Electronegativity and resonance parameters from the geometry of monosubstituted benzene rings

Reference values of the structural substituent parameters, S _E and S _R, measuring the electronegativity and resonance effects, respectively, of functional groups (Campanelli et al. J Phys Chem A 107:6429–6440, 2003) have been determined from the benzene ring geometries of 100 Ph–X species, including different conformations of the same molecule. Geometries have been obtained by quantum chemical calculations at the HF/6-31G*, HF/6-311++G**, and B3LYP/6-311++G** levels of theory. The substituent parameters from HF/6-311++G** calculations are in close agreement with those determined at the HF/6-31G* level. Using the B3LYP density functional yields S _E and S _R values which—in general—correlate well with the corresponding HF values. Exceptions occur with some charged groups, and, in the case of S _E, with a few dipolar groups having very high or low electronegativities. S _R values from B3LYP calculations are about 22% smaller than the corresponding HF values. The variations of the benzene ring geometry caused by electronegativity, resonance, and steric effects are illustrated in some detail.     

Spicachlorantins G-J, new lindenane sesquiterpenoid dimers from the roots of Chloranthus spicatus

Four new lindenane sesquiterpenoid dimers, spicachlorantins G-J (1-4), were isolated from the roots of Chloranthus spicatus together with seven known compounds, including chloramultilide A, shizukaol B, shizukaol D, shizukaol F, shizukaol P, chlorahololide D, and cycloshizukaol A. The planar structures of the new compounds were established by 1D-, 2D-NMR, and MS analyses. The absolute configurations of these compounds were determined by analyzing rotating Overhauser enhancement and exchange spectroscopy (ROESY) and circular dichroism (CD) spectra.     

Quantitative analysis by comprehensive two-dimensional gas chromatography using interval Multi-way Partial Least Squares calibration

A new approach for target quantitative analysis for comprehensive two-dimensional gas chromatography (GC × GC), interval Multi-way Partial Least Square (iNPLS) is presented and evaluated in this paper. In iNPLS, the two-dimensional chromatogram is split in small sections; each of these pieces is treated as an independent new chromatogram. Separated conventional NPLS calibration models for the concentration of the target analyte are built for each of the pieces of the whole chromatogram, and the best model is selected for quantitative analysis. An algorithm for iNPLS running on MatLab platform was written, preliminarily evaluated with using solutions of model compounds with different chemical properties and subsequently applied to quantify some allergens in perfume samples. The results were found to be adequate, and good precision and accuracy was obtained even for poorly resolved peaks.     

Specific crystal structure of poly(3-hydroxybutyrate) thin films studied by infrared reflection–absorption spectroscopy

Infrared reflection–absorption (IR-RAS) and transmission spectra were measured for poly(3-hydroxybutyrate) (PHB) thin films to explore its specific crystal structure in the surface region. As IR-RAS is sensitive to the vibration mode of perpendicular orientation of the surface, differences between IR-RAS and transmission spectra indicate an orientation of the lamella structure in the surface of PHB thin films. The relative intensity of the crystalline CO stretching band in the IR-RAS spectrum is significantly weaker than that in the transmission spectrum. It may be concluded that the transient dipole moment of the CO stretching mode of the crystalline state is not oriented perpendicular but nearly parallel to the substrate surface. On the other hand, the relative intensity of the band at 3009 cm⁻¹ due to the C–H stretching mode of the C–HOC hydrogen bonding is similar between the IR-RAS and transmission spectra, suggesting that the C–H bond is oriented neither perpendicular nor parallel to the substrate surface but in an intermediate direction. Since the CO group of the C–HOC hydrogen bonding is oriented nearly parallel to the surface and its C–H group is in the intermediate direction, it is very likely that the C–HOC hydrogen bonding has a somewhat bent structure. These results are in good agreement with our previous conclusion that the C–HOC hydrogen bonding of PHB exists along the a-axis (not the b-axis) between the CH₃ group of one helix and the CO group of another helix.     

Myrmekiosides a and b, novel mono-o-alkyl-diglycosylglycerols reversing tumor cell morphology of ras-transformed cells from a marine sponge of myrmekioderma sp

Novel mono-O-alkyl-diglycosylglycerols named myrmekiosides A (1) and B (2) were isolated from a marine sponge of Myrmekioderma sp. and their absolute stereostructures were elucidated on the basis of chemical and physicochemical evidence. Myrmekiosides A (1) and B (2) reversed the phenotype of melanoma H-ras transformed NIH3T3 cells at 5 μg/ml.     

Properties of phosphorothioate DNA analogs. An ab initio study of prototype model linkages derived from dimethyl-phosphate anion

Ab initio HF and MP2 calculations on prototype model linkages of phosphorothioate DNA backbones illuminate the effects of phosphorothioation on electronic and structural properties of DNA backbone. The replacement of a bridging oxygen atom by sulfur in the phosphodiester linkage is energetically favored over that of replacement of a non-bridging oxygen atom. In phosphorothioate derivatives containing the P(OS)_nb moiety, the non-bridging oxygen atom always bears a higher negative charge than the non-bridging sulfur. Additional calculations on protonated (neutral) adducts suggest that phosphorothioation of the phosphodiester linkage lowers its proton affinity. Moreover, protonation of the non-bridging oxygen atom at phosphorous is favored over the protonation of the non-bridging sulfur atom for linkages containing the P(OS)_nb moiety. The ab initio calculated structural parameters are compared to the available crystallographic data of small phosphorothioate molecules and phosphorothioate oligodeoxynucleotides. These results have implications upon the biological activity of phosphorothioate DNA analogs.     

Synthesis of stable ruthenium carbonyl complexes containing alkynols ligands and 2(diphenylphosphino)ethyl-triethoxysilane: novel complexes to anchor on mesoporous silica SBA-15 and Al2O3 surface

Abstract  

The triruthenium complexes containing alkynols ligands have been reacted with 2(diphenylphosphino)ethyl-triethoxysilane (dpts), obtaining novel chemically stable disubstituted complexes. The same disubstituted Ru complexes above described were also synthesized following another approach based on the reaction from the phosphine substituted complex Ru₃(CO)₁₀(dpts)₂ and the same alkynols ligands used to obtain the above triruthenium complexes. One of these stable complexes, the HRu₃(CO)₇[C≡C(Me)₂(OH)](dpts)₂ compound was grafted on the mesoporous silica SBA-15 and on γ-Al₂O₃ surface in order to obtain novel hybrid materials to employ in heterogeneous catalysis. The resulting materials have been characterized by multidisciplinary approach based on inductively coupled plasma-mass spectrometry (ICP-MS), FT-IR, XRD, physisorption measurements and DR-UV–Visible spectroscopy.     

12-Acylindolo[1,2-c]quinazolines by palladium-catalyzed cyclocarbonylation of o-alkynyltrifluoroacetanilides

6-Trifluoromethyl-12-acylindolo[1,2-c]quinazolines are prepared in high yield through the palladium-catalyzed reaction of bis(o-trifluoroacetamidophenyl)acetylene with aryl or vinyl halides and triflates. The reaction, which tolerates a variety of important functional groups, probably involves the formation of a 3-acyl-2-(o-trifluoroacetamidophenyl)indole intermediate, followed by its cyclization to the indoloquinazoline product. [reaction: see text]     

A liquid crystal derived from ­ruthenium(II,III) and a long‐chain carboxylate

The title compound, catena‐poly[[tetrakis(μ‐decanoato‐κ²O:O′)diruthenium(II,III)(Ru—Ru)]‐μ‐octanesulfonato‐κ²O:O′], [Ru₂(C₁₀H₁₉O₂)₄(C₈H₁₇O₃S)], is an octane­sulfonate derivative of the mixed‐valence complex diruthenium tetradecanoate. The equatorial carboxyl­ate ligands are bidentate, bridging two Ru atoms to form a dinuclear structure. Each of the two independent dinuclear metal complexes in the asymmetric unit is located at an inversion centre. The octane­sulfonate anion bridges the two dinuclear units through axial coordination. The alkyl chains of the carboxyl­ate and sulfonate ligands are arranged in a parallel manner. The global structure can be seen as infinite chains of polar moieties separated by a double layer of non‐polar alkyl groups, without interdigitation of the alkyl chains.     

A pyrazine bis‐adduct of a binuclear rhodium(II) carboxylate containing 3,4,5‐triethoxybenzoate as the ­equatorial ligand

The title compound, tetrakis(μ‐3,4,5‐triethoxy­benzoato‐κ²O:O′)­bis­[(pyrazine‐κN)­rhodium(II)](Rh—Rh), [Rh₂(C₁₃H₁₇O₅)₄(C₄H₄N₂)₂], crystallizes on an inversion centre in the triclinic space group . The equatorial carboxyl­ate ligands bridge the two Rh^II atoms, giving a binuclear lantern‐like structure. The pyrazine mol­ecules occupy the two axial coordination sites. The phenyl rings are tilted by ca 10° with respect to the attached carboxyl­ate groups. The pyrazine planes have a torsion angle of ca 19° around the Rh—N bond with respect to the plane of the nearer carboxyl­ate group and are not coplanar with the Rh—Rh bond.