Fluoroaliphatic esters of fluorosulfonic acid. 6. Interaction of fluorine-containing α,β-bis-fluorosulfatocarbonyl compounds with nucleophilic reagents

Fluorine-containing ,-fluorosulfatocarbonyl compounds interact with halides of alkali metals with the formation of -halogeno--dicarbonyl derivatives.A. N. Nesmeyanov Institute of Heteroorganic Compounds, Russian Academy of Sciences, 177813 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 3, pp. 715–719, March, 1992.     

Application of interactive image analysis to light scattering patterns of some polymer systems

In this paper we describe a system for interactive picture analysis useful for extraction of various types of physical information from both real- and Fourier-space images. The possibility of hardware and software operations are illustrated, with examples of applications such as analysis of light scattering patterns from phase separated systems, semicrystalline polymer films with significant supermolecular morphology and from less regular polymer systems with a pronounced speckle effect. The analysis concentrates on both spatial and time dependent scattering processes and measurements of intensity correlation of scattered light. Although the present examples of application are limited to light scattering patterns of polymer systems, the technique of interactive picture analysis is useful for quantitative extraction of information from real-and Fourierspace images of arbitrary structure.     

Investigation of the metal binding site in methionine aminopeptidase by density functional theory

All methionine aminopeptidases exhibit the same conserved metal binding site. The structure of this site with either Co²⁺ions or Zn²⁺ions was investigated using density functional theory. The calculations showed that the structure of the site was not influenced by the identity of the metal ions. This was the case for both of the systems studied; one based on the X-ray structure of the human methionine aminopeptidase type 2 (hMetAP-2) and the other based on the X-ray structure of the E. colimethionine aminopeptidase type 1 (eMetAP-1). Another important structural issue is the identity of the bridging oxygen, which is part of either a water molecule or a hydroxide ion. Within the site of hMetAP-2 the results strongly indicate that a hydroxide ion bridges the metal ions. By contrast, the nature of the oxygen bridging the metal ions within the metal binding site of eMetAP-1 cannot be determined based on the results here, due to the similar structural results obtained with a bridging water molecule and a bridging hydroxide ion.     

Synthesis and thermal decomposition of 3-aroyl-4-aryl-2-pyrazolines

Summary 3-Aroyl-4-aryl-2-pyrazolines (21–40) have been synthesized by the reaction of ,-unsaturated ketones (1–20) with diazomethane. These 2-pyrazolines gave -methyl-,-unsaturated ketones (41–46) on thermal denitrogenation.Dedicated to Prof. Dr.F. Sauter on the occasion of his 65^th birthday     

An investigation of 3μm reverse-phase octadecylsilane packing materials for high-performance liquid chromatography

Summary The efficiency of high-performance liquid chromatography columns packed with 5 m and 3 m reverse-phase octadecylsilane packing materials has been evaluated using four test mixtures. Both stopped flow and valve injection have been used and typical efficiencies are given.     

Chemical applications of group theory and topology

The following procedure is described for investigating the qualitative dynamics of simple chemical systems: 1) A so-called influence diagram is generated representing the relationships between the reference reactants (phase-determining intermediates); 2) This influence diagram is used to generate a truth table indicating possible transitions between state vectors representing the signs of the time derivatives of of the reference reactant concentrations; 3) The truth table is used to determine a state transition diagram representing the flow topology around unstable equilibrium points; 4) The characteristic equation of the adjacency matrix of the influence diagram is solved in order to determine the presence of such unstable equilibrium points. The two types of qualitative dynamics possible for chemical systems containing two reference reactants and one feedback circuit are bifurcation between two attracting regions (bistability) and limit cycle oscillation. However, in two reference reactant systems oscillation requires an additional self-activating loop to generate the unstable equilibrium point required for its realization. Bistability and limit cycle oscillation are also two of the possible types of qualitative dynamics for chemical systems containing three reference reactants. However, chemical systems with three reference reactants and two or more feedback circuits can also contain interlocking limit cycles, which can lead to toroidal oscillations or chaos. The influence diagrams are given for the systems exhibiting these various types of dynamic behavior along with a summary of the important properties of all 729 possible influences for simple chemical systems containing three reference reactants.     

Improvement of Solubility and Dissolution of 19-Norprogesterone via Inclusion Complexation

In an effort to modify the solubility and dissolution rate of the contraceptive steroid, 19-norprogesterone in order to improve its bioavailability, the cyclodextrin complexation approach was chosen. In solution, the complex formation with -cyclodextrin (-CD), hydroxyethyl -cyclodextrin (HE--CD) and hydroxypropyl -cyclodextrin (HP--CD) was confirmed by using solubility, UV, IR and ¹H-NMR spectrophotometric techniques. The phase solubility diagrams were categorized as A_L-type. The complexing affinity of the CDs investigated were ranked as follows: -CD > HP--CD > HE--CD. The complexation thermodynamic parameters were obtained from the temperature dependence of the dissociation constants. In the solid state, differential scanning calorimetery (DSC) and optical microscopy methods were utilized to characterize the complexes. Dissolution studies showed that such molecularly encapsulated forms offered a marked improvement in the dissolution rate compared to the parent drug.     

‘Hairdressing’ Shish-kebabs by melting

Summary A previous paper established the principle of hairdressing showing that polyethylene shish-kebab fibres can be reversibly transformed by appropriate preparation conditions between three morphologies, smooth fibres; fibres with closely spaced lamellar overgrowths; fibres with widely spaced lamellar overgrowths, where the spacing is sensitively affected by storage temperature (3). In the present paper this hairdressing work is extended to include the molten state. Three classes of morphology analogous to the three obtained from solution (although with certain minor differences) can be obtained by melting shish-kebabs at constant length, followed by quenching or isothermal crystallization. These melt-hairdressed fibres can be transformed back into shish-kebabs of typical solvent hairdressed appearance by the previously established procedures for solvent hairdressing. Thus all these works, following on from the trend established by Pennings (4), serve to highlight the fact thatall shish-kebabs acquire their external morphology at temperatures which are beneath those of the core formation during final cooling or storage and thatall external forms associated with a given core are interconvertible. On the molecular level these features highlight the intrinsically hairy nature of the core fibre as formed.With 5 figures     

Phosphorescence of lyophilized complexes between cyclodextrins andβ-arylpropiophenones

-Arylpropiophenones do not phosphoresce in homogeneous solution as a result of excited state quenching by the -aryl group. In the presence of cyclodextrins the parent substrate, -phenylpropiophenone, shows readily detectable phosphorescence. The complexes show strong phosphorescence after lyophilization to dryness. The phosphorescence intensity of ring-substituted derivatives is strongly dependent upon molecular size and cavity dimensions, suggesting that the -arylpropiophenones can be used to probe these properties.Issued as NRCC-23907     

Chemical Composition of Certain Sedum Species of Kazakhstan

The chemical composition of sevenSedumspecies growing in Kazakhstan was studied by chromatography. The contents of seven groups of natural compounds were determined. Comparison with markers and literature data identified 24 compounds including 9 that have not been described previously inSedumspecies     

α-Alkoxy-β-dicarbonylverbindungen durch Acylierung von Lithiumenolaten

A series of -alkoxy--dicarbonyl compounds2 were prepared by acylation of lithium enolates in good to excellent yields by a simple one-pot procedure.

     

Charge-transfer complexes betweenp-toluidine and iodine in solution: A kinetic study

The kinetics of charge-transfer interaction betweenp-toluidine and iodine in methylene chloride was investigated in depth. Thethermal process of formation of theinner complex was found to proceed to an equilibrium. Thephotochemical process follows a different reaction coordinate, going through the formation of an exciplex between the excitedouter complex and the amine ground state. In both cases the same ionic complex (Am ₂I⁺I ₃ ^– , whereAm stands forp-toluidine) was detected as the final product.

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Kinetische Untersuchung der Charge-Transfer-Komplexe zwischenp-Toluidin und Jod

Zusammenfassung Die Kinetik der Charge-Transfer-Wechselwirkung zwischenp-Toluidin und Jod in Methylenchlorid wurde ausführlich untersucht. Derthermische Prozeß, der zur Bildung desinner-Komplexes führt, geht bis zu einem Gleichgewicht. Derphotochemische Prozeß folgt einer unterschiedlichen Reaktionskoordinate und verläuft über die Bildung eines Exziplexes zwischen dem angeregtenouter-Komplex und dem Amin im Grundzustand. In beiden Fällen wurde derselbe ionische Komplex (Am ₂I⁺I ₃ ^– , wobeiAm fürp-Toluidin steht) als Endprodukt festgestellt.

     

A new detection method for purines in thin-layer chromatography

Summary The separation of some purines by thin-layer chromatography, utilizing precoated plates with Silicagel R as stationary phase and the following mobile phases: i-butanol: methylethylketone: ammonium hydroxide 25%: water (40252015) and n-propanol: ammonium hydroxide 25%: water (80155) is reported.Visualisation of the spots has been achieved by spraying with aqueous 1% uranyl acetate and irradiating with UV both at 254 and 366 nm. The visual detection of a spot was 0.01 g.     

Novel Synthesis of 2β,3β,20β-Triacetoxy-5 -pregnan-6-one

Pregnenolone (2) is used in a novel synthesis of 2,3,20-triacetoxy-6-ketosteroid (6), a key intermediate in the preparation of 20-hydroxyecdysone (1)     

Reactions of dodecacarbonyltriruthenium with α,β-unsaturated ketones. Crystal and molecular structures of two reaction products

The thermal reactions of Ru₃(CO)₁₂ with RCOCH=CHPh (R=Me, p-MeC₆H₄) in hydrocarbon solvents lead to the formation of a series of complexes, several of which have been isolated as individual compounds by chromatography. The dinuclear complex Ru₂(-H)(CO)₆(-MeCOCH=CPh) and the tetranuclear complex Ru₄(-H)(-CO)(CO)₇(p-MeC ₆H₄ COCH=CPh)(-p-MeC₆H₄COCH=CPh)(₄-p-MeC₆H₃COCH=CHPh) are characterized by an X-ray structural study. The structures of other reaction products are discussed on the basis of spectral data. The reactions are accompanied by reduction of the starting enones to the corresponding unsaturated ketones.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1285–1293, July, 1993.     

Comments on the electronic properties of cyclopropane,cyclobutane, and cyclohexane

Spectral quantities of cyclopropane, cyclobutane, cyclohexane, and of several derivatives, have been calculated by a semiempirical all-valence electron SCF-CI MO method. In cyclopropane, HOMO is practically localized in the carbon-frame, and LVMO is purely so. In cyclobutane, these two MO's are based on C-H bonds, while cyclohexane holds an intermediate position. Despite the overall similarity-experimental and computed-of the spectra of these molecules, assignments are non-parallel. Like cyclopropane, cyclobutane can extend conjugation, but to a diminished degree; cyclohexane behaves in this respect like an acyclic alkane. An interpretation of this gradation, in terms of the nature of high-lying MO's, is proposed.     

Formulation and Preliminary in vivo Testing of Rufloxacin-Cyclodextrin Ophthalmic Solutions

Aim of the present work was to investigate the effect of somecyclodextrins (CDs) on the solubility and ocular bioavailability of rufloxacin base (RUF), with theultimate goal of developing an ophthalmic formulation. Phase solubility studies of RUF inpH 7.4 buffer were carried out in the presence of -cyclodextrin (-CD),hydroxypropyl--cyclodextrin (HP--CD) and -cyclodextrin(-CD). The effect of hydroxypropyl methylcellulose (HPMC) on RUF solubility was evaluated after heating the solutionscontaining HP--CD at 120 °C.A significant enhancement of RUF solubility was achieved by associatingthe drug with CDs, particularly HP--CD. This CD formed with RUF a less stablecomplex than that formed by -CD, but did not suffer the solubility limitations ofthe parent CD, and showed a higher solubilizing capacity than -CD. Addition of 0.25%(w/v) HPMC to solutions containing HP--CD increased the solubilizing effect of this CD,thus allowing reduction of the amount necessary for solubilization of 0.3% (w/v) RUF.Preliminary pharmacokinetic data in rabbits indicated that theocular bioavailability of 0.3% (w/v) RUF solubilized by HP--CD was higher when compared witha 0.3% (w/v) RUF suspension used as reference.     

Organization of nanoscale objects via polymer demixing

We present an extremely versatile method for the lateral organization of nano-scale objects (NOs) based on the phenomenon of polymer demixing. NOs are suspended in a solution of two immiscible polymers, which is used to form a thin polymer film by spin coating. During spin coating the two polymers separate to give a microphase structure, whose length scale depends on the experimental conditions. The NOs spontaneously partition into one or other of the polymer phases resulting in their lateral organization. In this work, the organization of CdSe nanoparticles and fluorescent organic dyes was studied by fluorescence microscopy. The NOs were organized in the polymer film in stochastic patterns or in ordered designs on substrates pre-patterned by soft-lithography techniques. Single-particle measurements, using confocal microscopy, showed that at low concentrations there was little aggregation of the particles.     

Screened potential in π-electron systems and its application to the estimation of excitation energies

A diagrammatic technique was developed for the estimation of the screened potential of -electron systems. The screened potential was expanded in terms of the polarization propagators which were constructed from either the singlet, , or triplet vertex part, . These vertex parts correspond to the singlet or triplet excitations, respectively, in the Random Phase Approximation (RPA) containing exchange diagrams. The excitation energies were calculated by using the screened potential in the framework of RPA with exchange. The excitation energies of several conjugated molecules with or without a hetero atom are in agreement with the experimental data.     

Diastereoselectivity in theLewis acid mediated aldol reaction of chiral α, β-epoxyaldehydes with a ketene silyl acetal

Summary The Lewis acid mediated aldol reaction of chiral , -cis andtrans epoxyaldehydes1 and2 withtert-butyl ketene silyl acetal proceeds mainly withanti diastereofacial preference. The best results were obtained forcis epoxyaldehyde1 in the presence of catalytic amounts of BiCl₃·1.5 eq. ZnI₂ (anti:syn 13:1), whereas the poorest stereoselectivity was observed when an excess of LiClO₄ was used (anti:syn 1:1). The more stable epoxyaldehyde conformers were determined and the diastereofacial preference was found to be in agreement with a nucleophilic attack on the energetically more favoured conformers.

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Diastereoselektivität derLewis-Säure-katalysierten Aldolreaction zwischen chiralen , -Epoxyaldehyden und einem Ketensilylacetal

Zusammenfassung DieLewis-Säure-katalysierte Aldolreaktion der chiralen , -cis- und -trans-Epoxyaldehyde1 und2 mittert-Butylketensilylacetal verläuft stereoselektivanti. Die besten Ergebnisse wurden für dencis-Epoxyaldehyd1 in Gegenwart katalytischer Mengen BiCl3·1.5 eq. Znl₂ erhalten (anti:syn 13:1). Die geringste Stereoselektivität trat auf, wenn LiClO₄ im Überschuß eingesetzt wurde (anti:syn 1:1). Das beobachtete Verhalten steht mit einem nucleophilen Angriff am energetisch günstigeren Konformeren im Einklang.