Benzoyl(acetylacetonato)nickel(II) complexes containing tertiary phosphine ligands. Their synthesis,dynamic behavior in solution,and decarbonylation

Carbon monoxide is readily inserted into the phenyl—nickel bond of PhNi(acac)(PR₃)_n to give benzoylnickel complexes, PhCONi(acac)PR₃ (R = Ph, Et, cyclo-C₆H₁₁), which were characterized by elemental analysis, IR and NMR spectroscopy, as well as chemical reactions. The reactions of the benzoylnickel complexes with methyl iodide and alcohols give acetophenone and corresponding benzoates, respectively, accompanied by some decomposition reactions. The solid benzoylnickel complexes when heated at elevated temperatures are decarbonylated and biphenyl, benzophenone and carbon monoxide are liberated. The dynamic behavior of the acac ligand in acetone solution was studied and the activation parameters for the acac exchange reactions were obtained. The decarbonylation reaction of the benzoyl complex PhCONi(acac)PPh₃ in acetone was studied by NMR, and found to be first order in the benzoylnickel complex.     

Fluorocinnoline derivatives. II. Synthesis and antibacterial activity of fluorinated 1-alkyl-1,4-dihydro-4-oxocinnoline-3-carboxylic acids

Chemical modification of cinoxacin was studied with the aim of improving its antibacterial activity and spectrum. Alkylation of ethyl 6,7,8-trifluoro- and 6,7-difluoro-4-hydroxycinnoline-3-carboxylates (1 and 7) with alkyl iodide or dialkyl sulfate gave ethyl 1-alkyl-6,7,8-trifluoro- and 6,7-difluoro-1,4-dihydro-4-oxocinnoline-3-carboxylates (2 and 8), together with the isomeric anhydro-bases 3 and 9 of 2-alkyl-3-ethoxycarbonyl-6,7,8-trifluoro- and 6,7-difluoro-4-hydroxycinnolinium hydroxides, respectively. Acid-catalyzed hydrolysis of the 1-alkyl derivatives 2 and 8 gave the corresponding carboxylic acids 4 and 10. The same treatment of 3 and 9, accompanied with decarboxylation of the inner salts 5 and 11, afforded the anhydro-bases 6 and 12 of 2-alkyl-4-hydroxycinnolinium hydroxides, respectively. Displacement reactions of 4 and 10 with nucleophiles such as amine, alkoxide and thiolate gave 7-substituted 1-alkyl-6,8-difluoro- and 6-fluoro-1,4-dihydro-4-oxocinnoline-3-carboxylic acids (13 and 17-35). Antibacterial activities of these compounds were evaluated and compared with those of cinoxacin and norfloxacin. Some compounds showed a broader spectrum and more potent activity than cinoxacin, but were considerably inferior in activity to norfloxacin.     

Isolation, characterization, and theoretical study of La2@C78

A new metallofullerene, La2@C78, has been synthesized by DC arc discharge method, isolated by high-performance liquid chromatography, and characterized by laser desorption time-of-flight mass spectrometry, UV-vis-NIR absorption, differential pulse voltammetry, 13C NMR spectroscopy, and theoretical calculations. The La2@C78/CS2 solution is dark violet and presents several characteristic absorption features at 647, 561, 533, and 386 nm, with an onset around 1000 nm. With respect to empty D3-C78, the capability of La2@C78 as an electron acceptor or donor is stronger. Addition of 1,1,2,2-tetrakis(2,4,6-trimethylphenyl)-1,2-disirane to La2@C78 photochemically, as well as thermally, affords bis- and mono-adducts. Theoretical studies and 13C NMR spectroscopic analysis of La2@C78 indicate that it possesses a D3h-C78 cage (78:5).     

Pressure effects on the phase transition of urea adducts withn-paraffins and polyethylene

The decomposition of urea adducts with hydrocarbons is treated as a first-order phase transition and the pressure dependence is studied up to 0.7 GPa for several kinds of adducts. The thermodynamic quantities at the decomposition of the adduct can be analysed as a sum of those quantities of the component materials. The transition from the orthorhombic to the hexagonal form of the adduct with polyethylene is also investigated by X-ray diffraction and the pressure dependence of the lattice parameters is measured for the adducts. The results are compared with the phase transition in the pure paraffin.     

Synthesis of glutamate by reductive amination of 2-oxoglutarate with the combination of hydrogenase and glutamate dehydrogenase

Glutamate synthesis by reductive amination of 2-oxoglutarate was performed by the combination of NADH regeneration system and glutamate dehydrogenase (GluDH). The conversion of 2-oxoglutamate to glutamate was 98% after 3 h, and the turnover number of NAD⁺was 17.     

C-H to N substitution dramatically alters the sequence-specific DNA alkylation, cytotoxicity, and expression of human cancer cell lines

We designed and synthesized sequence-specific alkylating conjugates 1 and 2, which selectively alkylate matched sequences at nanomolar concentrations. Conjugates 1 and 2 differ only in that the C-H is substituted by an N in the second ring, which precisely recognizes and effectively alkylates DNA according to the recognition rule of Py-Im polyamides. We investigated sequence-specific DNA alkylation, cytotoxicity in 39 human cancer cell lines, and the effect on expression levels in cancer cell lines by Py-Im conjugates 1 and 2. The COMPARE analysis of the mean graphs showed that conjugates 1 and 2 did not correlate well with each other (r = 0.65) despite having a common DNA alkylating mechanism (purine N3 alkylation). Array-based gene expression analysis demonstrated that there are several oppositely regulated genes. The results suggest the intriguing possibility that DNA alkylating agents recognizing longer base-pair sequences may provide a promising approach for developing new types of antigene agents.     

Chemical reaction dynamics of PeCB and TCDD decomposition: A tight‐binding quantum chemical molecular dynamics study with first‐principles parameterization

The decomposition reaction dynamics of 2,3,4,4′,5‐penta‐chlorinated biphenyl (2,3,4,4′,5‐PeCB), 3,3′,4,4′,5‐penta‐chlorinated biphenyl (3,3′,4,4′,5‐PeCB), and 2,3,7,8‐tetra‐chlorinated dibenzo‐p‐dioxin (2,3,7,8‐TCDD) was clarified for the first time at atomic and electronic levels, using our novel tight‐binding quantum chemical molecular dynamics method with first‐principles parameterization. The calculation speed of our new method is over 5000 times faster than that of the conventional first‐principles molecular dynamics method. We confirmed that the structure, energy, and electronic states of the above molecules calculated by our new method are quantitatively consistent with those by first‐principles calculations. After the confirmation of our methodology, we investigated the decomposition reaction dynamics of the above molecules and the calculated dynamic behaviors indicate that the oxidation of the 2,3,4,4′,5‐PeCB, 3,3′,4,4′,5‐PeCB, and 2,3,7,8‐TCDD proceeds through an epoxide intermediate, which is in good agreement with the previous experimental reports and consistent with our static density functional theory calculations. These results proved that our new tight‐binding quantum chemical molecular dynamics method with first‐principles parameterization is an effective tool to clarify the chemical reaction dynamics at reaction temperatures. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

Study of salt permeation process into Vigna angularis using Ag/AgCl electrodes

In this work we report a novel method that can monitor in vivo the salt permeation process into a plant Vigna angularis using two Ag/AgCl electrodes. The method is based on the electromotive force (emf) measurement using two Ag/AgCl electrodes, one inserted into the V. angularis pith cavity and the other placed into saline ([NaCl]=1 M) surrounding the roots. Temporary change of emf ranging from 0 to ca. 0.115 V was measured in vivo using the system, and the possible physiological phenomenon during the period was discussed.     

Synthesis of alanine and leucine by reductive amination of 2-oxoic acid with combination of hydrogenase and dehydrogenase

Alanine synthesis by reductive amination of pyruvate was performed by the combination of NADH regeneration system and alanine dehydrogenase (AlaDH). The conversion of pyruvate to alanine was 99% after 1 h. Leucine synthesis was also carried out by the combination of NADH regeneration system and leucine dehydrogenase (LeuDH). The conversion of 4-methyl-2-oxovalerate to leucine was 60% after 1.5 h.