Structural and dielectric investigations of a binary system of a bi-swallow-tailed and a terminally-polar compound

Induced smectic A phases in binary mixtures of a bi-swallow-tailed component and a second component are described as 'filled smectic A phases', since the second rod-like component is considered to occupy spaces between the terminal branches of the bi-swallow-tailed molecules. A new system of this kind is now described where the second rod-like component has a terminal dipole, thereby enabling dielectric studies of the mixtures. These measurements coupled with calorimetric and X-ray measurements give information about the packing and dynamics of the mixed phases.     

Synthesis of a tetraazacyclotetradecadiene and a pentaazacyclotetradecatriene

Useful procedures for preparing a novel tetraazacyclotetradecadiene and a pentaazacyclotetradecatriene are reported. J. Heterocyclic Chem., 14, 1097 (1977)     

Formation of a tris-capsule and a tris-carceplex from a cyclic six-bowl assembly

A macrocycle composed of six cavitands was assembled into a tris-capsule and a tris-carceplex, each of which encapsulates three guest molecules.     

On a unified treatment of kinetics and diffusion,and a connection to a nonlocal boltzmann equation

Fick's law of diffusion has been generalized to include kinetic processes, the transport term of the Boltzmann equation, and nonlocal interaction processes. It is shown that the collision interaction term can be obtained by the introduction of a quantum stochastic potential equation. Some approximations of a nonlocal Boltzmann equation can be solved exactly. The solutions can be applied to problems of molecular pattern in biology.     

Synthesis,Properties and Reactivity Studies of a Hetero-dicopper Complex Consisting of a Porphyrin and a Bispyridylamine Moiety Connected by a Xanthene Backbone

Synthesis, characterization and reactivity studies of a hetero-dicopper complex, particularly towards oxygen reduction are presented. A bischlorido copper(II) trishistidine-type coordination unit is positioned directly above a copper porphyrin unit. The close distance between the two coordination fragments is secured by a rigid xanthene backbone. Surprisingly, the dinuclear complex is not active towards oxygen reduction unlike the earlier published mononuclear analogues with a bispyridylamine copper center. However, the compound architecture of this multinuclear metal complex is interesting and can play an important role in the development of new catalysts for ORR.     

Synthesis of (+)-uniflorine a: a structural reassignment and a configurational assignment

The total synthesis of (+)-uniflorine A has allowed for the structural reassignment and the configurational assignment of the alkaloid (-)-uniflorine A from a 1,2,6,7,8-pentahydroxyindolizidine structure to (-)-(1 R,2 R,3 R,6 R,7 S,7a R)-1,2,6,7-tetrahydroxy-3-hydroxymethylpyrrolizidine (6- epi-casuarine).     

Total Syntheses of a 16a'-Homoleurosidine and a 16a'-Homovinblastine

Vinblastine has been used in clinic as an anti-cancer agent. Due to its high cytotoxity, generation of vinblastine congeners as safe anti-cancer agents is always the interesting topic in medicinal chemistry. In the previous synthesis of vinblastine, it has been found that a higher energy conformation of vinblastine lacking cytotoxity and inhibition against tubulin polymerization, can be converted to its lower energy natural conformation on heating to 110 ℃. The high temperature (110 ℃) other than a physiological temperature required for the conformational inversion excludes the possibility of using the higher energy conformational isomer as a potential pro-drug for thermal activation. In the continuing of searching for thermal activated anti-cancer pro-drug, we re-designed and synthesized new vinblastine congeners with the enlarged azonine ring by inserting one carbon atom at the C-16 position of azonine ring in order to decrease the energy barrier for the conformational inversion.In this paper, we wish to report the total syntheses of 16a'-homoleurosidine and 16a'-homovinblastine, the azonine ring expanded compounds of vinblastine and leurosidine respectively. The synthesis of 16a'-homoleurosidine was achieved through enatioselective generation of a tetracyclic intermediate by a Diels-Alder reaction, followed by ring expansion of the tetracyclic intermediate by regioselective rapture of a cyclopropane ring as key steps. The synthesis of 16a'-homovinblastine was achieved through stereoselective inversion of the tertiary hydroxyl group from R configuration to the S configuration in the tetracyclic intermediate. The 16a'-homoleurosidine was obtained dominantly in its high energy conformation at room temperature and neutral condition. On protonation, a 1:1 mixture of atropisomers of 16a'-homoleurosidine was found. In contrast to 16a'-homoleurosidine, the 16a'-homovinblastine existed in the form of two atropisomers in a 1:2.3 ratio at room temperature and neutral condition, with a complete shift to the lower energy atropisomer with increasing solvent acidity. The hydrogen bond formed between the nitrogen atom and the hydroxyl group of piperidine ring played a key role in controlling the equilibrium shift between the higher energy atropisomer and the lower energy atropisomer.     

Analytical investigation and numerical modeling of collisions between a droplet and a fiber

The kinetics of the collisions between droplet and the fiber is being studied in both theoretical and numerical way. During theoretical investigations the balances between the various components of total energy of the droplet have been used. As a result, we have obtained the conditions (expressed in terms of non-dimensional parameters characterizing the system) at which the deposition of the droplet on the fiber or the separation of the droplet from the fiber occurs. The results of theoretical computation have been compared with the results of the numerical simulations using the two-color lattice-Boltzmann method.     

Control of mesoporous silica nanostructures and pore-architectures using a thickener and a gelator

A chiral cationic thickener l-ValPyBr, which was able to enhance the viscosity of water and form loosely physical gel in mixtures of water and alcohols, was synthesized. Sol-gel polymerization of TEOS was carried out in mixtures of water and alcohols under basic conditions using the self-assemblies of l-ValPyBr as template. The left-handed twisted mesoporous silica nanoribbons, which were constructed by nanotubes in monolayer, were obtained, and they tended to self-assemble into bundle structure. Stirring under the preparation process played an important role in the formation of this bundle structure. The obtained silica nanoribbons were uniform in width, thickness, and helical pitch without combining amorphous particles. The helical pitch and pore size of the mesoporous silica nanoribbons sensitively depended on the volume ratio of alcohols to water in the reaction mixtures. With increasing volume ratio of alcohols to water in the reaction mixture, the morphologies of the obtained silica changed from left-handed twisted ribbon to coiled ribbon, then to tubular structure. A compound l-ValPyPF6, structurally related to thickener l-ValPyBr, was able to form physical gel in ethanol, THF, acetonitrile, and the mixtures of ethanol and water. Left-handed multiple helical mesoporous silica nanofibers were prepared by using the self-assemblies of l-ValPyPF6 as template in mixtures of water and alcohols under basic conditions. By controlling both the volume ratio of ethanol to water and the weight ratio of l-ValPyPF6 to TEOS, two- or three-dimensional pore-architecture constructed by porous chiral nanotubes was obtained.     

Coimmobilization of a redox enzyme and a cofactor regeneration system

The coimmobilization of nitrobenzene nitroreductase and glucose-6-phosphate dehydrogenase in silica particles enables the continuous conversion of nitrobenzene to hydroxylaminobenzene with NADPH recycling.     

Taming Mars with a tent and a tunnel: creation of a biosphere-city

An unconventional site-specific outdoor utility sculpture, used as a Strait of Gibraltar stopper, may soon store unwanted Earth-atmosphere derived wastes (mineralized CO2 and CFCs) for hundreds of years. Such a Land Art processing facility, an anti-global warming/cooling antidote, is an appropriate macro-engineering response to allegedly impending human survival macro-problems.     

Cation-pi interactions of a thiocarbonyl group and a carbonyl group with a pyridinium nucleus

Attractive interactions between a thiocarbonyl group and a pyridinium nucleus, and between a carbonyl group and a pyridinium nucleus have been proven by (1)H and (13)C NMR studies, UV-vis spectral analyses, and X-ray crystallographic analyses of nicotinic amides 1 and 3, and pyridinium salts 2 and 4. Comparison of the Deltadelta values, which are the differences in the chemical shifts with reference compounds 5 or 6, showed that the absolute Deltadelta values of 2 and 4 are much larger than those of 1 and 3. In the UV-vis spectra, the n-->pi absorption of the C=S group of 2a exhibited a significant blue shift in CHCl(3). X-ray crystallographic analysis of 1-4 clearly showed that the C=S group of 2a and the C=O group of 4 are very close to the pyridinium moiety compared to the case of 1 and 3. In addition, the X-ray crystal packing structure of 2a showed the C=S group is sandwiched between two pyridinium rings. These experimental results strongly suggested the existence of attractive (C=S)...Py(+) and (C=O)...Py(+) interactions in solution and in crystal. The optimized geometries of 1 and 2 calculated at the HF/6-311G level are in good agreement with their X-ray geometries. MP2/6-311G calculations for the model systems of pyridinium salts 2 and 4 predicted that the electrostatic and induction energies are the major source of the attractive interactions. Since the larger contribution of electrostatic and induction interactions are characteristic features of cation-pi interactions, the (C=S)...Py(+) and (C=O)...Py(+) interactions would be classified as a cation-pi interaction.     

Unprecedented conversion of triethylamine and disulfur dichloride into a thienopentathiepin and a heptathiocane

[reaction: see text] In a remarkable cascade reaction, triethylamine is converted into the thienopentathiepin 2a and the heptathiocane 3a by a preequilibrated solution of disulfur dichloride and DABCO in chloroform.     

Structure and Properties of a Compound Based on a Copper Powder and Polysiloxane

The phase composition, thermal stability, and electrical conductivity of a compound formed by a polymethylsiloxane lacquer and copper were studied in relation to the temperature of formation of a coating on its basis.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 4, 2005, pp. 595-598.Original Russian Text Copyright © 2005 by Shul’pekov, Lyamina, Rybakov, Kirdyashkin, Maksimov.     

Synthesis and biological properties of a tryptophan-containing fragment of a myelin protein and its analogs

Summary 1. By the azide condensation of fragments followed by the hydrogenolysis of the completely protected nonapeptides formed, the encephalitogenic nonapeptides with the structure Phe-Ser-Try-Gly-Ala-Glu-Gly-Gln-Arc and two of its analogs — the 6-glycine and 5,6-diglycine compounds, have been synthesized.2. It has been shown that the 6-glycine analog induces EAE, i.e., the side chain in position 6 is not essential for the appearance of EAE activity.3. The absence of an encephalitogenic effect in the 5,6-diglycine analog permits the conclusion that the side chain of the alanine-5 makes a contribution to the induction of the disease.4. The N-acetyl derivative of the encephalitogenic nonapeptide retains a high EAE activity.Institute of Molecular Biology and Genetics, Academy of Sciences of the Ukrainian SSR, Kiev. A. V. Palladin Institute of Biochemistry, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 507–517, July–August, 1976.