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Compound I (compound + i)

Distribution by Scientific Domains

Chemistry	83%

Distribution within Chemistry

Biochemistry	30%

Selected Abstracts

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

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 6 2006
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) Å, b = 16.899(6) Å, c = 17.872(5) Å, , = 65.957(7)°, , = 83.603(5)°, , ( = 75.242(5)°, V = 2549.8(13) Å3, 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) Å, b = 5.9270(9) Å, c = 27.975(4) Å; , = 90°, , = 95.081(3)°, , = 90°, V = 1262.7(3) Å3, 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]

Theory of chemical bonds in metalloenzymes XIII: Singlet and triplet diradical mechanisms of hydroxylations with iron-oxo species and P450 are revisited

INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 15 2009
Kizashi Yamaguchi
Abstract Electronic structures of the Compound I (CpdI) in P450 are investigated on the basis of spin coupling forms of iron-oxo (Fe(IV)O) cores and radical ligand (,L) groups to generalize previous singlet and triplet diradical (TD) mechanisms for oxygenations of alkanes with Fe( IV)O. Orbital interaction schemes for four lower-lying spin configurations of CpdI with HC bond of substrate are examined to elucidate how magnetic coupling modes correlate with radical reaction pathways for hydroxylation reactions on the basis of the broken symmetry (BS) molecular orbital (MO) model. The configuration correlation diagrams for the four configurations model are depicted on the basis of the isoelectronic analogy among O, O2, and Fe( IV)O, in addition to Coulomb exchange energy on the iron site, which determines its local spin configuration. Important role of ligand spin (,L) of CpdI for regulation of hydroxylation mechanisms is clarified with the aid of the spin coupling forms. Transition states for one quartet and three doublet configurations under the BS MO approximation are examined on the basis of potential curve crossings along reaction pathways. The four transition structures and corresponding radical intermediates for methane and trimethyl methane with CpI are located by the BS hybrid Kohn,Sham density functional theory (DFT) (B3LYP) method to confirm the orbital interaction schemes. Spin density populations obtained by the BS B3LYP calculations are found to be consistent with the theoretical predictions based on the four configurations model. The configuration and state correlation diagrams by BS B3LYP before and after spin projection are also consistent with the BS MO interaction schemes, which provide local SD and TD mechanisms of hydroxylation with CpdI. The present BS MO-theoretical framework is useful for systematic understanding of a lot of recent BS hybrid DFT computational results for hydroxylation reactions with CpdI and configuration correlation diagrams reported by several groups. Implications of the present theoretical and computational results are discussed in relation to several experimental characteristics of hydroxylation reactions with iron-oxo species and P450. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009 [source]

Inorganic,Organic Hybrid Structures: Open-Framework Iron Phosphite,Oxalates of Varying Dimensionality

CHEMISTRY - A EUROPEAN JOURNAL, Issue 3 2007
Sukhendu Mandal
Abstract Inorganic,organic hybrid structures belonging to the family of iron phosphite,oxalates have been prepared by employing hydrothermal methods. Their structures, determined by single-crystal X-ray diffraction, show a hierarchy within the family. While compounds I and II are low dimensional, III,VI have three-dimensional structures. Compound I has edge-shared ladders of iron phosphite with oxalate units hanging from the iron centers. Compound II has a layer structure with a honeycomb-like arrangement. The three-dimensional hybrid structures have the oxalate units connected in both in-plane and out-of-plane modes. A newly identified secondary building unit (SBU-7) and the oxalate units satisfying the valence and coordination requirements in the structure of V are novel and noteworthy structural features. Magnetic studies show that the dominant interactions between the iron centers are antiferromagnetic. Similar to other known hybrid structures, the phosphite,oxalate structures appear to show wide compositional and structural diversity. [source]

Crystal Structure, Solid-State NMR Spectroscopic and Photoluminescence Studies of Organic-Inorganic Hybrid Materials (HL)6[Ge6(OH)6(hedp)6]·2(L)·nH2O, L = hqn or phen,

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 23 2006
Luís Mafra
Abstract Two germanium,hedp4, solids with heteroaromatic amines 8-hydroxyquinoline (hqn) and 1,10-phenanthroline (phen), (HL)6[Ge6(OH)6(hedp)6]·2(L)·nH2O (L = hqn or phen), in I and II respectively, have been prepared and characterised by single-crystal XRD, thermogravimetry, FTIR and UV/Vis spectroscopy. The complex hydrogen-bond networks, particularly in compound I, have been studied by advanced high-resolution solid-state NMR spectroscopy that combines homonuclear recoupling techniques (two-dimensional 1H- 1H DQF and 1H- 1H RFDR MAS NMR) and combined rotation and multiple-pulse spectroscopy (two-dimensional 1H- 1H FS-LG, 1H- 31P FS-LG). The fine details of the crystal structure of I have been elucidated, mainly those involving the ,,, stacking of 8-hydroxyquinoline and the relative orientation of adjacent such molecules. Compound II exhibits an emission from the lowest triplet-state energy (,,,* 0-phonon transition) of the aromatic rings at 320 nm (31250 cm,1) from 14 K to room temperature. In contrast, the triplet emission of I at 530 nm (18868 cm,1) is only detected at low temperature, because of thermally activated non-radiative mechanisms. The emission spectra of I and II display a lower-energy component with a larger life time, which results from the formation of an excimer state that originated from the ,,, phenanthroline and hydroxyquinoline interactions, respectively. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]

Redox properties of the couple compound I/native enzyme of myeloperoxidase and eosinophil peroxidase

FEBS JOURNAL, Issue 19 2001
Jürgen Arnhold
The standard reduction potential of the redox couple compound I/native enzyme has been determined for human myeloperoxidase (MPO) and eosinophil peroxidase (EPO) at pH 7.0 and 25 °C. This was achieved by rapid mixing of peroxidases with either hydrogen peroxide or hypochlorous acid and measuring spectrophotometrically concentrations of the reacting species and products at equilibrium. By using hydrogen peroxide, the standard reduction potential at pH 7.0 and 25 °C was 1.16 ± 0.01 V for MPO and 1.10 ± 0.01 V for EPO, independently of the concentration of hydrogen peroxide and peroxidases. In the case of hypochlorous acid, standard reduction potentials were dependent on the hypochlorous acid concentration used. They ranged from 1.16 V at low hypochlorous acid to 1.09 V at higher hypochlorous acid for MPO and from 1.10 V to 1.03 V for EPO. Thus, consistent results for the standard reduction potentials of redox couple compound I/native enzyme of both peroxidases were obtained with all hydrogen peroxide and at low hypochlorous acid concentrations: possible reasons for the deviation at higher concentrations of hypochlorous acid are discussed. They include instability of hypochlorous acid, reactions of hypochlorous acid with different amino-acid side chains in peroxidases as well as the appearance of a compound I,chloride complex. [source]

Effects of cadmium on manganese peroxidase

FEBS JOURNAL, Issue 6 2000
Competitive inhibition of MnII oxidation, thermal stabilization of the enzyme
Inhibition of manganese peroxidase by cadmium was studied under steady-state and transient-state kinetic conditions. CdII is a reversible competitive inhibitor of MnII in the steady state with Ki , 10 µm. CdII also inhibits enzyme-generated MnIII,chelate-mediated oxidation of 2,6-dimethoxyphenol with Ki , 4 µm. CdII does not inhibit direct oxidation of phenols such as 2,6-dimethoxyphenol or guaiacol (2-methoxyphenol) in the absence of MnII. CdII alters the heme Soret on binding manganese peroxidase and exhibits a Kd , 8 µm, similar to Mn (Kd , 10 µm). Under transient-state conditions, CdII inhibits reduction of compound I and compound II by MnII at pH 4.5. However, CdII does not inhibit formation of compound I nor does it inhibit reduction of the enzyme intermediates by phenols in the absence of MnII. Kinetic analysis suggests that CdII binds at the MnII -binding site, preventing oxidation of MnII, but does not impair oxidation of substrates, such as phenols, which do not bind at the MnII -binding site. Finally, at pH 4.5 and 55 °C, MnII and CdII both protect manganese peroxidase from thermal denaturation more efficiently than CaII, extending the half-life of the enzyme by more than twofold. Furthermore, the combination of half MnII and half CdII nearly quadruples the enzyme half-life over either metal alone or either metal in combination with CaII. [source]

Extended Hartree,Fock theory of chemical reactions.

INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 15 2008
VIII.
Abstract We have investigated the reaction pathways for the primary hydroxylation reaction of trimethylmethane by a high-valent Fe(IV)O porphyrin ,-cation radical species known as compound I at the B3LYP/CEP-31G level. The isoelectronic analogy of the Fe(IV)O core of compound I to a molecular oxygen (O2) has been successfully used to clarify the important roles of the singlet excited state of the Fe(IV)O core in the alkane hydroxylation, which has hitherto been neglected. The reaction is initiated by the rate-determining hydrogen-atom abstraction from the substrate to give a discrete radical intermediate complex, in accordance with the conventional radical rebound mechanism. Similar to the chemistry of O2, however, one of the singlet excited states, i.e., the diradical component of the 1, state of the Fe(IV)O core intercepts the triplet ground state (the 3, state) in the region of the transition state for the hydrogen abstraction. Our findings strongly indicate that the exchange polarization or intersystem crossing for the nonradiative transition to the locally singlet state is highly important to enhance the reactivity of compound I. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 [source]

A direct injection high-throughput liquid chromatography tandem mass spectrometry method for the determination of a new orally active ,v,3 antagonist in human urine and dialysate

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 22 2003
Wei Zeng
A generic high-throughput liquid chromatography (HTLC) tandem mass spectrometry (MS/MS) assay for the determination of compound I in human urine and dialysate (hemodialysis) was developed and validated. By using the HTLC on-line extraction technique, sample pretreatment was not necessary. The sample was directly injected onto a narrow bore large particle size extraction column (50,×,1.0,mm, 60,,m) where the sample matrix was rapidly washed away using a high flow rate (5,mL/min) aqueous mobile phase while analytes were retained. The analytes were subsequently eluted from the extraction column onto an analytical column using an organic-enriched mobile phase prior to mass spectrometric detection. The analytes were then eluted from the analytical column to the mass spectrometer for the determination. The linear dynamic range was 2.0,6000,ng/mL for the urine assay and 0.1,300,ng/mL for the dialysate assay. Intraday accuracy and precision were evaluated by analyzing five replicates of calibration standards at all concentrations used to construct the standard curve. For the urine assay, the precision (RSD%, n,=,5) ranged from 1.9 to 8.0% and the accuracy ranged from 87.8 to 105.2% of nominal value. For the dialysate assay, the precision (RSD%, n,=,5) ranged from 1.1 to 10.0% and the accuracy from 94.5 to 105.2% of nominal value. In-source fragmentation of the acyl glucuronide metabolite (compound III) did not interfere with the determination of parent compound I. The developed HTLC/MS/MS methodology was specific for compound I in the presence of compound III. Column life-time is increased and sample analysis time is decreased over traditional reversed-phase methods when direct injection assays for urine and dialysate are coupled with the technology of HTLC. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Hydrothermal Syntheses, Crystal Structure and Thermal Behavior of [(CH3)2NH2]2[B5O6(OH)4]2·[HCON(CH3)2] and [NH3CH2CH2NH3]2[B14O20(OH)6]

CHINESE JOURNAL OF CHEMISTRY, Issue 11 2009
Ping Li
Abstract Two novel organic base templated nonmetal borates [(CH3)2NH2]2[B5O6(OH)4]2·[HCON(CH3)2] (?) and [NH3CH2CH2NH3]2[B14O20(OH)6] (II) have been synthesized under hydrothermal conditions, and characterized by elemental analyses, FT-IR spectroscopy, X-ray diffraction, and TG-DTA. Their crystal structures were determined from single crystal X-ray diffraction. The crystal structure of compound I is characterized by forming a 3D supramolecular structure with large channels along axes b and c through OH···O hydrogen-bonding among the [B5O6(OH)4], anions. The crystal structure of compound II is characterized by forming a 3D supramolecular structure with large channels along axis a and direction [111] through OH···O hydrogen-bonding among the [B14O20(OH)6]4, anions. The templating organic amine cations in I and II are both obtained through in situ hydrothermal reactions, and are both located in the channels of the 3D supramolecular structure, respectively. Their thermal behavior has been also investigated. [source]

Tyrosinase inhibitors isolated from the roots of Paeonia suffruticosa

INTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 2 2010
H. -Y.
J. Cosmet. Sci., 60, 347,352 (May/June 2009) Accepted for publication November 6, 2008. Synopsis The inhibition of mushroom tyrosinase by Paeonia suffruticosa root-derived materials was evaluated. Six tyrosinase inhibitors were isolated by ethanol extraction, n -hexane, ethyl acetate, n -BuOH, and water partition, silica gel column chromatography, Sephadex LH-20, Lobar PR-8, and high-performance liquid chromatography methods, and they were identified as kaempferol (I), quercetin (II), mudanpioside B (III), benzoyloxypaeoniflorin (IV), mudanpioside H (V), and pentagalloyl-,-D-glucose (VI) on the basis of spectroscopic evidence. The inhibitory activities of compounds I to VI against mushroom tyrosinase were determined with IC50 values of 0.120, 0.108, 0.368, 0.453, 0.324, and 0.063 mM, respectively. The kinetic study indicated that all purified inhibitors acted competitively for the L-dopa binding site of the enzyme, with an exception of compound VI, which acted non-competitively. [source]

Spectroscopic study on structure of horseradish peroxidase in water and dimethyl sulfoxide mixture

BIOPOLYMERS, Issue 2 2002
Yasushi Maeda
Abstract The structure of horseradish peroxidase (HRP) in phosphate buffered saline (PBS)/dimethyl sulfoxide (DMSO) mixed solvents at different compositions is investigated by IR, electronic absorption, and fluorescence spectroscopies. The fluorescence spectra and the amide I spectra of ferric HRP [HRP(Fe3+)] show that overall structural changes are relatively small up to 60% DMSO. Although the amide I band of HRP(Fe3+) shows a gradual change in the secondary structure and a decrease in the contents of , helices, its fluorescence spectra indicate that the distance between the heme and Trp173 is almost constant. In contrast, the changes in the positions of the Soret bands for resting HRP(Fe3+) and catalytic intermediates (compounds I and II) and the IR spectra at the CO stretching vibration mode of carbonyl ferrous HRP [HRP(Fe2+)-CO] show that the microenvironment in the distal heme pocket is altered, even with low DMSO contents. The large reduction of the catalytic activity of HRP even at low DMSO contents can be attributed to the structural transition in the distal heme pocket. In PBS/DMSO mixtures containing more than 70 vol % DMSO, HRP undergoes large structural changes, including a large loss of the secondary structure and a dissociation of the heme from the apoprotein. The presence of the components of the amide I band that can be assigned to strongly hydrogen bonding amide CO groups at 1616 and 1684 cm,1 suggests that the denatured HRP may aggregate through strong hydrogen bonds. © 2002 John Wiley & Sons, Inc. Biopolymers (Biospectroscopy) 67: 107,112, 2002 [source]