peri-Naphthylenediamines 18. 1,8-Bis(dimethylamino)-4-vinylnaphthalene

The 1-[1,8-bis(dimethylamino)-4-naphthyl[ethyl carbocation generated from the corresponding alcohol in benzene in the presence of Al₂O₃ undergoes elimination according to theE1 mechanism to give previously unknown 1,8-bis(dimethylami no)-4-vinyl naphthalene in a good yield. This compound was also synthesized from 1,8-bis(dimethylamino)-4-formylnaphthalene by the Wittig reaction. Polymerization of the vinylic derivative obtained was studied.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2297–2300, September, 1996.     

On the use of pseudopotentials in molecular calculations

A series of tests was performed of the Kahn-Goddard-Melius-Topiol pseudopotentials in view of their utilization with small contracted basis sets in molecular computations. The effects of inner-shell separability and of basis set contraction are underlined. The utilizability of Topiol's valence least-squares fitted Gaussian basis sets is studied.     

Systematic survey on crystalline features of algal celluloses

Algal cellulose from different origins has been analysed with special reference to the crystalline features, such as allomorphism (I/I or triclinic/monoclinic two- phase model), dimension and uniplanar orientation behaviour of the specific crystallographic plane to the cell wall surface. Three types of cellulose were identified in the algal system: I-rich/broad microfibril/0.6 nm-oriented type; I- dominant/flat-ribbon/0.53 nm-oriented type; and I- dominant/small/random-oriented type. The first type appears to occur in more primitive organisms than the other types. The three types of algal cellulose correlate well with the arrangements of cellulose synthesizing complexes, i.e. multiple-row linear type, consolidated rosette type, and isolated rosette type, respectively. In Chara two types of crystals were found: an I-dominant/ribbon shaped/0.6 nm-oriented type and an I/narrow/random-oriented type. The former type, known to occur in some families of tunicates, was first identified in algal cellulose during this study. Reducing-end staining was successfully applied to microcrystal cellulose samples of Cladophorales and Zygnematales, showing that the cellulose microfibril has a parallel-chain structure for both cellulose I and cellulose I     

Complexation of Oleuropein and trans-Cinnamic Acid with Cyclodextrins

The complexation of oleuropein and trans-cinnamic acid with -, -, and -cyclodextrin has been studied in aqueous model systems by light scaterring. The influence of various parameters (pH, concentration, reaction time, nature of cyclodextrin) has been thoroughly examined. The formation of binary (1:1) inclusion complexes and the higher inclusion ability of -CD for both compounds has been indicated. Trans-cinnamic acid was extracted from olive olive oil following its complexation with -CD at satisfactory recovery levels.     

Synthese von Phosphonoäpfelsäureestern durch Reduktion von 3-Phosphonopyruvaten

Summary The reduction of 3-phosphonopyruvates with ammonia-borane complex proceeds with a very high diastereoselectivity (25:1).Syn- andanti-diastereoisomeric hydroxy esters could be unambiguously assigned by NMR spectroscopy. Furthermore, other -ketophosphonates could easily be reduced. Thus, diethyl-3,3-diethoxy-2-hydroxybutyl phosphonate was obtained which gave diethyl-2-hydroxy-3-oxobutyl phosphonate after hydrolysis the first known phosphonoacyloine.

Herrn Prof.W. Fleischhacker, Wien, mit den besten Wünschen zum 65. Geburtstag gewidmet.     

Synthesis ofN-alkylamides of 3-fluoroalkylaziridine-2-carboxylic acids

The N-alkylamides of 3-fluoroalkylaziridine-2-carboxylic acids have been prepared for the first time by the interaction of ethyl 0-fltioroalkyl-,-dibromocarboxylates with primary amines.Prepared by a known procedure;² characteristics of previously unknown ester1b are given in the Experimental section.     

Pyrazolopyrimidines Based on 5-Aminopyrazoles Unsubstituted at the Position 1

By condensation of various symmetric -diketones with a series of 5-aminopyrazoles that are unsubstituted at the position 1, we have obtained a series of pyrazolo[1,5-a]pyrimidines that are of interest as physiologically active compounds. Hexafluoroacetylacetone reacts in another direction, forming pyrazolo[4,5-b]pyridine.     

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.

     

Band structure of nonclassical polymers

It is shown that fully conjugated alternant nonclassical polymers are comparatively stable systems as a result of the considerable delocalisation energy.The energy characteristics of the polymers are strongly determined by the electron spin distribution of the degenerate nonbonding molecular orbitals; the full spin configuration,S>0, is favoured. The spin densities depend on the electron correlation and alternate; this corresponds to a ferrimagnetic state of the polymer at 0°K.     

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.     

In vitro Release Study of Tretinoin from Tretinoin/Cyclodextrin Derivative Complexes

The effects of -cyclodextrin, hydroxypropyl -cyclodextrin and dimethyl -cyclodextrin complexes on the in vitro release of tretinoin gels were investigated. The experiments were carried out in a Franz cell using a silicone membrane as a barrier for the diffusion of the vehicle. Two types of vehicle were compared: a hydroalcoholic gel in which both tretinoin and the inclusion complexes are soluble, and an aqueous gel in which only the complexes are soluble but tretinoin is dispersed. As expected, the release rate of free tretinoin in the hydroalcoholic gel is much faster than in the aqueous gel. However, with the aqueous gel, the cyclodextrin complexation enhances the diffusion rate of the active drug through the membrane, especially with the hydroxypropyl cyclodextrin inclusion compound. The release of tretinoin is related not only to the stability constant of the inclusion, but also to the binding properties of the inclusion compounds to the vehicle.     

Acidity scale for strong Bronsted acids referred to their complexes with water and in the Gaseous phase

CNDO/2 calculations on AH...B complexes in the gaseous phase (AH = strong acids, B = water) gives the following order H₂O < HF < HCl < HSO₃CF₃ < H₂SO₄ < HSO₃F < HClO₄ < H₃O⁺ if we take as reference the Wiberg residual indexp(H... O). Other properties and in particular the charge transfer behave in the same fashion. Charge variations for each atom give an explanation for the Pauling rule for the oxygenated acids.

     

A kinetic method for the direct determination of cellobiose hydrolysis by β-glucosidases

TheSomogyi—Nelson colorimetric method is applied in a new manner which is more suitable for following the kinetics of cellobiose hydrolysis catalyzed by -glucosidase (EC 3.2.1.21). TheSomogyi—Nelson colour reagent, which is a mixture of the solutions of the reagent ofSomogyi and that ofNelson in a volume ratio of 1:1, is added to the enzyme-substrate solution at the very start of the reaction. The colour reagent reacts with the product (D-glucose). Under the reaction conditions (0.1M acetate buffer,pH = 5.0 and temperature 37°C) the colour reagent does not affect the enzyme activity. The method excludes any inhibition of the product, owing to the continuous removal of the latter by the colour reagent. The method suggested has been applied to monitor cellobiose hydrolysis with -glucosidase, contained in four cellulase enzyme preparations from various fungal sources. The values of theMichaelis parameters (Km, V) were determined.

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Eine kinetische Methode zur Verfolgung der Hydrolyse von Cellobiose durch ß-Glucosidasen

Zusammenfassung Die kolorimetrische Methode nachSomogyi undNelson wird nach einem neuen Verfahren zur Verfolgung der Kinetik der hydrolytischen Spaltung von Cellobiose, katalysiert durch -Glucosidase (EC 3.2.1.21), angewandt. Das Farbreagenz nachSomogyi undNelson (Mischung der Reagenzien vonSomogyi undNelson im Volumenverhältnis 1:1) wird der Enzym-Substrat-Lösung zu Beginn der Reaktion hinzugefügt. Das Farbreagenz tritt mit derD-Glukose in Reaktion, wobei unter den gegebenen Reaktionsbedingungen (0,1M Azetatpuffer,pH = 5,0 und 37°C) die Enzymaktivität nicht beeinflußt wird. Die entwickelte Methode wurde zur Verfolgung der Hydrolyse von Cellobiose durch ß-Glucosidasen, die in vier Enzympräparaten aus verschiedenen Pilzstämmen enthalten waren, angewandt. Es wurden dieMichaelis-Parameter (Km, V) bestimmt.

     

Effect of Cyclodextrins on the Chemical Stability of ST1435, a Contraceptive Steroid Progestin, in Aqueous Solution

The influence of cyclodextrins (CDs) on the chemical stability of the contraceptive steroid progestin, ST1435, in aqueous solution has been studied using reversed phase high performance liquid chromatography. The effects of CD structure, temperature, and CD concentration on the rate of degradation were investigated. It was found that the drug degraded to different extents following a pseudo-first order reaction mechanism. The presence of the host molecules affected the degradation rate as a result of complexation which might result in protection of the labile moiety of the drug molecule against degradation. Hydroxypropyl--cyclodextrin (HP--CD) and hydroxyethyl--cyclodextrin (HE--CD) retarded the degradation in contrast to -cyclodextrin (-CD) which accelerated the steroid degradation. The stabilizing action of HP--CD is larger than that of HE--CD. The degradation rate increased upon increasing temperature and the Arrhenius equation is valid. Lineweaver-Burk equation analysis indicated that the steroid included inside the CD cavity degraded three times more slowly than did the free ST1435 in solution. This equation further supported the formation of a 1 : 1 inclusion complex between ST1435 and HP--CD with a stability constant of 934.5 M-1 at 65°C.     

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.     

Die Acetalgruppe, 1. Mitt. Acetale von Halogenmethyl-arylcarbinolen

Several halomethyl-arylcarbinols were prepared, and the influence of substituents on enantiomer selectivity in the acetalisation reaction with [2S-(2,3a,4,7,7a)]-octahydro-7,8,8-trimethyl-4,7-methanobenzofuran-2-ol was examined.

Unserem sehr verehrten Lehrer, Herrn Prof. Dr.Otto Hromatka, mit den besten Wünschen zum 80. Geburtstag gewidmet.     

Reactions of excited fullerenes C60 and C70 studied by mass spectrometry

The transformation of the mass spectra of the laser-desorbed C₆₀ and C₇₀ samples with a successive increase in the laser power, resulting in an increase in the degree of excitation of C₆₀ (C₇₀) and in the number of the particles in the laser plume, was studied. Unusual metastable clusters (C₆₀ + C₂) and (C₇₀ + C₂) are formed even at a minimum laser power and begin to dissociate after 0.5 s following a short (3 ns) laser pulse. An increase in the laser power results in the appearance of peaks of metastable clusters C₆₂ (C₇₂) with the statistically normal lifetime without a delay of dissociation. A further increase in the laser power produces metastable clusters C_60k–2n and C_70k–2n (k = 2, 3) formed without a lag from the dimers and trimers of C₆₀ (C₇₀) by the ejection of a number of C₂ required for the stabilization of the C₂ molecules. The peak of C₇₀ appears simultaneously with the appearance of the (C₆₀)_2–2n peaks upon the laser desorption of pure C₆₀. These findings provide evidence for the growth of the excited fullerene clusters by coalescence and subsequent stabilization due to the ejection of a small fragment rather than by the implantation of C₂ into the fullerene framework. This mechanism of cluster growth should be taken into consideration in modeling fullerene formation in an electric arc reactor, because the clusters formed under these conditions have a substantial excess internal energy.     

Spectroscopic and quantum chemical investigation of enol-enol tautomerism of 2-acetyltetronic acid

Vibratonal spectra of 2-acetyltetronic acid (ATA) (3-acetyloxolane-2,4-dione) were investigated in different aggregate states.Ab initio quantum chemical calculations (3-21G basis set) of 2-formyltetronic acid as analogue of ATA and semi empirical calculation of ATA were carried out. The tautomeric forms of ATA can be arranged in the following series with respect to thermodynamic stability (in decresing order):1a,1b,2a,2b.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1043–1048, June, 1995.     

Novel techniques for plasma diagnostics: Electron paramagnetic resonance and laser-induced fluorescence spectroscopy

Diagnostic techniques for low-pressure, cold plasmas have mostly been limited to emission and mass spectrometry. Herein, the techniques of gas-phase electron paramagnetic resonance and laser-induced fluorescence spectroscopy are briefly reviewed. Particular attention is paid to their attributes which make them good candidates for plasma diagnostic tools. It is found that gas-phase electron paramagnetic resonance can be used to determine and monitor the absolute concentration of a number of important plasma species, e.g., free radicals and atoms. Laser-induced fluorescence can also monitor, with even more sensitivity, but perhaps not so well absolutely, the concentrations of many plasma species, e.g., free radicals, metastable excited states, and molecular ions.