Proanthocyanidins ofPolygonum coriarium. IV. Structures of proanthocyanidins T3 and T4

Two oligomeric proanthocyanidins have been isolated from the roots ofPolygonum coriarium. By a study of their physical properties and spectral characteristics and analysis of the results of chemical transformations, the chemical structures of these compounds have been established as: (–)-epicatechin-77[O--D-glucopyranosyl]₃ O-⊃-D-glucopyranosyl (m-trigallolyl)-[(4-6)-(–)-epigallocatechin]₂-(4-6)-(–)-epigallocatechin—T3; and (–)-epicatechin-3-O-galloyl-7-[O--D-glucopyranosyl]₃O--D-glucopyranosyl galloyl-[(4-6)-(–)-epicatechin]₄-(4-6)-(–)-epigallocatechin — T4.The materials of this paper were presented at the IInd International Symposium on the Chemistry of Natural Compounds (SCNC), Eskiehir, Turkey, October 22–24, 1966).Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 707–713, September–October, 1997.     

Nonisothermal membrane phenomena across perfluorosulfonic acid-type membranes,Flemion S: Part II. Thermal membrane potential and transported entropy of ions

Thermal membrane potentials across the perfluorosulfonic acid-type membrane, Flemion S, were measured for HCl, alkali metal chlorides, and ammonium and methyl ammonium chlorides. The difference between the mean molar transported entropy of the counterions in the membrane and the partial molar entropy of the counterions in the external solution was determined from the experimental data on thermal membrane potential, thermoosmosis and electroosmosis. The sign of the thermal membrane potential in HCl solution varies from positive to negative with the concentration. In HCl and alkali metal chloride solutions, the order of their thermal membrane potentials (–/T) is H⁺>Li⁺=Na⁺>K⁺ which is roughly the inverse of that of the crystallographic radii of the ions. However, the order of their entropy differences is H⁺>Na⁺>K⁺>Li⁺ which is just the inverse of that of their thermoosmotic coefficients (D) or the entropy difference of water in thermoosmosis. For the ammonium and methyl ammonium ion forms, the orders of both –/T and increase with an increasing number of methyl groups: (CH₃)₄N⁺>(CH₃)₃NH⁺>(CH₃)₂NH ₂ ⁺ > CH₃NH ₃ ⁺ >NH ₄ ⁺ , which is also the inverse of that ofD or .     

New Data on the Crystal Structures of Colusites and Arsenosulvanites

The crystal structures of three minerals (arsenosulvanite, V,As-germanite, and colusite) of the general crystal chemical formula (As, Ge, Sn, Sb, V)₆S₃₂, where Cu^M, V^M are cations at interstitial positions, 0.2 x 2.0, 2.7 y 0, (space group , a = 10.527; 10.600; 10.653 ; R = 0.066; 0.046; 0.033) have been determined using single-crystal X-ray diffraction data. The minerals are the two structural modifications of the compound with the ideal formula V₂Cu₂₄As₆S₃₂; they differ from each other in the occupancy of the interstitial position 2a. In colusite, this position is occupied by the V⁵⁺ cations; in arsenosulvanite and V,As-germanite, by Cu²⁺. A characteristic feature of the structures is the presence of octahedral [ S₄]Cu₆ ( = V, Cu) complexes not directly interacting with each other and lying inside the Laves polyhedra. In the structures of arsenosulvanite and V,As-germanite, a sulvanite framework consisting of interpenetrating Laves polyhedra T₃S₄ ( = V, Cu; T = Cu, As, Ge) has been found. The sulvanite framework is statistically distributed over the sphalerite matrix. The variable composition of the minerals is due to heterovalent isomorphism in the sphalerite position 6c. Charge disbalance arising from substitution of the pentavalent arsenic cations by cations of lower valence is compensated by the appearance of additional Cu²⁺ cations. The nonstoichiometry of the compositions is explained by the presence of vacancies in the interstitial and sphalerite positions.     

Stereospecific coordination ofl-hydroxyproline esters with triosmium clusters

The reactions of cluster (-H)Os₃(CO)₁₀(-OH) with ethyl and isopropyl esters ofl-oxyproline were studied. In the presence of Me₃NO intermediate complex (-H)Os₃(CO)₉(-OH)L (L — isopropyl ester ofl-oxyproline) is formed, which slowly converts to the more stable cluster (-H)Os₃(CO)₉ . Cluster complexes containing chelate-bridging heterocycles were also obtained by heating (-H)Os₃(CO)₁₀(-OH) with esters ofl-oxyproline. In both cases, only one of the possible diastereomeric complexes (-H)Os₃(CO)₉ (R = Et, Prⁱ) is formed, which indicates that the reactions are stereospecific. Based on analysis of Dreiding's models, an attempt to determine the absolute configuration of the obtained clusters was made.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2021–2025, October, 1995.     

Dissociation Constants of Protonated Cysteine Species in NaCl Media

The sulfur-containing biomolecule, cysteine has a role in physiological and natural environment because of its strong interactions with metals. To understand these interactions of metals with cysteine, one needs reliable dissociation constants for the protonated cysteine species [ CH(CH₂SH)COOH; H₃B⁺]. The values of dissociated constants, p , for protonated cysteine species (H₃B⁺ H⁺ + H₂B, K ₁; H₂B H⁺ + HB^–,K ₂; HB^– H⁺ + B^2–,K ₃) were determined from potentiometric measurements in NaCl solutions as a function of ionic strength, 0.5–6.0 mol-(kgH₂O)^–1 and between 5, and 45°C. The equations

Oligomeric proanthocyanidin glycosides ofClementsia semenovii. II

The structures of proanthocyanidins CS-3 and CS-4, isolated from the roots ofClementsia semenovii have been established on the basis of chemical and spectral studies. CS-3 is 7-O-(6-O-galloyl--D-Glcp O--D-Glcp O--D-Glcp O--D-Glcp O--D-Glcp)-(+)-catechin-(4—8)-(–)-epigallocatechin-(4—8)-(+)-catechin-(4—8)-(–)-epigaLLocatechin-(4—8)-(–)-epigallocatechin-(4—8)-(–)-epigallocatechin, and CS-4 is 3-O-galloyl-7-O-[6-O-galloyl--D-Glcp O--D-Glcp O--D-Glcp-(+)-gallocatechin-(4—8)-[(+)-catechin-(4—8)-(3-O-galloyl-(–)-epigallocatechin]₂-(4—8)-(–)-epicatechin.Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 50–58, January–February, 1999.     

α-Ketothioketene dimers

Conclusions When,-dichlorovinyl ketones are reacted with Na₂S, NaSC(S)N(C₂H₅)₂, KSC(S)OC₂H₅, and NaSCOCH₃, two types of sulfur-containing heterocyclic compounds are formed: 1,3-dithietanes and 1,3-dithiols , at which time the ratio of the products depends on the nature of the sulfur-containing nucleophilic reagent.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2940–2048, September, 1976.     

The thermal decomposition of zirconium oxyhydroxide

The thermal decomposition of zirconium oxyhydroxides prepared by the mixture of aqueous zirconium oxychloride solutions and aqueous solutions of sodium hydroxide or ammonium hydroxide under various conditions has been examined by thermogravimetry, differential thermal analysis, X-ray diffraction study and infrared spectrophotometry. As a result, it is seen that the thermal decomposition of zirconium oxyhydroxide, in which the composition is ZrO_2-x(OH)_2xyH₂O where x2 and 1y<2, proceeds according to the following process:

Mixed-Ligand Complexes Zn(2,2′-Bipy)(ROCS2)2 with Mono- and Bidentate Ligands {\text{ROCS}}_{\text{2}}^ - (R = i-Pr, i-Bu)

The mixed-ligand complexes Zn(2, -Bipy)(i-PrOCS₂)₂ (I) and Zn(2, -Bipy)(i-BuOCS₂)₂ (II) were synthesized. Their structures were solved using the X-ray diffraction data (CAD-4 diffractometer, MoK radiation, 1873 and 1948 F _hkl , R = 0.0357 and 0.0338). The crystals are triclinic with unit cell dimensions a = 10.002(2), b = 11.080(2), c = 11.756(2) , = 78.46(3), = 75.49(3), = 63.50(3)°, V = 1122.9(4) ³, Z = 2, space group (for complex I) and a = 8.760(2), b = 12.520(3), c = 13.252(3) , = 63.93(3), = 71.10(3), = 88.01(3)°, V = 1225.2(5) ³, Z = 2, space group (for II). The structures are based on discrete monomeric molecules. The polyhedra of Zn atoms are tetragonal pyramids (ZnN₂S₃, c.n. 4+1, both bidentate and monodentate ligands coordinated to the Zn atom). The packing of molecules and the character of their interaction in the structures are considered.     

Thermodynamic Properties of Aqueous Dimethylamine and Dimethylammonium Chloride at Temperatures from 283 K to 523 K: Apparent Molar Volumes, Heat Capacities, and Temperature Dependence of Ionization

Data for the apparent molar volumes of aqueous dimethylamine and dimethylammonium chloride have been determined with platinum vibrating tube densimeters at temperatures 283.15 K T 523.15 K and at different pressures. Apparent molar heat capacities were measured with a Picker flow microcalorimeter over the temperature range 283.15 K T 343.15 K at 1 bar. At high temperatures and steam saturation pressures, the standard partial molar volumes of dimethylamine and dimethylammonium chloride deviate towards positive and negative discontinuities at the critical temperature and pressure, as is typical for many neutral and ionic species. The revised Helgeson-Kirkham-Flowers (HKF) model and fitting equations based on the appropriate derivatives of solvent density have been used to represent the temperature and pressure dependence of the standard partial molar properties. The standard partial molar heat capacities of dimethylamine ionization , calculated from both models, are consistent with literature data obtained by calorimetric measurements at T 398 K to within experimental error. At temperatures below 523 K, the standard partial molar volumes of dimethylamine ionization agree with those of morpholine to within 12 cm³-mol^-1, suggesting that the ionization of secondary amine groups in each molecule is very similar. The extrapolated value for of dimethylamine above 523 K is very different from the values measured for morpholine at higher temperature. The difference is undoubtedly due to the lower critical temperature and pressure of (CH₃)₂NH(aq).     

Glass transitions in crosslinked epoxy networks

Epoxy resins of DGEBA type were thermally cured with diaminodiphenylmethane as crosslinking agent, and then analysed by Differential Scanning calorimetry (DSC) at various heating rates in order to determine the glass transition temperatureT _g of the final networks. First it was shown that during cyclingT _g is shifted towards higher values up to a maximum or . Such a change is attributed to an increasing extent of cure which develops during the thermal analysis, and also to relaxation processes thermally activated inside the polymeric matrix. Then the dependence of on the heating rateq imposed by the DSC apparatus was presented forq changing from 0.1 to10C min^–1. At heating rates exceeding 3C min^–1 only the classical temperatureT _g was detected, but at smallerq values, an additional endothermic transition was revealed, located at higher temperature and linked to a physical aging-like phenomenon, which takes place at low heating rates. The plot of against logq is divided into two quasi-linear parts on each side ofq=3C min^–1. In conclusions, an equation was given to describe the vs. logq function.     

Solubility of Oxygen in Some 1-1, 2-1, 1-2, and 2-2 Electrolytes as a Function of Concentration at 25°C

The solubility of oxygen has been measured in a number of electrolytes [(LiCl, KCl, RbCl, CsCl, NaF, NaBr, NaI, NaNO₃, KBr, KI, KNO₃, CaCl₂, SrCl₂, BaCl₂, Li₂SO₄, K₂SO₄, Mn(NO₃)₃)] as a function of concentration at 25°C. The solubilities, mol (kg-H₂O)^–1, have been fitted to a function of the molality m (standard deviation < 3mol-kg^–1)

Reaction graphs and a construction of reaction networks

Summary A general definition of reaction graphs is presented. For a pair of isomeric molecular graphs and , related by a chemical transformation , the reaction graph is determined using a maximal common subgraph defined for vertex mapping . A binary operation defined for graphs constructed over the same vertex set enables us to decompose the reaction graph into the sum of prototype reaction graphs. A decomposition of an overall reaction graph can be advantageously used for the construction of a reaction network. An oriented path in this network beginning at and ending at corresponds to a breakdown of the transformation into a sequence of intermediates.     

Complete synthesis of serratamolide

Summary 1. A method for the separation and quantitative determination of - and -DNP derivatives of , -DABA, ornithine, and lysine has been proposed.2. A quantitative evaluation of the N N migration in four peptides of , -DABA has been carried out.3. The degree of migration in inactive polymyxin M and the DNP-peptides from a partial hydrolyzate of the inactivated antibiotic has been determined.4. The amino acid composition of the DNP peptide B1 from a partial hydrolyzate of active DNP-polymyxin M has been established.5. The quantitative aspect of the conversion of and diketopiperazines has been studied.Khimiya Prirodnykh Soedinenii, Vol. 2, No. 4, pp. 277–284, 1966     

Formation constants in the ternary systems: CuII-dipeptideamino acids

Summary A potentiometric titration technique has been used to determine formation constants for the various complexes of Cu^II with amino acids (L) and dipeptides (B) at 298 K and I-0.1 M (NaClO₄). The structure and mode of bonding in binary and ternary complexes are discussed. Values of log are evaluated. The plots of pK of amino acidsversus log K for the present and the earlier known systems gave an empirical relation: pK=–5.3 log K+10.5.     

The effectiveness of solvents as hydrogen bond donors

Taft and Kamlet's -scale of solvent hydrogen bond donation ability is reexamined with regard to its correlations with three widely used polarity scales: Dimroth and Reichardt's E _T (30), Kosower's Z and Mayer's A _N , as well as with the _m values of the solvents when present as monomeric solutes. The correlation with E _T serves to extend the solvent -scale according to the expression:

Two Algorithms for Computing the Randles–Sevcik Function from Electrochemistry

We derive two expansions of the Randles–Sevcik function : an asymptotic expansion of for x and its Taylor expansion at any x ₀ . These expansions are accompanied by error bounds for the remainder at any order of the approximation.     

Catalytic Mechanism of the “Noncatalytic” Autooxidation of Sulfite

Iron ions are shown to play a special role among transition metal ions in the oxidation of sulfite by oxygen. The thermodynamically favorable formation of chain carriers S : FeOH²⁺+ HSO₃ ^– Fe²⁺+ H₂O + , H _{r 298} ⁰ –250 kJ/mol accompanied by the regeneration of the active Fe(III) form in the reactions of Fe(II) with and HSO₅ ^–provides the efficient catalytic mechanism for sulfite consumption even at [Fe]₀ 10^–8mol/l. Any aqueous solution contains iron ions in this amounts. Thus, the noncatalytic oxidation of sulfite is in fact the catalytic reaction involving unavoidable microadmixtures of iron ions. Other transition metal ions (Mn²⁺, Co²⁺, etc.) can only enhance the catalytic effect of iron admixture.     

ZumHunsdiecker-Abbau von 2-Acylcyclopropancarbonsäuren

2-Acylcyclopropane carboxylic acids (1) are degraded by aHunsdiecker reaction using red HgO/Br₂ to mixtures oftrans- andcis-2-bromo-cyclopropyl alkanones, the former being the major component. The starting materials may be easily prepared by reaction of stabilised S-ylides with ,-unsaturated oxo compounds or -acylvinyltriphenylphosphonium bromides.     

Molecular Structure of 1,2,4,5-Tetracyanobenzene from Gas-Phase Electron Diffraction and Theoretical Calculations

The molecular structure of 1,2,4,5-tetracyanobenzene has been determined by gas-phase electron diffraction and by ab initio calculations at several levels of theory. The electron diffraction study indicates an elongation of the aromatic ring along the (H)CC(H) axis, characterized by angular deformation of the benzene ring and lengthening of the (NC)C—C(CN) bonds. The following bond lengths (r _g) and bond angles were obtained by electron diffraction: .