Neoflavones. 1. Natural Distribution and Spectral and Biological Properties

Data on neoflavones isolated from 58 plants belonging to the Clusiaceae, Fabaceae, Rubiaceae, Thelypteridaceae, Passifloraceae, Asteraceae, and Rutaceae families from the literature up to 2002 were systematized and reviewed. A list of 131 4-phenylcoumarins with information on the plant sources, structures, physicochemical data, and pharmacological properties with references to the original literature was composed.     

Electrophilicity and nucleophilicity in singlet carbenes. I. dependence on electronegativity.

Based on one-electron perturbation theory the electrophilic and nucleophilic reactivity of a single carbene :CX₂ depends (a) on the electronegativity of X and (b) on its position in the periodic table (first row versus second row).     

The tube electrode and e.s.r.

The convective diffusion equation for the downstream distribution of products and intermediates produced on a tube electrode under conditions of laminar flow is solved. For distances which are large compared to the thickness of the electrode, an analytical solution in real space can be found. The solution of the equation has been applied to an apparatus in which the intermediates and products are detected by e.s.r. The species are transported by laminar flow from the electrode through an e.s.r. cavity. Results are presented for two systems and are found to be in good agreement with the theory.     

Multivariate calibration. I. Concepts and distinctions

This is the first of two introductory papers on multivariate calibration. We show how precise quantitative chemical analysis is made possible even in 'dirty' sample types like biological tissue, by compensating for systematic interferences in the measured data. This drastically reduces the required sample preparation work, making high-speed, nonspecific instrument measurements possible. Multivariate calibration also allows various types of automatic error detection, improving reliability in chemical analysis.The present paper treats on a conceptual basis the following topics: Univariate vs. multivariate calibration, direct vs. indirect calibration and controlled vs. natural calibration. Some aspects of multivariate quantitative modelling is illustrated, and multiwavelength near infrared spectrometry is given as a practical example. The compromise between necessary complexity vs. danger of statistical overfitting is discussed.     

Polyperfluorobutadiene. II. Fractionation and crosslinking

Perfluorobutadiene was polymerized in bulk under low pressure and temperature in the presence of diisopropyl peroxydicarbonate, bis(trifluoromethyl) peroxide, and benzoyl peroxide. Fractional solvent extraction of polyperfluorobutadiene by n-hexane and hexafluorobenzene into three polymeric fractions was described. The hexafluorobenzene-soluble fraction was used for crosslinking studies. Direct fluorination of solid polyperfluorobutadiene required no catalyst. The fluorine–polyperfluoropolyene reactions furnished a mechanism for crosslinking the unsaturated chains. Fluorination by gaseous fluorine formed free radical sites on the polymer chains besides saturation reactions. The presence of excess monomer in contact with these partially fluorinated solid polyperfluorobutadienes under controlled conditions were capable of crosslinking and grafting to the linear chains. Direct fluorination of solid polyperfluorobutadiene tends to involve reaction with the internal double bonds rather than the pendant perfluorovinyl group; the converse is true for crosslinking with hexamethylenediamine. The mechanisms are discussed.     

N.M.R. and X-ray diffraction of the 7,7'-disodiumcromoglycate-water lyomesophases

Aqueous solutions of 7,7'-disodiumcromoglycate (7,7'-DSCG) form a variety of mesophases, whose natures depend on concentration and temperature. We have used optical microscopy, N.M.R. (of ²H, ¹⁷O and ²³Na) and X-ray techniques to construct a phase diagram for this system and to characterize the various mesophases. In the concentration range 3 to 25 wt % 7,7'-DSCG four different mesophases are found. On cooling the isotropic solution an opaque gel phase is first obtained, followed on further cooling by a birefringent glassy liquid. At concentrations below 14wt% it is nematic, while at higher concentrations it appears to be a different, more ordered, phase. At lower temperatures a hexagonal phase is formed which finally solidifies on cooling to - 15°C. The N.M.R. and X-ray characteristics of these mesophases are discussed.     

Polysiloxane dizwitterionomers. IV. Mechanical and dielectric relaxations

The relaxation behavior of a series of polysiloxane dizwitterionomers has been studied by using dynamic mechanical and dielectric spectroscopy. The temperature range was 100–375 K and the frequency was ca. 1 Hz in the mechanical measurements and 50 Hz–50 kHz in the dielectric measurements. Three relaxation regions, labeled α_s, β, α_z in order of increasing temperature, were observed. The β_s relaxation was assigned to the nonionic portion of the siloxane chain and correlated with the glass transition of polydimethylsiloxane. The β and α_z processes are ionic-related relaxations; β probably originated from the motion of a chain segment carrying a dizwitterion, and α_z, from the collapse of the organization in the ionic domains. Absorbed water exerts a profound influence on relaxation behavior–primarily on α_z ionic relaxation and the relative rigidity of the samples. The water molecules solvate the ions and thus shift the α_z relaxation to lower temperatures. Some aspects of the effect of thermal history on the microphase separation into domains have also been investigated. The results indicate that the organization of the zwitterions in the ionic domains is improved at slow cooling rates.     

HPLC of antibiotics. 1. Streptolydigin and related compounds

Two new acyltetramic acids related to streptolydigin have been isolated from fermentations of Streptomyces lydicus. The principal members of this complex were resolved by TLC on silica gel. However, the methods of detection, permanganate spray or bioautography, were not suitable for both crude fermentation broths and purified extracts. Gas chromatography is unsuitable for the detection of either underivatized or silylated streptolydigins. High performance liquid chromatography (HPLC) particularly on triethylaminoethyl cellulose is rapid and sensitive and is the method of choice for the analysis of both crude and purified samples. Using high performance liquid chromatography, two components were detected in the complex, which are not observed using any of the other chromatographic procedures.     

Piezoelectric polymer films. II. Piezoelectric and pyroelectric evaluation

The concept of piezoelectric and pyroelectric effects in amorphous polymers is presented, with experimental results, details on sample preparation, and activity evaluation. Most evaluations were performed on 25–30 mol% tributyltin methacrylate/methyl methacrylate copolymers, which possessed good piezoelectric activity, antifouling properties, and paint-formulation characteristics. Solvent-induced orientation effects that lead to piezoelectric activity in amorphous, unpoled, polymers are also described.     

Diamagnetic contribution and substituent effects on 13C n.m.r. spectra

Correction of measured chemical shifts by subtracting the diamagnetic contributions caused by certain substituents on various carbons of a molecule leads to data that allow a reasonable interpretation of substituent effects on chemical shifts in ¹³C n.m.r. spectroscopy. It is shown that both paramagnetic and diamagnetic terms increase on all carbons of a molecule when the atomic number of a substituent increases down the same group of the periodic table. An explanation of α-, β-, and γ- effects for methyl substitution using the same procedure is attempted.     

Crystallization characteristics of polymer blends. I. Polyethylene and polystyrene

Blends of polyethylene and polystyrene have been prepared to study the effect of the morphology on their crystallization characteristics since the polymers are known to phase separate. The polymer component present in least amount formed a dispersed phase of discrete spherical particles whose number and size altered with blend composition. However, close to 50% composition cylindrical rods of polyethylene dispersed in polystyrene were observed. With polyethylene in excess the kinetics of crystallization were insensitive to the morphology, but with polyethylene present as the dispersed phase they became dependent on the size and number of the spheres, and in particular on the nucleation density. When the number of spherical particles exceeded that of heterogeneous nuclei, larger supercoolings, and so presumably homogeneous nucleation, were required for crystallization to develop further. The degree of crystallization of the blends then became dependent on the temperature of crystallization rather than on time, and the isothermal crystallization appearing to be instantaneous.     

Legionella moravica sp. Nov. and Legionella brunensis sp. Nov. Isolated from cooling-tower water

Two Legionella-like organisms were isolated from cooling-tower water samples in Czechoslovakia. They were presumptively identified as legionellae by their growth on buffered charcoal-yeast extract agar (BCYE) containing L-cysteine and their absence of growth on BCYE without L-cysteine. Both strains contained predominantly branch-chained cellular fatty acids and were therefore definitively placed in the genus Legionella. They were serologically distinct from other described Legionella species and were shown by DNA studies to constitute two new Legionella species, Legionella moravica (type strain 316-36; ATCC 43877) and Legionella brunensis (type strain 441-1; ATCC 43878).     

Sulfur-containing polymers. II. Preparation and properties of polycarbamoylsulfenamides

Polycarbamoylsulfenamides have been prepared by interfacial and solution polycondensation of chlorocarbonylsulfenyl chloride with diamines. In preparing the polycarbamoylsulfenamides, the following types of diamines were used: primary aliphatic diamines, a mixed primary-secondary aliphatic diamine, primary aromatic diamines, and secondary aromatic diamines. The properties of the resulting polymers depended primarily on the kind of diamines used. Transparent, tough films were obtained from the polymer based on N,N′-dimethyl-4,4′-diaminodiphenylmethane. The photochemical decomposition of the polymers has been studied.     

Synthetic Approaches to cularines. III. Nucleophilic addition and substitution

Attempts to induce the formation of the dibenzoxepine ring of cularine compounds by generating an electron-deficient system in ring C of an 8-hydroxybenzylisoquinoline met with failure. Attack by C-8 phenol on a “p-quinone methide” intermediate afforded benzofurans 16 , which it has been suggested are intermediates in the biogenesis of quettamines. Among the nucleophilic substitution reactions tried, only that based on a phenoxide attack on a benzyne intermediate (generated by dimsyl sodium treatment of a 2′-bromo-8-hydroxybenzylisoquinoline) afforded the dibenzoxepine nucleus of tetradehydrocularines 25 and 27. Competing N-attack afforded the indolizine skeleton present in 24 and 26. From compounds 25 and 27 , the corresponding cularines, cularimines and oxocularines were obtained.     

Trypsin and affinity chromatography.

Affinity adsorbents for trypsin which were prepared by immobilizing product-type ligands, that is, peptides having C-terminal arginine, proved to be effective not only for preparative purposes but also for basic research on molecular recognition. The properties of the binding site of trypsin were revealed by chromatographic experiments. Quantitative analysis based on the theory of frontal affinity chromatography proved to be extremely effective. As an extension of the product-type ligands, peptide argininals were also used and information on the mechanism of action of these inhibitors was obtained. Anhydrotrypsin, which lost the hydroxyl group of Ser183, was found to gain increased binding ability for product-type compounds. This inactivated enzyme was also used as an immobilized ligand and the unique affinity adsorbent thus prepared proved to be extremely effective for the separation of peptides and recombinant proteins based on their C-terminal structures. High-performance affinity chromatography of trypsin and related enzymes using a polymer-based support was also developed.     

The Adsorption of Herbicides and Pesticides on Clay Minerals and Soils. Part 2. Atrazine

The adsorption of atrazine and two model compounds,2-chloropyrimidine and 3-chloropyridine on clay minerals(bentonite, montmorillonite and kaolinite), organic matter (humic acid) and soil (with and without organic matter) has beenstudied using FT-infrared spectroscopy (IR), thermogravimetric analysis (TGA), high pressureliquid chromatography (HPLC) and X-ray diffraction (XRD).3-Chloropyridine, 2-chloropyrimidine and atrazine were adsorbedthrough hydrogen bonding on bentonite, montmorillonite, humic acid and soil. In addition tohydrogen bonding, protonation of 3-chloropyridine and atrazine was also observed.In the adsorption of 2-chloropyrimidine on bentonite and montmorillonitean ion exchange mechanism also occurred. No adsorption of 3-chloropyridine or 2-chloropyrimidine wasobserved on the kaolinite clay mineral.Both the clay minerals and organic matter of soil contribute tothe adsorption of organic compounds on soil but the clay minerals bentonite and montmorilloniteplay a major role in their adsorption on soil.     

Telechelic sulfate ionomers. I. Preparation and solution and thermal properties

New telechelic ionomers with zinc and sodium sulfate salt terminal groups on hydrogenated polybutadiene (HPB) backbones ( I ) were prepared from hydroxyl-terminated hydrogenated polybutadiene (HTHPB) of three different molecular weights (1350, 2100, and 3200 g/mol). Quantitative acid-base titration, elemental analysis, and NMR spectroscopy were used to verify the structure, and further characterization included differential scanning calorimetry (DSC) and solution viscometry. The DSC results indicated that the ionomers are free of impurities within the limit of the resolution of the method. Glass transition temperatures determined by DSC indicated that the elevation in glass transition temperature by ionic crosslinking was most strongly dependent on the molecular weight of the backbone of the telechelic ionomer. The solution viscometry results showed that the sulfation reaction did not cause either covalent crosslinking or chain scission. Furthermore, the solubility characteristics of the sulfate-terminated hydrogenated polybutadiene (STHPB) oligomers were shifted towards a preference for polar solvents by the presence of salt groups. The lower molecular weight ionomers of the series showed polyelectrolyte-like extension at very dilute concentrations in polar solvents. The onset of polymer gelation in hexane was observed for the ionomers which had the highest molecular weight backbones.     

Alkaloids ofNitraria komarovii. XV. Vasicinone and deoxyvasicinone N-oxides

Two new alkaloids have been isolated from the epigeal part ofNitraria komarovii — the N-oxides of vasicinone and of deoxyvasicinone. Their structures have been established on the basis of spectral results and chemical transformations.     

Chemorheology of polyurethane. I. Vitrification and gelation studies

We propose in this article a study of the viscoelastic behavior of reticulated PU systems that are synthesized from a triisocyanate and a polyetherdiol of molar mass 1000 or 2000 g · mol⁻¹. We initially sought to confirm the expected results concerning the phenomenon of gelation, and in particular, that the power law G′ ∼ G″ ∼ ω^Δ is verified. The appearance of a maximum of tan δ on the rheological curves led us to consider a second state of transition, namely vitrification. This could constitute an invaluable source of information on the complex morphology of the final material due to the microheterophased character of PU. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 544–551, 2000     

Vibrational spectra and stereochemistry of mono-and polysaccharides. II. α-anomers of D-glucose and D-galactose. Glucitol and galactitol

The IR and Raman spectra of D-glucose and D-galactose α-anomers are compared with the corresponding spectra of the related polyatomic alcohols glucitol and galactitol. Experimental data on the frequencies and modes of normal vibrations and on the contributions of normal vibrations involving particular skeletal CiOi and CiC(i+1) bonds to the potential energy distribution (PED) are compared with the results of theoretical calculations. The α-anomers of D-glucose and D-galactose with different configurations of the C4C4 and C4H4 bonds are characterized by substantially different sets of frequencies with prevailing contributions to PED from the CiOi and CiC(i+1) bonds. The similar bonds of glucitol and galactitol are also characterized by specific frequency sets. Particular CiOi and CiC(i+1) bonds have different numbers of “localized” frequencies. B. I. Stepanov Institute of Physics, Belarus Academy of Sciences. V. Tshebyatovski Institute of Low Temperatures and Structural Studies, Polish Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 3, pp. 431–442, May–June, 1995. Translated by I. Izvekova