π-Cyclization: The synthesis of (±)-solavetivone and (±)-hinesol

A general efficient approach leading to the total synthsis of (±)-solavetivone, (±)-hinesol, and related spirovetivanes, is described. The process involves stereoselective formation of the asymmetric center at C-7 by π-cyclization as a key step.     

Effect of solvent on single crystal formation from dilute polyethylene solution

Summary To investigate the effect of solvent on polyethylene single crystal formation, the end surface free energy of lamellae was estimated from the dissolution temperature of single crystal in solvent from which single crystals were formed, by the equation based on the thermodynamic consideration. The density measurements of the single crystal were also carried out in a density gradient column, further to obtain informations about solvent effect on single crystal formation. From the results on the end surface free energy and the density of single crystals, the conclusion obtained in the preceding paper, that more regular surface may be formed with solvent having larger thermodynamic interaction parameter and larger molar volume, was confirmed.

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Zusammenfassung Die freie Oberflächenenergie von Polyäthylenkristallen wurde aus der Auflösungstemperatur der Kristalle in dem Lösungsmittel, aus dem sie gebildet wurden, über thermodynamische Betrachtungen abgeschätzt.Aus der Größe der freien Oberflächenenergie und der Dichte der Einkristalle wurde die in der vorhergehenden Veröffentlichung angegebene Folgerung bestätigt, daß die Oberfläche um so regelmäßiger ausgebildet wird, je größer der thermodynamische Wechselwirkungsparameter und das Molvolumen des Lösungsmittels sind.

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The authors wish to express thanks to ProfessorB. Wunderlich for giving them the polyethylene sample. Thanks are also due to ProfessorI. Sakurada for the facilities in the low-angle X-ray measurements.     

On the regioselectivity for the Michael addition of thiols to unsymmetrical fumaric derivatives

The regiochemistry of the Michael addition of thiols to unsymmetrical fumaric derivatives was investigated. Conjugate addition of thiols to unsymmetrical fumaric diester was well controlled by the presence of lithium cation and one of the two possible regioisomers was prepared in a highly selective manner. Fumaric ester amides underwent the regioselective Michael addition that was controlled by the presence or absence of the base; either of the regioisomers was prepared as an almost diastereomerically pure form. The present control of the regiochemistry can be explained by the factors of change of active site for the addition by the coordination or non-coordination of proton or lithium cation to the carbonyls. To clarify the origin of the regioselectivity, the relative rates of the conjugate addition of thiol to acrylate derivatives were measured under competitive conditions. Ethyl acrylate reacted with thiol faster than tert-butyl acrylate and the rate difference was enhanced by the presence of lithium cation. In the presence of base, ethyl acrylate gave the adducts much faster than acrylamide, while under non-basic conditions acrylamide showed higher reactivity than the ester. This regioselectivity was also observed in the Michael/aldol reaction and multi-substituted γ-butyrolactones were prepared in a stereoselective manner. The thio groups introduced here served as a leaving group and a convenient stereoselective synthesis of β-, γ- and δ-lactams was developed.     

Freedom in electroweak symmetry breaking and mass matrix of fermions in dimensional deconstruction model

There exists a freedom in a class of four-dimensional electroweak theories proposed by Arkani-Hamed et al. relying on deconstruction and Coleman–Weinberg mechanism. The freedom comes from the winding modes of the link variable (Wilson operator) connecting non-nearest neighbours in the discrete fifth dimension. Using this freedom, dynamical breaking of SU(2) gauge symmetry, mass hierarchy patterns of fermions and Cabbibo–Kobayashi–Maskawa matrix may be obtained.     

The coagulation of particles in suspension by freezing-thawing

Summary Freeze-thaw coagulation can be prevented by keeping unfrozen water which is attained by adding hydrophilic substances to the suspension. The effectiveness is due to the prevention of the growth of ice crystals due to the existence of unfrozen water, thus the approach of particles due to crowding from growing ice crystals is suppressed. The greater the proportion of the unfrozen water, the lesser the coagulation, and the stronger the hydrophilic property of the additive, the greater proportion of residual unfrozen water.It was also clarified that there were three factors, all of which were useful for preventing coagulation: namely, (A) the presence of large amounts of unfrozen water, (B) a short plateau on the freezing curve, if present, (C) the presence of small residual ice crystals. These were identical in their mechanism for preventing coagulation, namely the prevention of coagulation by controlling ice crystal growth.Theoretical calculations of the distances between particles at the same suspension concentration showed that small particles coagulate more easily as compared with large ones.

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Zusammenfassung Die Gefrierkoagulation kann verhindert werden durch die Beibehaltung von nicht gefrorenem Wasser, was durch den Zusatz von hydrophilen Substanzen zu den Suspensionen erreicht wird. Je größer der Anteil des nicht gefrorenen Wassers ist, um so geringer ist die Koagulation, und je stärker die hydrophile Eigen schaft des Additivs ist, um so größer ist der Anteil des nicht gefrorenen Wassers.Es wurde weiterhin klargestellt, daß es drei Faktoren für die wirksame Verhüg der Koagulation gibt: (A) die Gegenwart großer Mengen nicht gefrorenen Wassers, (B) ein kurzes Plateau an der Gefrierkurve, falls vorhanden, (C) kleine bleibende Eiskristalle. Sie sind in ihrem Mechanismus der Koagulationsverhütung identisch, nämlich der Verhütung der Koagulation durch die Kontrolle des Wachstums der Eiskristalle.Theoretische Berechnungen der Abstände zwischen Partikeln bei gleicher Konzentration der Lösung zeigen, daß kleine Partikeln leichter als große Partikeln koagulieren.

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With 16 figures     

Configurational studies on amylose. I. Scattering functions

Scattering functions for amylose chains have been calculated as a statistical mechanical average over eligible configurations based on the rotational isomeric state approximation. Main emphasis has been placed on an intermediate-angle range (0.1 < h = (4π/γ)sinθ < 1.0 Å^?1) where the scattering function is sensitive to local chain configurations. In order to avoid overestimation of the regularity of chain configurations, the rotational isomeric states for each glycosidic bond have been defined by a set of discrete torsion angles at intervals of 5°. Pair correlation functions for atoms separated by sequences shorter than 31 glucose units are evaluated by the Monte Carlo method, while the interference for longer sequences is calculated by a series expansion in the even moments of the chain. All carbons and all skeletal oxygens are treated as point scatterers in order to incorporate all the interferences between atoms in unit pairs in the calculations. The calculated scattering function shows appreciable oscillation at intermediate angles, reflecting the characteristic helical tendency of the configurations. The Debye function is found to be inadequate in the intermediate-angle region owing to the non-Gaussian character of the distribution function and to breakdown of the assumption that the mean-square distance between a pair of atoms is proportional to the number of bonds between them, because of the bulkiness of the glucose unit.