An Efficient and Economical Method for the Preparation of Fmoc-Argω,ω'(Boc)2-OH

The arginine derivative Fmoc‐Arg^ω,ω′(Boc)₂‐OH has been prepared in perfect yield starting from Fmoc‐Orn·HCl and N,N′‐di‐Boc‐N′′‐triflyguanidine with the presence of diisopropylethylamine (DIEA). This work provides an efficient and economical method for the preparation of this compound.     

Synthesis and characterization of poly(styrene/α-t-butoxy-ω-vinylbenzyl-polyglycidol) microspheres

Polystyrene microspheres with polyglycidol (polyGL) in a surface layer were synthesized in batch radical emulsifier-free emulsion copolymerizations of styrene and surfmers, α-t-butoxy-ω-vinylbenzyl-polyGL macromonomers (VB-polyGL). Macromonomers with number-average molecular weight Mˉ _n=950 (VB-polyGL950) and Mˉ _n=2700 (VB-polyGL2700) were used for these polymerizations. In all syntheses the initial concentrations of styrene and initiator (K₂S₂O₈) were constant. The initial macromonomer-to-styrene ratios were varied from 1.10 × 10⁻³ to 1.64 × 10⁻² mol/mol and from 3.46 × 10⁻⁴ to 3.47 × 10⁻³ mol/mol for VB-polyGL950 and VB-polyGL2700, respectively. The diameters of microspheres obtained were smaller for the syntheses with higher concentrations of macromonomers. Syntheses with VB-polyGL950 yielded microspheres with number-average diameters (Dˉ _n) from 216 to 900 nm and with a bimodal diameter distribution. The number-average diameters of microspheres obtained with VB-polyGL2700 varied from 220 to 650 nm, depending on the initial concentration of macromonomer. Their diameter distributions were monomodal, with a diameter polydispersity parameter (ratio of weight-average and number-average diameters) in the range 1.007≤Dˉ _w/Dˉ _n≤1.022. For each type of microsphere the fraction of polyGL in a surface layer and the surface concentration of sulfate anions were determined. The fraction of polyGL in the surface layer was related to the initial monomer composition in the polymerizing mixture. Adsorption of human serum albumin onto surfaces of some poly(styrene/VB-polyGL) microspheres was up to 10 times lower than for the polystyrene microspheres obtained in a similar emulsifier-free emulsion polymerization of styrene. Received: 26 September 2000/Accepted: 19 February 2001     

N,N′-dipyridoxyl(ethylenediamine) schiff-base ligand and its square-pyramidal copper(II) complex: Synthesis, experimental and theoretical characterization

A new tetradentate N,N??-dipyridoxyl(1,2-ethylenediamine) [=H₂ES] Schiff-base ligand and its Cu(II) salen complex [Cu(ES)(H₂O)] are synthesized and characterized by IR, UV-Vis, ¹H NMR, mass spectrometry, and elemental analysis. Their optimized geometries and theoretical vibrational frequencies are computed by using the density functional theory method where the B3LYP functional was used. Also, the ¹H NMR chemical shifts of the H₂ES ligand are calculated at the same computational level. In the optimized structure of the free ligand, two pyridine rings are not in the same plane. In the structure of the complex, the Schiff-base ligand acts as a dianionic tetradentate ligand in the N, N, O^?, O^? manner, so that the coordinating atoms occupy equatorial positions. The H₂O ligand occupies the axial position of the squarepyramidal complex. The calculated results are consistent with the experimental ones, confirming the suitability of the optimized structures for the H₂ES ligand and its Cu(II) complex.     

Synthesis,characterization and nucleolytic property of bis(N,N′-dimethylglycinato)copper(II)

Aquabis(N,N-dimethylglycinato)copper(II) dihydrate, [Cu(dmg)₂(H₂O)]·2H₂O, has been synthesized and characterized by elemental analysis, FT-IR, magnetic data, thermal analysis, solution UV-visible spectroscopy, X-ray crystal structure analysis and electrospray ionization mass spectroscopy. The square pyramidal copper(II) complex crystallizes in the orthorhombic space group P2₁2₁2₁. The complex cleaves circular plasmid DNA (pBR322) in the presence of H₂O₂. The extent of cleavage varies with the concentration range of the complex, the type of buffer used, pH of buffer and the concentration of H₂O₂. Hydroxyl radical scavenger can inhibit the nucleolytic ability of this complex.     

Synthesis and characterization of N,N,N′,N′-tetraalkyl-4-oxaheptanediamide as extractant for extraction of uranium(VI) and thorium(IV) ions from nitric acid solution

Tridentate ligand N,N,N′,N′-tetraoctyl-4-oxaheptanediamide(TOOHA) and other three analogous diamides have been prepared and characterized by using NMR spectra and element analysis. The extraction of UO₂ ²⁺ and Th⁴⁺ with the present extractants was investigated at 293 ± 1 K from nitric acid solutions. n-Octane was found to be the most suitable diluent in the present study compared with other diluents tested. Extraction distribution ratios (D) of U(VI) and Th(IV) have been studied as a function of aqueous concentrations of HNO₃, extractant concentrations. The results indicated that U(VI) is mainly extracted as UO₂(NO₃)₂·2TOOHA. In the case of Th⁴⁺ ion, the possible compositions of extracted species in organic phase were presumed to be Th(NO₃)₄·2TOOHA and Th(NO₃)₄·3TOOHA. In addition, the influence of concentration of sodium nitrate as salting-out agent on the distribution ratio of U(VI) and Th(IV) with TOOHA was also evaluated.     

Facile synthesis and characterization of phosphorescent Pt(N(∧)C(∧)N)X complexes

In order to investigate the ground state and excited state properties of Pt(N(∧)C(∧)N)X, we have prepared a series of Pt complexes, where N(∧)C(∧)N aromatic chelates are derivatives of m-di(2-pyridinyl)benzene (dpb) and X are monoanionic and monodentate ancillary ligands including halide and phenoxide. Facile synthesis of platinum m-di(2-pyridinyl)benzene chloride and its derivatives, using controlled microwave heating, was reported. This method not only shortened the reaction time but also improved the reaction yield for most of the Pt complexes. Two Pt(N(∧)C(∧)N)X complexes have been structurally characterized by X-ray crystallography. The change of functional group does not affect the structure of the core Pt(N(∧)C(∧)N)Cl fragment. Both molecules pack as head-to-tail dimers, each molecule of the dimer related to the other by a center of inversion. The electrochemical studies of all Pt complexes demonstrate that the oxidation process occurs on the metal-phenyl fragment and the reduction process is associated with the electron accepting groups like pyridinyl groups and their derivatives. The maximum emission wavelength of the Pt(N(∧)C(∧)N)X complexes ranges between 471 and 610 nm, crossing the spectrum of visible light. Most of the Pt complexes are strongly luminescent (Φ = 0.32-0.63) and have short luminescence lifetimes (τ = 4-7 μs) at room temperature. The lowest excited state of the Pt(N(∧)C(∧)N)X complexes is identified as a dominant ligand-centered (3)π-π* state with some (1)MLCT/(3)MLCT character, which appears to have a larger (1)MLCT component than their bidentate and tridentate analogs. This results in a high radiative decay rate and high quantum yield for Pt(dpb)Cl and its analogs. However, the excited state properties of the Pt(N(∧)C(∧)N)X complexes are strongly dependent on the nature of the electron-accepting groups and substituents to the metal-phenyl fragment. A rational design will be needed to tune the emission energies of the Pt(N(∧)C(∧)N)X complexes over a wide range while maintaining their high luminescent efficiency.     

α-(3-Pyridyl)malonates: preparation and synthetic applications

Alkylation of aromatic rings is a major challenge in organic syntheses since more complex carbon skeletons can be constructed. The alkylation of pyridine by nucleophilic aromatic substitution of the nitro group in methyl 3-nitro-4-pyridylcarboxylate (1) with malonic ester is reported. The versatility of the α-(3-pyridyl) malonic ester product (3) is demonstrated by the formation of a number of new 3-alkylated pyridines and new fused bis-heterocycles. cis 2-Halomethyl-4-(3-pyridyl)tetrahydrofuran products were selectively prepared. Exact ¹H and ¹³C NMR assignments of practically all products were obtained by a series of NMR experiments.     

Synthesis and characterization of monomeric and dimeric palladium(II)–ammonium complexes: their use for the catalytic oxidation of alcohols

The addition of quaternary ammonium salts, R₄NX, to PdCl₂ leads to mononuclear anionic complexes: (R₄N)₂PdX₄. A dinuclear complex, (n-Bu₄N)₂Pd₂Cl₆, has been characterized from the crystallization of the corresponding monomeric species under controlled conditions. These complexes revealed a similar efficiency as mixtures of PdCl₂ and R₄NX for the catalytic oxidation of alcohols using 1,2-dichloroethane as both solvent and stoichiometric oxidant.     

Mononuclear copper(I) complexes with triphenylphosphine and N,N′-disubstituted thioureas: synthesis,characterization, and biological evaluation

Abstract

Twelve new complexes, of the general formula CuCl(TPP)₂Tu^1–12 (Tu?=?thiourea), were synthesized by the reaction of CuCl(TPP)₃ (TPP?=?triphenylphosphine) and various N,N′-disubstituted thioureas. The structures of the synthesized complexes were characterized by different techniques such as Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy (¹H, ¹³C, ³¹P, and ¹⁹F), and the representative complexes (1, 2 and 12) were analyzed via single crystal X-ray diffraction. The single crystal X-ray analysis revealed that copper(I) is coordinated with chlorine, two TPP, and the thiourea ligands through the sulfur atom in a mononuclear distorted tetrahedral mode. The compounds were tested for antibacterial, antifungal, cytotoxicity, antileishmanial, and antioxidant activities. The results showed that the synthesized complexes are significantly more active than the free ligands and the commercial reference compounds. The high biological activities of the complexes versus free ligands can be attributed to the copper(I) chloride complexation with thiourea ligands. The synthesized complexes were also evaluated, both experimentally and theoretically, for DNA binding studies. The UV-visible spectroscopic and molecular docking studies demonstrated that the complexes are conjugating with DNA through a groove binding mode.     

Advances and trends in the design, analysis, and characterization of polymer–protein conjugates for “PEGylaided” bioprocesses

In addition to their use as therapeutics and because of their enhanced properties, PEGylated proteins have potential application in fields such as bioprocessing. However, the use of PEGylated conjugates to improve the performance of bioprocess has not been widely explored. This limited additional industrial use of PEG-protein conjugates can be attributed to the fact that PEGylation reactions, separation of the products, and final characterization of the structure and activity of the resulting species are not trivial tasks. The development of bioprocessing operations based on PEGylated proteins relies heavily in the use of analytical tools that must sometimes be adapted from the strategies used in pharmaceutical conjugate development. For instance, to evaluate conjugate performance in bioprocessing operations, both chromatographic and non-chromatographic steps must be used to separate and quantify the resulting reaction species. Characterization of the conjugates by mass spectrometry, circular dichroism, and specific activity assays, among other adapted techniques, is then required to evaluate the feasibility of using the conjugates in any operation. Correct selection of the technical and analytical methods in each of the steps from design of the PEGylation reaction to its final engineering application will ensure success in implementing a "PEGylaided" process. In this context, the objective of this review is to describe technological and analytical trends in developing successful applications of PEGylated conjugates in bioprocesses and to describe potential fields in which these proteins can be exploited.     

Graphene oxide anchored with sulfonic acid-functionalized glycerin: production,characterization and catalytic performance for the synthesis of N,N′-alkylidene bisamides

Research on Chemical Intermediates - A novel nanosheet-structured material, namely graphene oxide anchored with sulfonic acid-functionalized glycerin (GO@Gl-SO3H), was prepared and characterized by...     

Co(III) N,N′-diarylformamidine dithiocarbamate complexes: Synthesis,characterization, crystal structures and biological studies

Three symmetric N,N-diarylformamidine dithiocarbamates, N,N′-bis(2,6-dimethylphenyl)formamidine dithiocarbamate (DTL1), N,N′-bis(2,6-disopropylphenyl)formamidine dithiocarbamate (DTL2) and N,N′-dimesitylformamidine dithiocarbamate (DTL3), and three unsymmetric ones, N′-(2,6-dichlorophenyl-N-(2,6-dimethylphenyl)formamidine dithiocarbamate (DTL4), N′-(2,6-dichlorophenyl)-N-(2,6-diisopropylphenyl)formamidine dithiocarbamate (DTL5) and N′-(2,6-dichlorophenyl)-N-mesitylformamidine dithiocarbamate (DLT6), were reacted with chloridocobalt(III) in water to give Co-(DTL1)₃ ( 1 ), Co-(DTL2)₃ ( 2 ), Co-(DTL3)₃ ( 3 ), Co-(DTL4)₃ ( 4 ), Co-(DTL5)₃ ( 5 ) and Co-(DTL6)₃ ( 6 ). All the dithiocarbamates and complexes were characterized using ¹H NMR, ¹³C NMR, Fourier transform infrared, UV–visible and mass spectra and the purity confirmed by elemental analysis. In addition, crystal structures of complexes 1 , 2 , 4 and 5 were determined, confirming the formation of mononuclear species in which the Co(III) centers coordinated to six sulfur atoms from three dithiocarbamate ligands resulting in distorted octahedral geometries. All complexes showed moderate to good antibacterial activities against Gram-negative bacteria Escherichia coli, Salmonella typhimurium, Klebsiella pneumoniae and Pseudomonas aeruginosa even at low concentrations. None of the six were active against Gram-positive bacterium methicillin-resistant Staphylococcus aureus and only active against S. aureus at high concentrations. Complexes 5 and 6 were found to be more active than ciprofloxacin against S. typhimurium, E. coli, P. aeruginosa and K. pneumoniae and complexes with chloro-substituted ligands generally had enhanced activities. Antioxidant activities of the dithiocarbamate salts and their Co(III) complexes were also investigated using DPPH assay and the complexes were found to be more efficient. Complex 2 with an IC₅₀ value of 2.84 × 10⁻⁴ mM displayed the highest activity of all compounds tested, even outdoing ascorbic acid. The radical scavenging ability of the complexes followed the order 2 > 1 > ascorbic acid > 3 > 4 > 6 > 5 .     

Carboxymethylcellulose (CMC)–hydroxyethylcellulose (HEC) based hydrogels: synthesis and characterization

A novel carboxymethylcellulose (CMC)–hydroxyethylcellulose (HEC)-based hydrogel with sensitivity to environmental changes, pH and salts was synthesized by using fumaric acid and malic acid at various concentrations. Water uptake capacity of hydrogels was investigated in distilled water, various salt and pH solutions. From pH-dependent studies, it was found that greater water uptake values were observed at greater pH values (7.4), and reversible pH responsiveness of CMC–HEC based hydrogels was obtained. Decreasing the water uptake capacity with increasing of the charge of the metal cation (Al³⁺ < Ca²⁺ < Na⁺) demonstrated metal ion responsiveness of CMC–HEC-based hydrogels. From tensile tests of the hydrogels, a greater crosslinker concentration led to greater tensile strength values. Thermogravimetric analysis and scanning electron microscopy images were used to determine the thermal stability and to observe morphological properties of the samples, respectively.     

Spectroscopic investigations (FTIR,UV-VIS,NMR) and DFT calculations on the molecular structure of Nω-Nitro-L-arginine

The spectroscopic properties of N_ω-nitro-l-arginine were investigated by FT-IR, UV-VIS, and ¹H NMR spectra. Geometrical parameters and energies were calculated using the density functional theory (DFT) B3LYP method with the 6-311G basis set. Geometrical optimization of the molecule has been performed, vibrational spectra have been calculated, and fundamental vibrations have been determined from the total energy distribution (TED) of the vibrational modes. The HOMO-LUMO analysis is carried out for various electric fields (0.0–0.025 A^?1). The HOMO-LUMO gap is decreased while increasing the electric field. The calculated quantum chemical parameters are calculated and correlated to the inhibition efficiency, A Mullliken population was also important for determining local reactivity by indicating reactive centers and identifying potential nucleophilic and electrophilic attack sites. Charge transfer occurs inside the compound based on the HOMO LUMO gap. Calculations of DFT were evaluated in their ability to predict inhibition efficiency.     

Uranyl peroxide ((UO2)(O2)·4H2O; UO4) precipitation for uranium sequestering: formation and physicochemical characterization

Journal of Radioanalytical and Nuclear Chemistry - Applicability of uranium peroxide ((UO2)(O2)·4H2O; UO4) precipitation to remove uranium from secondary wastewaters, generated as part of a...     

New methodology for the characterization of (±)-anti-BPDE-DNA adducts and tetrol I-1 with solid-matrix phosphorescence

Novel solid-matrix phosphorescence (SMP) methods were developed for the detection and characterization of (±)-anti-benzo[a]pyrene-trans-7,8-dihydrodiol-9,10-epoxide ((±)-anti-BPDE)-DNA adducts and a hydrolysis product of the (±)-anti-BPDE-DNA adducts, tetrol I-1, by using the heavy-atom salts, thallium nitrate and sodium iodide, to enhance the solid-matrix phosphorescence. Thallium nitrate was much more effective for enhancing the SMP of the (±)-anti-BPDE-DNA adducts and tetrol I-1. Thus, the results from TlNO₃ were emphasized. The amount of TlNO₃ adsorbed on the solid matrix was varied over a wide range, and SMP intensities, lifetimes, and spectra were acquired. Fundamental equations and calculated photophysical parameters were used to interpret the data and characterize the samples. The data indicated that there were two major populations of the (±)-anti-BPDE-DNA adducts and tetrol I-1 adsorbed on the solid matrix. Because DNA was adsorbed so strongly to the solid matrix, the (±)-anti-BPDE-DNA adducts interacted in a uniform manner with increasing amounts of TlNO₃. However, tetrol I-1 responded in a more random fashion with the increase in the amount of TlNO₃. The methods developed can be used to compare the SMP of small molecular-weight metabolites and DNA samples modified at different levels of (±)-anti-BPDE. Also, the methodology can be employed for DNA samples that are adducted with any material that would give measurable SMP.