Enantioselective Synthesis of AG‐041R by using N‐Heteroarenesulfonyl Cinchona Alkaloid Amides as Organocatalysts

The organocatalytic enantioselective decarboxylative addition of malonic acid half thioesters to ketimines derived from isatins by using N‐heteroarenesulfonyl cinchona alkaloid amides afforded products with high enantioselectivity. The products could be converted into optically active AG‐041R. X‐ray crystallographic analysis revealed that the hydrogen bonding between the sulfonimide proton and the 8‐quinolyl nitrogen atom plays an important role in exerting the enantioselectivity of the reaction.     

Promotion effects of optical antipodes on the formation of helical fibrils: chiral perfluorinated gelators

A chiral gelator, RR- or SS-N,N'-diperfluorooctanoyl-1,2-diaminocyclohexane, gelated racemic 2-butanol. The gel was most stable at the racemic mixture, its stability lowered with the increase in the optical purity of the gelator. Notably, characteristic helically coiled fibrils were formed in the narrow region of enantiomer excess (ee = 0.2-0.4). Promotion effects of the antipodal enantiomers are proposed.     

A new class of flavonoids bearing macrocyclic polyethers by stereoselective photochemical cycloaddition reaction

A new class of flavonoids bearing cyclic polyethers involving a phenyl ring was conveniently provided by the intramolecular photochemical dimerization of 2-chromonecarboxylic esters. Irradiation of 2-chromonecarboxylate with a polyether tethered at both ends promoted intramolecular [2 + 2] cyclobutane formation leading to 14- to 27-membered cyclic polyethers. The efficiency depended on the substituted position of the phenyl ring, with ortho- and meta-substituted derivatives giving cycloadducts in good chemical yields and quantum efficiencies, whereas the para-derivatives were inert toward photolysis. X-ray crystallographic analysis revealed that the stereochemistry of the macrocyclic cycloadducts exhibited C₂-symmetry.     

Novel drug delivery device using silicone: controlled release of insoluble drugs or two kinds of water-soluble drugs

Drug release mechanism from silicone carrier differs depending on physicochemical properties of the drug. So far, there have been few reports on controlled release of insoluble drug and on simultaneous release of two kinds of water-soluble drugs. The purposes of this study are to establish methods for (1). continuous release of insoluble drug, and (2). release of two kinds of water-soluble drugs from silicone carrier. Polystyrene beads (PSTB) and proteins such as interferon (IFN) and human serum albumin (HSA) were used as model drugs. PSTB was released from silicone only when citric acid (CA) and sodium bicarbonate (SB) existed as additives. The release patterns of IFN and HSA were almost same in the case of matrix and covered-rod formulations, but double-layered formulation released them in different patterns. As far as we are aware, this is the first report on the release of insoluble drug from silicone and the controlled release of two kinds of water-soluble drugs.     

The effect of stress induced anisotropy on shear band formation

Summary This paper describes the effect of non-coaxiality arising from material anisotropy on bifurcation phenomena such as shear band formation. The elasto-plastic model originally proposed by Sekiguchi and Ohta [7] is one of the typical models which include anisotropy and it is used to examine the effect of anisotropy on shear band formation. First, we shall extend this elasto-plastic model for infinitesimal strain to a model for finite strain and discuss the mathematical structure of this model. The stress induced anisotropy is found to bring about a vertex-like effect, such as the non-coaxiality between the Cauchy stress tensor and a plastic stretching tensor, into the constitutive relation. Then, we shall examine the effect of this non-coaxiality on bifurcation conditions in relation to the material rigidity which changes with the angle of simple shear. Finally, it will be concluded that this non-coaxiality arising from the anisotropy does not contribute much to triggering instability by localization of the deformations which result in shear band formation, while on the other hand, the non-coaxiality due to the yield vertex effect is rather inclined towards instability by localization of the deformations.

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Der Einfluß spannungsinduzierter Anisotropie auf die Scherzonenbildung

Übersicht Beschrieben wird der Einfluß anisotropie-bedingt verschiedener Achsen von Spannung und Deformationsgeschwindigkeit auf Verzweigungsphänomene wie die Scherzonenbildung. Das elastisch-plastische Modell von Sekiguchi und Ohta wird als typisch anisotropes Modell zur Untersuchung des Einflusses der Anisotropie auf die Scherzonenbildung benutzt. Zunächst wird es zu einem Modell für endliche Deformationen erweitert und seine mathematische Struktur erörtert. Es zeigt sich, daß die spannungsinduzierte Anisotropie einen Effekt ähnlich einer Fließortspitze erzeugt wie z. B. verschiedene Achsen von Cauchy-Spannungstensor und plastischem Strecktensor. Danach wird in Zusammenhang mit der Materialsteifigkeit, die vom Winkel der einfachen Scherung abhängt, der Einfluß verschiedener Achsen auf Verzweigungsbedingungen untersucht. Es wird gefolgert, daß anisotropie-bedingt verschiedene Achsen wenig zur Auslösung der Instabilität durch lokalisierte Deformation beitragen, andererseits verschiedene Achsen infolge einer Fließortspitze die Neigung zur lokalisierten Deformation unterstützen.

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Presented at the workshop on Numerical Methods for Localization and Bifurcation of Granular Bodies, held at the Technical University of Gadansk (Poland), September 25–30, 1989     

Ring opening of aryl cyclopropyl ketones to l-Acyl-l,l,3-tribromo- propanes and their cyclization to 2-Aryl-3,3-dibromo-2-methoxy and -2-cyanotetrahydrofurans

The reaction of aryl cyclopropyl ketones 1 with excess bromine gave l-acyl-l,l,3-tribromopropanes 2 , which were cyclized to 2-aryl-3,3-dibromo-2-methoxytetrahydrofurans 3 on treatment with alkaline in aqueous methanol. 2-Aryl-3,3-dibromo-2-cyanotetrahydrofurans 5 were obtained by the reactions of 2 with sodium cyanide.