A new method of calculation of the melting temperatures of crystals of Group 1A metal halides and francium metal

A new method of calculation of melting temperatures of binary ionic crystals has been suggested. The method is based on finding a matrix relation between the ionic radii (the lattice energy U) and melting temperature of ionic crystals of the MX type, where M is a Group 1A metal, and X is a halogen. From the equation for the lattice energy U, a new equation has been derived for calculation of the melting temperature of ionic crystals with the use of only the ionic radii and the degree of bond ionicity ?: T _m = f(U, ?). The average error of determination of T _m for alkali-metal halides is 2.80%. The melting temperatures of francium halides and alkali-metal astatides (including FrAt) have been calculated. It has been shown that the accuracy of calculation of the melting temperature of ionic crystals depends on the degree of bond ionicity: the error increases with an increase in the covalent contribution. On the basis of the melting temperatures of metal halide crystals, a method has been developed for the calculation of the melting temperatures of corresponding metals. The melting temperature of francium has been calculated to be 24.861 ± 0.517°C.     

A straightforward synthesis and partial hydrolysis of cysteine-derived 2,5-diketopiperazines

A mild and straightforward preparation of cysteine-derived 2,5-diketopiperazines (DKPs) is reported, by cyclization of (R)-2,2-dimethyltetrahydrothiazole-4-carboxylic acid hydrochloride or of (R)-tetrahydrothiazole-4-carboxylic acid hydrochloride, mediated by HBTU and DIEA. One DKP has been characterized by X-ray analysis, while the other has been hydrolyzed to cyclo-Cys-Cys. The preparation of this latter compound has been previously reported to be troublesome and low yielding.     

Synthetic studies towards dendridine A: synthesis of hemi-dendridine A acetate by Fischer indolization

A short synthesis of hemi-dendridine A acetate has been accomplished. The synthesis is based on a modified Fischer indolization that represents a rare example of the single-step synthesis of a 7-oxytryptamine from an ortho-oxygenated phenylhydrazine. The synthetic route required developing an efficient synthesis of N-acetyl-2-pyrroline, the key coupling partner for the modified Fischer indolization. Some interesting chemistry associated with the abnormal Fischer indolization has been uncovered, whereby two molecules of the phenylhydrazine substrate combined along the abnormal reaction pathway, affording an unusual N-phenylindoleamine product.     

Classification of oxide glasses: A polarizability approach

A classification of binary oxide glasses has been proposed taking into account the values obtained on their refractive index-based oxide ion polarizability α_O2−(n₀), optical basicity Λ(n₀), metallization criterion M(n₀), interaction parameter A(n₀), and ion's effective charges as well as O1s and metal binding energies determined by XPS. Four groups of oxide glasses have been established: glasses formed by two glass-forming acidic oxides; glasses formed by glass-forming acidic oxide and modifier's basic oxide; glasses formed by glass-forming acidic and conditional glass-forming basic oxide; glasses formed by two basic oxides. The role of electronic ion polarizability in chemical bonding of oxide glasses has been also estimated. Good agreement has been found with the previous results concerning classification of simple oxides. The results obtained probably provide good basis for prediction of type of bonding in oxide glasses on the basis of refractive index as well as for prediction of new nonlinear optical materials.     

A study of cetylpyridinium cation sorption on Na-vermiculite

The sorption of cetylpyridinium on Na-vermiculite has been studied by the adsorption, calorimetry, and X-ray diffraction methods. The ion-exchange component of cetylpyridinium sorption on Na-vermiculite has been distinguished and analyzed. Variations in the integral heat of ion exchange of cetylpyridinium cations on Na-vermiculite have been determined as depending on the amount of absorbed cetylpyridinium by the calorimetry method. X-ray diffraction analysis of cetylpyridinium-Na-vermiculite organomineral complexes with different contents of exchange cations has been carried out in parallel. The formation of monolayer (interlayer spacing Δd = 20.25 Å) and bilayer (Δd = 37.27 Å) intercalation structures with a tilt angle of cetylpyridinium ions to the silicate basal surface of ≈57° has been revealed.     

Versicoside — A new lignan glycoside fromHaplophyllum versicolor

A new lignin glyocoside has been isolated fromHaplophyllum versicolor and has been called versicoside. It has been established by chemical and spectral methods that verscioside is (+)-epipinoresinol 4′-O-[O-α-L-rhamnopyranosyl-(1 → 6)-β-D-glucopyranoside].     

A facile two-step chemoenzymatic access to natural germination inhibitor (+)-erigeronic acid A

A facile two-step synthesis of natural germination inhibitor 5-butyl-3-oxo-2,3-dihydrofuran-2-yl-acetic acid [(+)-erigeronic acid A, 1] has been described via highly regioselective ring opening of (R)-acetoxysuccinic anhydride with the primary enolate of butyl methyl ketone, followed by an enzymatic hydrolysis and an in situ dehydrative cyclization pathway with 77% overall yield. On the basis of the present chemoenzymatic approach, (R)-configuration has been assigned to the C-2 chiral centre of the natural erigeronic acid.     

Nivyaside — A new glycoside fromLeucanthemum vulgare

From the ligulate flowers ofLeucanthemum vulgare Lam. growing on the territory of the Georgian SSR a new glycoside has been isolated which has been called nivyaside and has the structure 8-(1-α-D-glucopyranosyl-5-deoxyquercit-5-yl)-4′,5,7-trihydroxyflavone.     

Alkaloids of the flora of Mongolia V. Turpelline — A new alkaloid fromAconitum turczaninowii

In the course of a further study of the alkaloids of the epigeal part of Aconitum turczaninowiia new alkaloid has been isolated, which has been named turpelline. A structure for turpelline has been proposed on the basis of a study of its IR, mass, PMR, ¹³ C NMR, and 2D COSY spectra.     

A practical synthesis of S-quinuclidine-2-carboxylic acid and its enantiomer

A short and convenient synthesis of (S)- and (R)-quinuclidine-2-carboxylic acids has been developed. The resolution of enantiomers has been accomplished by both chemical and enzymic means.     

Phytoecdysteroids of plants of the genusSilene. IV. Sileneoside C — A galactoside of intergristerone A fromSilene brahuica

The phytoecdysteroid sileneoside C has been isolated from the roots ofSilene brahuica Boiss. It has been shown that sileneoside C is intergristerone A 22-0-α-D-galactoside.     

A computational analysis of ordering in 2O.4 based on quantum mechanics and intermolecular forces

A computational analysis of ordering in p-ethoxybenzylidene-p-n-butylaniline (2O.4) has been carried out based on quantum mechanics and intermolecular forces. The evaluation of atomic charges and dipole moments at each atomic center has been carried out using the CNDO/2 method. The configuration energy has been computed using the modified Rayleigh-Schrödinger perturbation method at an interval of 1 Å in translation and 10° in rotations. The various possible geometrical arrangements of molecular pairs during the different modes of interactions have been considered, and the most favorable configuration of pairing has been obtained. A comparative picture of the molecular parameters, such as the total energy, binding energy, and total dipole moment of 2O.4 with other nematogen 4-4′-di-n-propoxy-azoxybenzene (DPAB) and 5-(trans-4-ethylcyclohexyl)-2-(4-cyanophenyl)-pyrimidine (ECCPP), has been given. The results are discussed in the light of experimental and other theoretical observations.     

Stereoselective synthesis of musclides A1, A2 and B

An expedient method for the stereoselective preparation of musclide A1, A2 and B, cardiotonic-potentiating principles from musk, has been achieved. The key step is the addition of the O-benzyl ethers of prop-2-yn-1-ol and (R)-but-3-yn-2-ol to aldehydes mediated by zinc triflate, Et₃N, and (+)- or (−)-N-methylephedrine. In some cases, the partial reduction of the resulting alkynols to Z-olefins has allowed us to remove the minor stereoisomer easily by chromatography to afford highly stereoenriched precursors of musclides.     

A short and efficient synthesis of (R)-(−)-sporochnol A

A short and efficient synthesis of (R)-(−)-sporochnol A in five steps and 9% overall yield has been developed. The sequence uses as starting material the easily available enantiopure monoketal derived from 1,4-cyclohexanedione and (R,R)-hydrobenzoin that serves as a chiral auxiliary.     

Onekotanogenin — A new triterpene genin from the holothurianPsolus fabricii

The structure of onekotanogenin — a new triterpene genin from the holothurianPsolus fabricii — has been established with the aid of¹H and¹³C NMR spectroscopy and a chemical correlation with the previously known cucumariogenin. Its structure has been determined as 20 (S)-acetoxy-3β, 16-dihydroxylanost-7-en-8-oic acid 18,16-lactone. It has been shown that its 25,26-dihydro derivative is the native genin of psolusoside B — a minor glycoside from the holothurianPsolus fabricii Düben et Koren.     

A study of n-dodecylammonium acrylamido-2-methylpropanesulfonate association in aqueous solutions

Association of a micelle-forming monomer, n-dodecylammonium 2-acrylamido-2-methylpropanesulfonate, in aqueous solutions has been studied in a concentration range of 1.5 × 10^?3–2.5 × 10^?1 M with the use of conductometry, capillary and rotational viscometry, isothermal translational diffusion, and atomic force microscopy. Two critical micelle concentrations have been determined, and the shape of n-dodecylammonium 2-acrylamido-2-methylpropanesulfonate micelles has been proposed.     

Micranthoside — A new glycoside fromEupatorium micranthum

From the epigeal parts of the plantEupatorium micranthum Less., introduced into the Sukhumi Botanical Garden, a new glycoside has been isolated which has been called micranthoside and which has the structure of 4′,5-di-0-β-glucosyl-7-0-methyldihydrokaempferol or 4′,5-di-0-β-D-glucosyl-7-0-methylaromadendrin.     

A synthesis of 5-hydroxysedamine using hydroformylation

A synthesis of 5-hydroxysedamine, a Sedum alkaloid, has been completed using N,O-heterocycle chemistry to establish the aminoalcohol structure, hydroformylation to form the piperidine ring and diastereoselective dihydroxylation to introduce the 5-hydroxy group.     

Phytoecdysteroids of plants of the genusSilene. III. Sileneoside A — A new glycosidic ecdysteroid ofSilene brachuica

Ecdysterone (I), viticosterone E, polypodine B, and integristerone A (II) have been isolated from the epigeal part of the plantSilene brachuica Boiss. In addition to substances (I) and (II), the phytoecdysteroid sileneoside A has been isolated from the root of this plant. It has been shown that sileneoside A is ecdysterone 22-O-α-D-galactoside.     

A simple route to β-aminomethylketones

A simple procedure leading to β-aminomethylketones has been developed. The procedure involves base-catalyzed Michael-type addition of sodium t-butyl acetoacetate to N-Boc imines generated in situ followed by hydrolysis and decarboxylation of the adducts.