the ARs in any of the fish tissues tested. However, other mammalian antiandrogens including methoxychlor and its metabolite 2,2-bis(p -hydroxyphenyl)-1,1,1-trichloroethane, o,p,-DDT, o,p,-dichlorodiphenyldichloroethylene (DDE) and p,p,-DDE did bind to the fish ARs, but only in the goldfish testes, demonstrating tissue differences in AR binding specificities of environmental chemicals. These results may be due to the presence of multiple AR isoforms in the different fish species and tissues. This study supports the growing evidence of species differences in the potency and actions of endocrine-disrupting chemicals and suggests that multiple species need to be tested when screening the receptor binding ability of potential endocrine-disrupting chemicals. [source]

[CuII4] Clusters From the Self-Assembly of Two Imidazolidinyl 2-Phenolate-Bridged [CuII2] Units: The Role of the Chloride Bridge

Alok Ranjan Paital
Abstract A new family of tetracopper clusters [Cu4(,4 -X)L2]ClO4nH2O (1a,c) [X = Cl, Br, I; n = 12, 2, 2; H3L = 2-(2,-hydroxyphenyl)-1,3-bis[4-(2-hydroxyphenyl)-3-azabut-3-enyl]-1,3-imidazolidine] have been synthesised and characterised. The X-ray crystal structure of 1a reveals that the template action of the spherical Cl, anion (,4 -Cl,), which features a unique rectangular planar bridging mode, is responsible for the self-assembly of two [Cu2L]+ units in complex 1a. In this family of complexes the spherical halides serve as templates to assemble the dimeric unit into tetrameric complexes, which gives an insight into the role of the halide bridge in tetranuclear complex formation. The capacity of this bridge to mediate magnetic coupling has been examined by bulk magnetic measurements for complex 1a. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

Synthesis and Binding Properties of Dendritic Oxybathophenanthroline Ligands towards Copper(II)

Holger Stephan
Abstract Dendritic oxybathophenanthroline ligands (generation 0 to 3) have been synthesized by treatment of 4,7-bis(4,-hydroxyphenyl)-1,10-phenanthroline with the corresponding Frchet-type dendrons carrying a benzylic bromide function at the focal point. The complexation of copper(II) has been studied by liquid,liquid extraction using the radioisotope 64Cu and time-resolved laser-induced fluorescence spectroscopy (TRLFS) in organic media indicating the formation of 1:3 complexes (Cu:dendritic ligand). Electronic and EPR spectroscopy were used to characterize the copper(II) chromophore, which is shown to have the expected distorted square-planar geometry with two phenanthroline donors coordinated to the copper(II) center. The third dendritic ligand therefore is proposed to be bound by secondary interactions. The stability constants of the 1:3 complexes were found to be in the order of log K , 16 in CHCl3. On the other hand, increasing generation of the dendritic Frchet-type branches leads to enhanced shielding of the copper ion from the environment. Additional information about this behaviour was obtained by the fluorescence lifetimes, which are much less influenced upon addition of copper(II) salt to solutions of the higher generation ligands. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]

Cobalt(II) Complexes with Substituted Salen-Type Ligands and Their Dioxygen Affinity in N,N -Dimethylformamide at Various Temperatures

Andreas Huber
Abstract Several unsymmetrically substituted salen-type cobalt(II) Schiff-base complexes CoL [H2L = 1,6-bis(2-hydroxyphenyl)-3,3-dimethyl-2,5-diaza-1,5-hexadiene (1); 1,6-bis(2-hydroxyphenyl)-3,3-dimethyl-2,5-diaza-1,5-heptadiene (2); 1-(3- tert -butyl-2-hydroxy-5-methylphenyl)-6-(2-hydroxyphen-yl)-3,3-dimethyl-2,5-diaza-1,5-heptadiene (3); 1-(2-hydroxyphenyl)-6-methyl-2,5-diaza-1,5-nonadien-8-one (4); 1-(3- tert -butyl-2-hydroxy-5-methylphenyl)-6-methyl-2,5-di-aza-1,5-nonadien-8-one (5); 1-(2-hydroxyphenyl)-3,3,6-trimethyl-2,5-diaza-1,5-nonadien-8-one (6); 1-(3- tert -butyl-2-hydroxy-5-methylphenyl)-3,3,6-trimethyl-2,5-diaza-1,5-nonadien-8-one (7)] were prepared and characterized by their UV/Vis absorption spectra, magnetic moments, and oxidation potentials. Except for complex 4 (irreversible oxidation with t , 3 h), complexes 1,3 and 5,7 are remarkably resistant against irreversible auto-oxidation in air-saturated N,N -dimethylformamide (DMF) at ambient temperature. To characterize the Lewis acidity of the cobalt center in 1,7, the equilibrium constant Kpy was determined for monoadduct formation with pyridine (CoL + pyCoLpy). An O2 -sensitive optode was used to determine the Henry constant, KH, for the system O2/DMF in the temperature range 298,228 K. The formation of 1:1 adducts of complexes 1,7 with O2 in DMF, as characterized by the equilibrium constant K, was followed spectrophotometrically in the temperature range 298,228 K. The parameters ,Ho, ,So, and K are reported. At 298 K, K ranges from 21.9 M,1 (5) to 155 M,1 (7). The overall spectroscopic information, including EPR spectra obtained with frozen solutions of 3 and 7 in O2 -saturated DMF, confirm that the 1:1 adducts CoLO2 are cobalt(III) superoxo compounds. The symmetrically substituted salen complex8 [H2L = 1,6-bis(3- tert -butyl-2-hydroxy-5-methylphenyl)-3,3,4,4-tetramethyl-2,5-diaza-1,5-hexadiene in 8] is shown to catalyze the oxidation of triphenylphosphane and 2,6-di- tert -butylphenol by O2 in DMF at ambient temperature. The correlation of the data obtained for K, Kpy, and the oxidation potential E is discussed. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]

Syntheses of O6 -Alkyl- and Arylguanine Derivatives: Nucleobase Adducts Derived from Styrene 7,8- and 3,4-Oxides

Jan Novk
Abstract A series of O6 -alkyl and -arylguanine derivatives that may be formed in vivo after exposure to styrene has been prepared by reaction of 6-(4-aza-1-azoniabicyclo[2.2.2]octyl)-purine with alkoxides and aryloxides, respectively. Themonoprotected diols 2-allyloxy- or 2-benzyloxy-1-phenylethanol and 2-allyloxy- or 2-benzyloxy-2-phenylethanol were used as synthetic equivalents of styrene 7,8-oxide. 4-Vinylphenol, 2-(4-hydroxyphenyl)ethanol and 4-hydroxyphenylacetic acid were used as synthetic equivalents of arene oxide metabolites of styrene, i.,e., styrene 3,4-oxide, 4-(2-hydroxyethyl)benzene 1,2-oxide and 4-carboxymethylbenzene 1,2-oxide, respectively. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]

3(5)-(2-Hydroxyphenyl)-5(3)-styrylpyrazoles: Synthesis and Diels,Alder Transformations

Vera L. M. Silva
Abstract Reactions between cinnamoyl(2-hydroxybenzoyl)methanes and hydrazine hydrate in acetic acid gave 3-(2-hydroxyphenyl)-5-styrylpyrazoles, while the corresponding reactions with phenylhydrazine yielded 5-(2-hydroxyphenyl)-1-phenyl-3-styrylpyrazoles as the major products and 3-(2-hydroxyphenyl)-1-phenyl-5-styrylpyrazoles as by-products. The reaction mechanism of this transformation is discussed. The first cycloaddition reactions between ortho -benzoquinodimethane and either 3-(2-hydroxyphenyl)-5-styrylpyrazoles or 5-(2-hydroxyphenyl)-1-phenyl-3-styrylpyrazoles afforded 5-[2-(3-aryl-1,2,3,4-tetrahydronaphthyl)]-3-(2-hydroxyphenyl)pyrazoles or 3-[2-(3-aryl-1,2,3,4-tetrahydronaphthyl)]-1-phenyl-5-(2-hydroxyphenyl)pyrazoles, respectively. These cycloadducts were converted into the corresponding naphthylpyrazoles by oxidation with DDQ in dry 1,4-dioxane. The structures of all new derivatives have been established by NMR spectroscopy. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

Synthesis, Photophysical, and Electroluminescent Device Properties of Zn(II)-Chelated Complexes Based on Functionalized Benzothiazole Derivatives

Soo-Gyun Roh
Abstract New Zn(II)-chelated complexes based on benzothiazole derivatives, including substituted functional groups such as methyl (MeZn), methoxy (MeOZn), or fluorenyl unit (FuZn), are investigated to produce white-light emission. 2-(2-Hydroxyphenyl)benzothiazole derivatives in toluene and DMSO exhibit excited-state intramolecular proton transfer (ESIPT), leading to a large Stokes shift of the fluorescence emission. However, in methanol they exhibit no ESIPT due to the intermolecular hydrogen bonding between the 2-(2-hydroxyphenyl)benzothiazole derivative and methanol. Their Zn(II)-chelated complexes exhibit the absorption band red-shifted at 500,nm in nonpolar solvent and the absorption band blue-shifted at about 420,nm in protic solvent. In multilayer electroluminescent devices, methyl-substituted Zn(II)-chelated complex (MeZn) exhibits excellent power efficiency and fluorene-substituted Zn(II)-chelated complex (FuZn) has a high luminance efficiency (1,cd,m,2 at 3.5,V, 10,400,cd,m,2 at 14,V). The EL spectra of Zn(II)-chelated complexes based on benzothiazole derivatives exhibit broad emission bands. In addition, their electron-transport property for red,green,blue (RGB) organic light-emitting diodes (OLEDs) is systematically studied, in comparison with that of Alq3. The results demonstrate the promising potential of MeZn as an electron-transporting layer (ETL) material in preference to Alq3, which is widely used as an ETL material. [source]

Phosphorus heterocycles from 2-(2-hydroxyphenyl)-1H -benzimidazole

Julio Hernndez-Daz
Sixteen different P(III) and P(V) heterocycles derived from 2-(2-hydroxyphenyl)-1H-benzimidazole (1) are reported. In these heterocycles the phosphorus atom is part of a six-membered unsaturated ring. They were mainly studied by multinuclear NMR. The X-ray diffraction of 3,4- benzimidazole-5,6-benzo-2-dimethylamino-2-seleno- 1,3,2-oxazaphosphorinane is reported. Phosphoranes derived from 1 and 3,5-di-tert-butylcatechol, and bearing Cl, NMe2, or phenyl as substituent at phosphorus are presented. 2004 Wiley Periodicals, Inc. Heteroatom Chem 15:307,320, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20021 [source]

Phenylarsenic(III) complexes of 2-(2-hydroxyphenyl)benzothiazolines

Simpal Sharma
Equimolar reactions of PhAs(OMe)2 (prepared in situ) and 2-(2-hydroxyphenyl)benzothiazolines LH2 give the addition products PhAs(OMe)2LH2, while equimolar reactions of PhAsCl2 with Na2L yield substitution products PhAsL. All these derivatives have been characterized by elemental analyses and their plausible structures have been established on the basis of physico-chemical, IR, and NMR (1H and 13C) spectral studies. 2003 Wiley Periodicals, Inc. 15:92,96, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/.10220 [source]

Copper-Catalyzed Three-Component Synthesis of 2-Iminodihydrocoumarins and 2-Iminocoumarins

Yang Shen
Abstract An efficient synthesis of N -sulfonyl-substituted 2-imino-3,4-dihydrocoumarins and 2-iminocoumarins via a copper-catalyzed multicomponent reaction of sulfonyl azides with terminal alkynes and ,-(ortho -hydroxyphenyl)-,,,-unsaturated ketones or ortho -hydroxyphenylpropiolates has been developed. The cascade process involves trapping the keteimine by a nucleophilic addition and an intramolecular Michael addition. This methodology could well be extended to the concise synthesis of the polysubstituted piperidine scaffold. [source]

Use of chitosan for removal of bisphenol A and bisphenol derivatives through tyrosinase-catalyzed quinone oxidation

Mizuho Suzuki
Abstract In this study, the availability of chitosan was systematically investigated for removal of bisphenol A (BPA, 2,2-bis(hydroxyphenyl)propane) through the tyrosinase-catalyzed quinone oxidation and subsequent quinone adsorption on chitosan beads. In particular, the process parameters, such as the hydrogen peroxide (H2O2)-to-BPA ratio, pH value, temperature, and tyrosinase dose, were discussed in detail for the enzymatic quinone oxidation. Tyrosinase-catalyzed quinone oxidation of BPA was effectively enhanced by adding H2O2 and the optimum conditions for BPA at 0.3 mM were determined to be pH 7.0 and 40C in the presence of H2O2 at 0.3 mM ([H2O2]/[BPA] = 1.0). Removal of BPA from aqueous solutions was accomplished by adsorption of enzymatically generated quinone derivatives on chitosan beads. The use of chitosan in the form of beads was found to be more effective because heterogeneous removal of BPA with chitosan beads was much faster than homogeneous removal of BPA with chitosan solutions, and the removal efficiency was enhanced by increasing the amount of chitosan beads dispersed in the BPA solutions and BPA was completely removed by quinone adsorption in the presence of chitosan beads more than 0.10 cm3/cm3. In addition, a variety of bisphenol derivatives were completely or effectively removed by the procedure constructed in this study, although the enzyme dose or the amount of chitosan beads was further increased as necessary for some of the bisphenol derivatives used. 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

Two cinnamate derivatives produce similar alteration in mRNA expression and activity of antioxidant enzymes in rats

Mi-Kyung Lee
Abstract Cinnamate is a widespread secondary metabolite of phenolic compound synthesized by plants for defensive purposes. The current study was designed to investigate the effect of two structurally related cinnamate derivatives, 4-hydroxycinnamate and 3-(4-hydroxyphenyl)propionic acid (HPP), on the mRNA expression and activity of antioxidant enzymes in high-cholesterol-fed rats. Male rats were fed a 1 g/100 g high-cholesterol diet with supplements of either 4-hydroxycinnamate or HPP (0.135 mmol/100 g diet) for 6 weeks. The plasma paraoxonase activity was found to be higher in the cinnamate-derivative-supplemented groups than in the control group. The erythrocyte superoxide dismutase (SOD) and catalase (CAT) activities, plus glutathione (GSH) level, were all significantly higher in the 4-hydroxycinnamate- and HPP-supplemented groups than in the control group. However, both 4-hydroxycinnamate and HPP supplementation significantly lowered the hepatic activities and mRNA expression of CAT and glutathione peroxidase (GSH-Px) compared to the control group. The hepatic mRNA expression and activity of SOD did not differ between the groups. The hepatic thiobarbituric acid reactive substances (TBARS) level was significantly lowered by the 4-hydroxycinnamate and HPP supplementation. Accordingly, these results indicate that supplementation by 4-hydroxycinnamate and HPP would seem to enhance the antioxidative defense of erythrocyte. Both HPP and 4-hydroxycinnamate would appear to be beneficial in improving the function of antioxidative enzymes on a molecular level in high-cholesterol-fed rats. 2003 Wiley Periodicals, Inc. J Biochem Mol Toxicol 17:255,262, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.10087 [source]

Bond-based 3D-chiral linear indices: Theory and QSAR applications to central chirality codification

Juan A. Castillo-Garit
Abstract The recently introduced non-stochastic and stochastic bond-based linear indices are been generalized to codify chemical structure information for chiral drugs, making use of a trigonometric 3D-chirality correction factor. These improved modified descriptors are applied to several well-known data sets to validate each one of them. Particularly, Cramer's steroid data set has become a benchmark for the assessment of novel quantitative structure activity relationship methods. This data set has been used by several researchers using 3D-QSAR approaches such as Comparative Molecular Field Analysis, Molecular Quantum Similarity Measures, Comparative Molecular Moment Analysis, E-state, Mapping Property Distributions of Molecular Surfaces, and so on. For that reason, it is selected by us for the sake of comparability. In addition, to evaluate the effectiveness of this novel approach in drug design we model the angiotensin-converting enzyme inhibitory activity of perindoprilate's ,-stereoisomers combinatorial library, as well as codify information related to a pharmacological property highly dependent on the molecular symmetry of a set of seven pairs of chiral N -alkylated 3-(3-hydroxyphenyl)-piperidines that bind ,-receptors. The validation of this method is achieved by comparison with earlier publications applied to the same data sets. The non-stochastic and stochastic bond-based 3D-chiral linear indices appear to provide a very interesting alternative to other more common 3D-QSAR descriptors. 2008 Wiley Periodicals, Inc. J Comput Chem, 2008 [source]

Synthesis of some pyrazolo[1,5- c][1,3]benzoxazines and a new 5H -pyrazolo[1,5-c][1,3,2]benzoxazaphosphorine ring system

Jan Svetlik
Condensations of 5-(2-hydroxyphenyl)pyrazoline 3a with 4-carboxybenzaldehyde, glyoxylic acid and N,N -carbonyldiimidazole leading to pyrazolobenzoxazine derivatives were studied. The observed diastere-oselectivity is discussed. Reaction of 3a with Lawesson reagent gave rise to a new 5H -pyrazolo[1,5-c]-[1,3,2]benzoxazaphosphorine heterocyclic system. [source]

Total synthesis of homalicine and its related dihydro aglycon

Khosrow Zamani
The condensation of homophthalic acid (1) with 3-methoxybenzoyl chloride, followed by demethylation gave 3-(3-hydroxyphenyl)isocoumarin (3b). Reaction of (3b) with ,-tetraacetobromo glucose yielded tetraacetylhomalicine (3d), which was deacetylated to homalicine (3e). [source]

The effect of temperature on the stability of compounds used as UV-MALDI-MS matrix: 2,5-dihydroxybenzoic acid, 2,4,6-trihydroxyacetophenone, ,-cyano-4-hydroxycinnamic acid, 3,5-dimethoxy-4-hydroxycinnamic acid, nor-harmane and harmane

Olga I. Tarzi
Abstract The thermal stability of several commonly used crystalline matrix-assisted ultraviolet laser desorption/ionization mass spectrometry (UV-MALDI-MS) matrices, 2,5-dihydroxybenzoic acid (gentisic acid; GA), 2,4,6-trihydroxyacetophenone (THA), ,-cyano-4-hydroxycinnamic acid (CHC), 3,5-dimethoxy-4-hydroxycinnamic acid (sinapinic acid; SA), 9H-pirido[3,4-b]indole (nor-harmane; nor-Ho), 1-methyl-9H-pirido[3,4-b]indole (harmane; Ho), perchlorate of nor-harmanonium ([nor-Ho + H]+) and perchlorate of harmanonium ([Ho + H]+) was studied by heating them at their melting point and characterizing the remaining material by using different MS techniques [electron ionization mass spectrometry (EI-MS), ultraviolet laserdesorption/ionization-time-of-flight-mass spectrometry (UV-LDI-TOF-MS) and electrospray ionization-time-of-flight-mass spectrometry (ESI-TOF-MS)] as well as by thin layer chromatography analysis (TLC), electronic spectroscopy (UV-absorption, fluorescence emission and excitation spectrosco y) and 1H nuclear magnetic resonance spectroscopy (1H-NMR). In general, all compounds, except for CHC and SA, remained unchanged after fusion. CHC showed loss of CO2, yielding the trans-/cis -4-hydroxyphenylacrilonitrile mixture. This mixture was unambiguously characterized by MS and 1H-NMR spectroscopy, and its sublimation capability was demonstrated. These results explain the well-known cluster formation, fading (vanishing) and further recovering of CHC when used as a matrix in UV-MALDI-MS. Commercial SA (SA 98%; trans -SA/cis -SA 5 : 1) showed mainly cis- to- trans thermal isomerization and, with very poor yield, loss of CO2, yielding (3,,5,-dimethoxy-4,-hydroxyphenyl)-1-ethene as the decarboxilated product. These thermal conversions would not drastically affect its behavior as a UV-MALDI matrix as happens in the case of CHC. Complementary studies of the photochemical stability of these matrices in solid state were also conducted. Copyright 2008 John Wiley & Sons, Ltd. [source]

MALDI-TOF mass spectrometric analysis for the characterization of the 5,10,15,20-tetrakis- (m -hydroxyphenyl)bacteriochlorin (m -THPBC) photoproducts in biological environment

Henri-Pierre Lassalle
Abstract Photoproducts formation upon irradiation (739 nm) of 5,10,15,20-tetrakis(m -hydroxyphenyl)bacteriochlorin (m -THPBC) in phosphate buffer saline (PBS) supplemented with human serum albumin (HSA) were studied by means of absorption spectroscopy and MALDI-TOF mass spectrometry. The experiments were performed with a freshly prepared PBS,HSA solution of m -THPBC and with a PBS,HSA m -THPBC solution incubated for 6 h at 37 C. The incubation of m -THPBC solution leads to the dye monomerisation, whereas in the freshly prepared solution, m -THPBC is under an aggregated form. Regardless of the incubation condition, photobleaching experiments carried out by absorption spectroscopy demonstrate the degradation of the photosensitizer and its phototransformation in m -THPC. Moreover, m -THPC was the sole photoproduct detected using absorption spectroscopy. Together with a degradation of m -THPBC and formation of m -THPC, MALDI-TOF mass spectrometry evidenced several other photoinduced modifications. Photoproducts such as dihydroxy m -THPBC and dihydroxy m -THPC were detected in both conditions; however, the formation of hydroxylated photoproducts was significantly greater in incubated solution. In addition, small molecules arising from the degradation of the photosensitizer and identified as dipyrin derivatives and dipyrrolic synthon were observed. Copyright 2005 John Wiley & Sons, Ltd. [source]

Characterization by matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry of the major photoproducts of temoporfin (m -THPC) and bacteriochlorin (m -THPBC)

Marc Angotti
Abstract The photobleaching of 5,10,15,20-tetrakis(m -hydroxyphenyl)chlorin (temoporfin, m -THPC) and 5,10,15,20-tetrakis(m -hydroxyphenyl)bacteriochlorin (bacteriochlorin, m -THPBC) was studied in ethanol,water (1 : 99, v/v) and in physiological medium (phosphate-buffered saline, PBS) with or without fetal calf serum (FCS). m -THPC solution was irradiated with the laser radiation of 650 nm, whereas m -THPBC solution underwent two consecutive irradiations at 532 and 650 nm. The photoproducts were characterized by UV,visible absorption spectrophotometry and by matrix-assisted laser desorption/ionization (MALDI) coupled with Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS). Independent of the solvent used, the phototransformation of either photosensitizer yielded the formation of 5,10,15,20-tetrakis (m -hydroxyphenyl)porphyrin (m -THPP) through a major dehydrogenation process. Copyright 2001 John Wiley & Sons, Ltd. [source]

Signaling pathways of bisphenol A,induced apoptosis in hippocampal neuronal cells: Role of calcium-induced reactive oxygen species, mitogen-activated protein kinases, and nuclear factor,,B

Soyoung Lee
Abstract In the present study, we investigated the neurotoxicity of bisphenol A [BPA; 2,2-bis-(4 hydroxyphenyl) propane] and the underlying mechanisms of action in mouse hippocampal HT-22 cells. BPA, known to be a xenoestrogen, is used in the production of water bottles, cans, and teeth suture materials. BPA-treated HT-22 cells showed lower cell viability than did controls at concentrations of BPA over 100 ,M. BPA induced apoptotic cell death as indicated by staining with Hoechst 33258, costaining with Annexin V/propidium iodide, and activation of caspase 3. BPA regulated the generation of reactive oxygen species (ROS) by increasing intracellular calcium. BPA activated phosphorylation of extracellular signal,regulated kinase (ERK) and c-Jun N-terminal kinase (JNK), and nuclear translocation of nuclear factor (NF)-,B. Pretreatment with specific inhibitors for calcium, ROS, ERK, and JNK decreased BPA-induced cell death; however, inhibitor for NF-,B increased BPA-induced cell death. The results suggest that calcium, ROS, ERK, and JNK are involved in BPA-induced apoptotic cell death in HT-22 cells. In contrast, an NF-,B cascade was activated for survival signaling after BPA treatment. 2008 Wiley-Liss, Inc. [source]

Primary kinetic hydrogen isotope effects in deprotonations of a nitroalkane by intramolecular phenolate groups

Nicholas Backstrom
Abstract Rate constants and kinetic isotope effects have been determined for the formation of nitronate anions from the ethers 1-(2-methoxyphenyl)-2-nitropropane, 7(X,=,H, L,=,H and D) and 1-(2-methoxy-5-nitrophenyl)-2-nitropropane, 7(X,=,NO2, L,=,H and D), and from the corresponding phenols, 1-(2-hydroxyphenyl)-2-nitropropane, 3(X,=,H, L,=,H and D), and 1-(2-hydroxy-5-nitrophenyl)-2-nitropropane, 3(X,=,NO2, L,=,H and D), in aqueous basic medium. For the ethers 7, rates of deprotonation by hydroxide are comparable with those found for deprotonations of 2-nitropropane, with kH/kD (25,C),=,7.7 and 7.8, respectively. In both the cases, the isotope effects are conventionally temperature dependent. For the corresponding phenols 3, conditions have been established under which the deprotonations of the nitroalkane are dominated by intramolecular deprotonation by the kinetically first-formed phenolate anion, with an estimated effective molarity EM,,,250. For 3 (X,=,H, L,=,H or D), kH/kD (25,C),=,7.8, with E,,,E,=,6.9,kJ,mol,1 and AH/AD,=,0.5. For 3(X,=,NO2, L,=,H or D), rates of intramolecular deprotonation are reduced 30-fold, and an elevated kinetic isotope effect is found (kH/kD (25,C),=,10.7). Activation parameters (E,,,E,=,17.8,kJ,mol,1 and AH/AD,=,0.008) are compatible with an enhanced tunnelling contribution to reactivity in the H-isotopomer. Copyright 2009 John Wiley & Sons, Ltd. [source]

Synthesis and polymerization reactions of cyclic imino ethers.


Abstract Homopolyaddition reactions of AB-type monomers containing a 2-oxazoline and a phenol group in different positions of the phenyl ring, namely, 2-(4-hydroxyphenyl)-2-oxazoline, 2-(3-hydroxyphenyl)-2-oxazoline, 2-(2-hydroxyphenyl)-2-oxazoline, and 2-(4-hydroxyphenyl)-4,4-dimethyl-2-oxazoline, were studied. Except for 2-(4-hydroxyphenyl)-4,4-dimethyl-2-oxazoline, the reaction carried out in bulk or a solution of highly boiling solvents resulted in the formation of poly(ether amide)s with molecular weights in the range of 103 to 104 as measured by vapor pressure osmometry and gel permeation chromatography. A mechanism of the growth reaction, including a nucleophilic attack of a phenol group to a 2-oxazoline ring in the 5-position, was suggested. The polymerization was accompanied by a side reaction of the amido groups formed by the primary reaction of the 2-oxazoline ring. This led to branching of the main chain. The thermal properties of the prepared polymers were evaluated. 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 343,355, 2006 [source]

Synthesis, characterization, and in vitro degradation of liquid-crystalline terpolyesters of 4-hydroxyphenylacetic acid/3-(4-hydroxyphenyl)propionic acid with terephthalic acid and 2,6-naphthalene diol

V. S. Prasad
Abstract Melt-processable liquid-crystalline terpolyesters of 4-hydroxyphenylacetic acid (HPAA) and 3-(4-hydroxyphenyl)propionic acid (HPPA) with terephthalic acid and 2,6-naphthalene diol were synthesized by one-step acidolysis melt polycondensation followed by postpolymerization and were characterized with viscosity studies, Fourier transform infrared (FTIR) and NMR spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), polarized light microscopy, and wide-angle X-ray diffraction. The melting behaviors and liquid-crystalline transition temperatures of the terpolyesters were dependent on the composition of the HPAA/HPPA content. The transition temperatures of the polyesters could be effectively reduced by the introduction of an even number of built-in short methylene spacers in combination with the 2,6-naphthalene offset structure. A terpolyester with an HPPA content of 33% (NTP33) showed optimum properties for the glass-transition temperature, around 71 C, and the melting temperature, near 240 C, with a Schlieren nematic texture. The polymer showed excellent flow behavior in a Brabender plasticorder. It was also thermally stable up to 400 C. NTP33 showed 2.5% in vitro hydrolytic degradation in buffer solutions of pH 10 at 60 C after 540 h. Considerable enzymatic degradation was also observed with porcine pancreas lipase/buffer solutions in comparison with Candida rugosa lipase after 60 days. The degradation was also followed with FTIR, DSC, and TGA. Apart from the temperature and pH of the buffer solution, several structural parameters, such as the aromatic content, crystallinity percentage, and composition of the polymer, affected the degradation behavior. FTIR studies indicated the involvement of chain scission during degradation. Scanning electron microscopy studies further showed that surface erosion also played a major role in the degradation. 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1845,1857, 2002 [source]

Synthesis, characterization, and in vitro degradation of thermotropic polyesters and copolyesters based on terephthalic acid, 3-(4-hydroxyphenyl)propionic acid, and glycols

Minoru Nagata
Abstract A new series of thermotropic liquid-crystalline (LC) polyesters were prepared from a diacyl chloride derivative of 4,4,-(terephthaloyldioxy)-di-4-phenylpropionic acid (PTP) and glycols with a different number of methylene groups (n) [HO(CH2)n OH, n = 6,10, 12] by high-temperature solution polycondensation in diphenyl oxide. PTP6/10 and PTP6/hydroquinone (H) LC copolyesters were also prepared according to a similar procedure. The chemical structure, LC, phase-transition behaviors, thermal stability, and solubility were characterized by elemental analysis, Fourier transform infrared spectroscopy, 1H and 13C NMR spectra, differential scanning calorimetry (DSC), thermogravimetric analysis, and a polarizing light microscope. The melting and isotropization temperatures decreased in a zigzag manner as the number of n increased. All of the polyesters formed a nematic phase with the exception of PTP8. The temperature ranges of the mesophase (,T) were much wider for the polyesters with an odd number of n's than those with an even number. ,T increased markedly for the PTP6/10 and PTP6/H copolyesters. The in vitro degradations of the polymers were ascertained by enzymatic hydrolysis and alkaline hydrolysis. The model compound, PTP dihexylester, was synthesized and found to be degraded into terephthalic acid, 3-(4-hydroxyphenyl)propionic acid, and 1-hexanol by Rhizopus delemar lipase, but PTPn homopolyesters and PTP6/10 and PTP6/H copolyesters were resistant to Rhizopus delemar hydrolysis. They were degradable in a sodium hydroxide buffer solution of pH 12 at 60 C, depending on the number of n's and the copolymer composition. 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3043,3051, 2001 [source]

Properties and Bioapplications of Blended Cellulose and Corn Protein Films

Quanling Yang
Abstract A series of blend films have been prepared from cellulose and corn protein in a NaOH/urea solution by a simple, low cost, and ,green' pathway. Their structure and properties are characterized by amino acid analysis, X-ray diffraction, scanning electron microscopy, thermogravimetry, and tensile testing. The results reveal that a certain miscibility exists between cellulose and corn protein and their thermal stability and mechanical properties are improved significantly, compared with the protein materials, when the protein content is less than 18 wt.-%. The protein, which contains tyrosine and histidine, could remain in the blend films after being washed for ten days, which indicates the strong hydrogen bonding between the hydroxy groups of cellulose and the hydroxyphenyl of tyrosine and imidazolyl of histidine in the protein. Furthermore, they exhibit good biocompatibility capable of supporting cell adhesion and proliferation. [source]

Corrosion control of phenylthiourea polymers on aluminium in alkaline medium

B. J. Vasanthi
Simple phenylthiourea compounds are known for their high solubility in alkaline medium and for good corrosion control. The monomer N -(4-hydroxy-3-methoxybenzal)- N,-(4,-hydroxyphenyl) thiourea was condensed with pimeloylchloride and azeloylchloride through inter-facial polycondensation method to synthesize the polymers. The polymers were dissolved in 2 N sodium hydroxide and their corrosion controlling efficiency on aluminium was studied through AC impedance and potentiodynamic polarization methods. [source]

Evaluation of the environmental fate of thymol and phenethyl propionate in the laboratory

Dingfei Hu
Abstract BACKGROUND: The natural monoterpenoid pesticides thymol and phenethyl propionate (PEP) are used indoors and outdoors, but their fate in the environment has not been reported. In order better to understand their impact on the environment, water metabolism and soil metabolism studies were conducted with thymol and PEP at a concentration of 10 g g,1 in water and in soil under laboratory conditions. RESULTS: Dissipation half-lives of thymol and PEP were 16 and 5 days in water and 5 and 4 days in soil. 2-Phenylethanol and 2-(4-hydroxyphenyl)ethanol were detected as primary degradation products of PEP. Over time, a considerable volatilization loss of thymol, but not of phenethyl propionate, was found in the 1 month study under the experimental conditions used. Less than 6% of thymol and PEP were detected as bound residues, and less than 3% were mineralized during the 30 day study. CONCLUSION: In order to maximize the pesticidal effect, more attention should be paid to the temperature for thymol than for PEP when they are being applied, owing to the high volatility of the former. Thymol and PEP pose low risks to the ecosystem because of their rapid dissipation and low bound residues in the environment. Copyright 2008 Society of Chemical Industry [source]