An asymmetric aminohydroxylation approach to the azepine core of (-)-balanol

[reaction: see text]An efficient formal synthesis of the potent protein kinase C inhibitor (-)-balanol that relies on a modified asymmetric aminohydroxylation of the alpha,beta-unsaturated aryl ester (1) is reported. The aryl ester functionality and the dihydroquinyl alkaloid ligand system (DHQ)2-AQN are used to control the regio- and enantioselectivity of the process.     

Polystyrene-block-poly(ethylene oxide) stars as surface films at the air/water interface

Star diblock copolymers containing polystyrene (PS) and poly(ethylene oxide) (PEO) were investigated as surface films at the air/water interface. Both classic and dendritic-like stars were prepared containing either a PS core and PEO corona or the reverse. The investigated polymers, consisting of systematic variations in architectures and compositions, were spread at the air/water interface, generating reproducible surface pressure-area isotherms. All of the films could be compressed to higher pressures than would be possible for pure PEO. For stars containing 20% or more PEO, three distinct regions appeared. At higher areas, the PEO absorbs in pancakelike structures at the interface with PS globules sitting atop. Upon compression, a pseudoplateau transition region appeared. Both regions strongly depended on PEO composition. The pancake area and the pseudoplateau width and pressure increased in a linear fashion with an increasing amount of PEO. In addition, minimum limits of PEO chain length and mass percentage were determined for observing a pseudoplateau. At small areas, the film proved less compressible, producing a rigid film in which PS dominated. Here, the film area increased with both molecular weight and the amount of PS. Comparison with pure linear PS showed the stars spread more, occupying greater areas. Among the stars, the PEO-core stars were more compact while the PS-core stars spread more. The influence of architecture in terms of the core/corona polymers and branching were also examined. The effects of architecture were subtle, proving less important than PEO chain length or mass percentage.     

Stabilizing effect of anisotropic thermal diffusion on the ablative Rayleigh-Taylor instability

Linear theory of the ablative Rayleigh-Taylor instability in anisotropic diffusive materials is presented. This analysis indicates that enhancing diffusion in a plane transverse to the mean longitudinal flow can strongly reduce the growth of the instability. In the context of inertial confinement fusion, it is shown that anisotropic diffusion can be achieved using a laminated ablator made of successive layers of different diffusive properties. Numerical simulations confirm the theoretical predictions and indeed exhibit a significant stabilization of the ablation front for laminated ablators.     

Etude thermoanalytique et lyodisponibilite de dispersions solides du tolbutamide

We have established the phase diagram tolbutamide (TBM)-PEG 6000 and determined the eutectic composition 1/9 (w/w) in tolbutamide and melting temperature 56.2°C±0.3; no solid solution has been found. Negative mixing enthalpies of physical mixture (?2.5 J·g^?1) and solid dispersions coprecipitate (?3.9 J·g^?1) melt (?9.9 J·g^?1) for eutectic composition involve the existence of interactions between drug and carrier. We have determined the dissolution kinetics: amount % dissolved (10 min) 65.87±0.55 (physical mixture), 78.02±0.02 (coprecipitate), 99.90±0.10 (melt). We have observed a good agreement between dissolution kinetics and mixing enthalpies data.     

Etude thermoanalytique de substances psychotherapeutiques. I. Anxiolytiques. Phenprobamate,meprobamate, clobazam et medazepam

The thermoanalytical study of phenprobamate (a), meprobamate I (b), clobazam (c), medazepam I (d) has enabled the existence of polymorphs for (d) to be established, and to confirm that of (b). The thermal stability and decomposition kinetics of commercial forms of drugs have been determined; their temperatures and intervals of fusion are given. Knowing the thermal behaviour of these compounds, their degree of purity: 99.67±0.19% (a), 99.32± 0.04% (b), 99.61±0.07% (c), 99.66±0.14% (d); their enthalpy, 27.58±0.69 (a), 34.23±1.22 (b), 30.38±0.81 (c), 21.48±0.75 kJ mole^-1; and entropy of fusion have been evaluated by differential scanning calorimetry.     

A general method for the enantioselective synthesis of pantolactone derivatives

An efficient enantioselective synthesis of beta,beta-dialkyl-gamma-substituted pantolactones has been achieved utilizing the cationic [Sc((S,S)-R-pybox)](Cl)(2)(+), R = Ph (9), t-Bu (10), complex in a catalyzed aldol reaction as the key step. The pantolactone derivatives are isolated in high enantiomeric excesses. [reaction: see text]     

Du comportement thermique de la khelline

Résumé Le comportement thermique de la khelline a été étudié par thermomicroscopie, analyse calorimétrique différentielle, analyse thermique différentielle et par mesure de la transparence. Le polymorphisme de ce principe actif a été décelé à l'aide des différentes méthodes; la forme commerciale (I) fondant à 153.3° et la forme (II) à 150.3° ont été identifiées, leurs enthalpies (7725±166 cal·mole^–1, 6668±230 cal·mol^–1), leurs entropies (18.17±0.41, 15.76+0.54) de fusion respectives évaluées, le taux de pureté de la forme (I) déterminé.

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The thermal behaviour of khellin has been studied by thermomicroscopy, differential scanning calorimetry, differential thermal analysis and measurement of transparency. The polymorphism of this drug has been established; the commercial form (I) melting at 153.3° and the form (II) melting at 150.3° have been identified, and their enthalpies (7725±166 cal·mole^–1, 6668±230 cal·Mol^–1) and entropies (18.17±0.41,15.76± 0.54) of fusion evaluated, while the degree of purity of form (I) has been determined.

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Zusammenfassung Das thermische Verhalten von Khellin wurde durch Thermomikroskopie, Differentialkalorimetrie, Differentialthermoanalyse und Transparenzmessung untersucht. Der Polymorphismus dieses Wirkstoffes wurde an Hand der verschiedenen Methoden gezeigt; die handelsübliche Form (I), welche bei 153.3 °C und die Form (II), welche bei 150.3 °C schmilzt, wurden identifiziert, ihre Enthalpien (7725±166 cal·Mol^–1, 6668±230 cal·Mol^–1) ihre Schmelz-Enthropien (18.17±0.41, 15.76±0.54) ermittelt und der Reinheitsgrad der Form (I) bestimmt.

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, , , . , (I), 153.3° (II) — 150.3°. , 7725±166 ·^–1 6668±230 · ^–1, 18.17±0.41 15.76±0.54. (I).

     

The relaxation time spectrum of nearly monodisperse polybutadiene melts

The relaxation behavior of polymers with long linear flexible chains of uniform length has been investigated by means of dynamic mechanical analysis. The relaxation time spectrum (H()) follows a scaling relationship with two self-similar regions, one for the entanglement and terminal zone, and a second one for the transition to the glass. This can be described in its most general form (termed BSW spectrum) as H() = H _e ^ne + H _g ^– n _g for < _max and H() = 0 for _max < , where H _e , H _g , n _e , n _g are material constants and _max is the molecular weight dependent cut-off of the self-similar behavior. In this study, the dynamic mechanical response has been measured and analyzed for four highly entangled, nearly monodisperse polybutadienes with molecular weights from 20000 to 200000. The data are well represented by the BSW spectrum with scaling exponents of n _e = 0.23 and n _g = 0.67. The values of the exponents obtained in this work are about the same as those found for polystyrene samples in a previous study. This suggests that the two types of polymers have a similar relaxation pattern. However, at this point further refinement of the experiments is needed before being able to draw definite conclusions about the universality of the exponents.Dedicated to Professor Arthur S. Lodge on the occasion of his 70th birthday and his retirement from the University of Wisconsin.