S-Adenosyl methionine/S-adenosyl-L-homocysteine ratio determination by capillary electrophoresis employed as a monitoring tool for the antiviral effectiveness of adenosine analogs

S-Adenosyl-L-homocysteine hydrolase (SAHh) inhibitors have long been used as broad-range antivirals and have been recently evaluated as an experimental therapy of filovirus infections. In response to the need for a rapid laboratory testing method that could assess antiviral potency in vivo, our group developed a capillary electrophoresis (CE) method for the determination of the S-adenosyl-L-homocysteine (SAH) to S-adenosyl-L-methionine (SAM) ratio. After chloroacetaldehyde derivatization, SAH and SAM were detected using laser-induced fluorescence detection with a HeCd laser. Separation and quantitation of both SAH and SAM in human plasma were achieved in less than 1 min. The proposed method is rapid and reliable, and could be easily applied to routine monitoring of clinical and preclinical trials subjects.     

The hydrogen salicylate ion as ligand. Complex formation equilibria with dioxouranium (VI), neodymium (III) and lead (II)

The complexation equilibria of the hydrogen salicylate ion, HL(-), have been studied, at 25 degrees C, by potentiometric measurements with a glass electrode in 1 M NaClO4 for uranyl and Nd(III) ions and in 3 M NaClO4 for Pb(II) ion. The ligand concentration (CL) was varied between 10(-3) and 0.05 M. In the system with U(VI) the concentrations ranged between: 10(-3) < or = [U(VI)] < or = 0.01 M, 0.5 < or = CL /[U(VI)] < or = 10 and 10(-2) < or = [H+] < or = 10(-5) M; for neodymium system: 2 x 10(-3) < or = [Nd(III)] < or = 0.01, 1 < or = CL /[Nd(III)] < or = 10 and 10(-2) < or = [H+] < or = 10(-7) M; for lead system: 10(-3) < or = [Pb(II) < or = 3 x 10(-3), 1 < or = CL /Pb(II)] < or = 2 and 10(-5) < or = [H+] < or = 10(-7.3) M. The experimental data have been explained with the formation of UO2HL+, UO2L, UO2(OH)L(-), (UO2)2(OH)L2(-) UO2(HL)L(-), NdHL(2+), NdL(+), Nd(OH)L, PbHL(+), PbL and PbL2(2-). Equilibrium constants are given for the investigated ionic media and at infinite dilution.     

[(4,4‐Dimethyl‐2‐oxo‐1,3‐oxazolidin‐3‐yl)methyl]phosphonic acid

The title compound, C₆H₁₂NO₅P, was synthesized as an inter­mediate phase in a search for new N‐(phosphono­methyl)glycine derivatives. The mol­ecules are held together by O—H⋯O hydrogen bonds, forming chains along the b axis in the crystal structure. The observed mol­ecular structure is compared with that calculated by the density functional theory method.     

Lower rim substituted tert-butylcalix[4]arenes. Part 8: Calix[4]arenes with dialkoxyphosphoryl functions. Synthesis and complexing properties

New compounds: 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis(3-diisopropoxyphosphorylpropoxy)calix[4]arene (1) and 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis(3-methoxyethoxyphosphorylpropoxy)calix[4]arene (2) were synthesized and their ionophoric properties in ion-selective membrane electrodes were studied in comparison with already described by us 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis(3-diethoxyphophorylpropoxy)calix[4]arene (3). Complexes of 1 with calcium(II), lanthanum(III), europium(III) and gadolinium(III) nitrates were prepared in direct reaction of the ligand and appropriate metal salts. They were characterized by spectral data (IR, UV/Vis, luminescence, NMR, ESI-MS) and elemental analysis. The similarity in complexing behavior of the (dialkoxyphosphoryl)propoxy-calix[4]arenes toward calcium and some lanthanides was observed.     

Complex formation equilibria of L-Amino-Acid amides with copper(II) in aqueous solution

Protonation and Cu(II) complexation equilibria of L -phenyhilaninamide, N²-methyl-L-phenylalaninamide, N², N²-dimethyl-L-phenylalaninamide, L -valinamide, and L -prolinamide have been studied by potentiometry in aqueous solution. The formation constants of the species observed, CuL²⁺, CuL, CuLH, CuL₂H and CuL₂H_?2, are discussed in relation to the structures of the ligands. Possible structures of bisamidato complexes are proposed on the ground of VIS and CD spectra. Since Cu(II) complexes of the present ligands (pH range 6–8) perform chiral resolution of dansyl- and unmodified amino acids in HPLC (reversed phase), it is relevant for the investigation of the resolution mechanism to know which are the species potentially involved in the recognition process.     

The rise of lignin biorefinery

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Rhenium(I)-induced cyclization of thiosemicarbazones derived from beta-keto esters

The reactions of methylacetoacetate and ethyl 2-methylacetoacetate thiosemicarbazones (H(2)L(A) and H(2)L(B), respectively) with [ReX(CO)(5)] and [ReX(CO)(3)(CH(3)CN)(2)] (X = Cl, Br) were explored under various experimental conditions. Besides the adducts fac-[ReX(CO)(3)(H(2)L)], in which the rhenium is coordinated to three carbonyl groups, the X anion, and the N,S-bidentate thiosemicarbazone ligand, the following complexes were also isolated: fac-[ReBr(CO)(3)(Hpyz(B))], the tetrameric complexes fac-[Re(pyz(A))(CO)(3)](4) and fac-[Re(pyz(B))(CO)(3)](4), and fac-[Re(pyz(B))(CO)(3)(H(2)O)] (where Hpyz(A) and Hpyz(B) are pyrazolones derived by cyclization of H(2)L(A) and H(2)L(B), respectively). The cyclization reactions were monitored by (1)H NMR spectroscopy and the complexes isolated were identified by elemental analysis, mass spectrometry, IR and (1)H NMR spectroscopy, and in some cases by X-ray diffractometry. The isolation and the full structural identification of the rather unusual fac-[ReBr(CO)(3)(Hpyz(B))], which contains the enol form of the pyrazolone ligand, affords new insight into the cyclization of thiosemicarbazones derived from beta-keto esters.     

Synthesis of 4,5-dihydro-2,4-benzoxazepin-3( 1H)ones and 1,3,4,5-tetrahydro-2,4-benzoxazepines

o- Aminomethylbeiizyl alcohols (X) easily cyclize with phosgene in an aqueous alkaline medium to form 4,5-dihydro-2,4-benzoxazepin-3(1H)ones (IV) and with aldehydes in acidic conditions to yield 1,3,4,5-tetrahydro-2,4-benzoxazepines (V). The characteristics and chemical behaviour of these new heterocyclic ring systems are reported.     

Potential-energy surface, dynamics of van der Waals motions, and vibronic transitions in p-difluorobenzene-argon complex

The dynamics of van der Waals vibrational motions and vibronic spectrum of the complex of argon with p-difluorobenzene (ArDFB) are investigated using the ab initio method. The electronic ground-state potential-energy surface of the complex is calculated at the second-order M?ller-Plesset level of theory using a well-balanced basis set aug-cc-pVDZ and its reduced version without tight polarization functions. The dissociation energy of 351 cm(-1) and the binding energy of 402 cm(-1) determined at the Ar distance of 3.521 Angstroms from the DFB ring well agree with the experimental data available. The character of calculated vibrational levels is analyzed and the effect of a strong coupling between the stretching and bending motions is investigated. A new class of hybrid states created by this coupling is found. To investigate the vibronic S(1)-S(0) spectrum, the surfaces of the electronic transition dipole moment are calculated using the ab initio method. From these surfaces, the vibronic transition intensities are determined and employed to assign the Franck-Condon- and Herzberg-Teller-induced transitions.     

Optically active imidazole N-oxides derived from l-prolinamine1

Starting with (S)-1-benzylprolinamine and α-hydroxyimino ketones, enantiomerically pure bisheterocyclic imidazole N-oxides bearing the (S)-configured N-benzyl(pyrrolidin-2-yl)methyl residue were prepared. These N-oxides reacted with 2,2,4,4-tetramethylcyclobutane-1,3-dithione to give the corresponding optically active imidazole-2-thione derivatives via a sulfur transfer reaction. Reduction of the N-oxides with Raney-nickel led to deoxygenation, whereas catalytic hydrogenation (Pd/C) in ethanol occurred with simultaneous deoxygenation and debenzylation, leading to optically active 1-(pyrrolidin-2-yl)methyl-1H-imidazoles. Alkylation of the prepared imidazole N-oxides and their respective imidazoles with butyl and hexyl bromide and subsequent anion exchange gave optically active N-alkoxy- and N-alkylimidazolium tetrafluoroborates, respectively, with the properties of ‘room temperature ionic liquids’.