Candicanoside A,a Novel Cytotoxic Rearranged Cholestane Glycoside from Galtonia candicans

A novel cholestane diglycoside, named candicanoside A ( 1 ), was isolated from the bulbs of Galtonia candicans by monitoring the cytotoxic activity on HL‐60 leukemia cells. Candicanoside A ( 1 ) is very unique in structure, having two epoxy functionalities in its rearranged cholestane skeleton, and showed differential cytotoxicity in the Japanese Foundation for Cancer Research 38 cell‐line assay.     

Shear flow effect on phase behavior and morphology in polymer blends

The effect of simple shear flow on the phase behavior and morphology was investigated for both polystyrene/poly(vinyl methyl ether) (PS/PVME) and poly(methyl methacrylate)/poly(styrene‐co‐acrylonitrile) (PMMA /SAN‐29.5) blends, which have LCST (lower critical solution temperature)‐type phase diagram. The measurements were carried out using a special shear apparatus of two parallel glass plates type. The PS/PVME blends showed shear‐induced demixing and shear‐induced mixing at low and high shear rate values, respectively. In addition, the rotation speed and the sample thickness were found to have a pronounced effect on the phase behavior under shear flow. On the‐other hand, PMMA/SAN blend showed only shear‐induced mixing and the magnitudes of the elevation of the cloud points were found to be composition and molecular weight dependent. The morphology of the PMMA/SAN=75/25 blend indicated that shear‐induced mixing occurred at a critical shear rate value, below which the two phases were highly oriented and elongated in the flow direction.     

Synthesis of regiocontrolled poly(4,6-di-n-butoxy-1,3-phenylene) by oxidative coupling polymerization

Poly(4,6-di-n-butoxy-1,3-phenylene) ( 6 ) was prepared by oxidative coupling polymerization of 1,3-di-n-butoxybenzene ( 1 ) or 2,2′,4,4′-tetra-n-butoxy biphenyl (3). Polymerizations were conducted in nitrobenzene in the presence of FeCl₃ at room temperature and produced polymers with number-average molecular weights up to 42,000. The effects of various factors, such as amount of FeCl₃ and reaction temperature and time were studied. The structure of polymer 6 was characterized by 270 MHz ¹H- and 68.5 MHz ¹³C-NMR spectroscopies and was estimated to consist of almost completely 1,3-linkage. The regiocontrolled polymer was readily soluble in common organic solvents. Thermogravimetric analysis of polymer 6 showed 10% weight loss at 390°C in nitrogen. © 1997 John Wiley & Sons, Inc. J Polym Chem 35 : 2259–2266, 1997     

An organic electroluminescent device with a molecularly doped polymer hole transport layer

Electroluminescent(EL) devices have been fabricated using four different polymers with different glass transition temperatures (T_g) dispersed with N,N′-bis-(3-methylphenyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine (TPD) as a hole transport layer and tris(8-hydroxyquinoline) aluminum (Alq₃) as an emitting layer. It was found that the higher the T_g of the polymer, the longer the lifetime of the device. From observations of TPD-doped polymer films with optical microscope and atomic force microscope, dispersing TPD in the polymers was found to suppress the crystallization that causes the roughness of the film surface. It was also observed that the higher the T_g of the host polymers, the more difficult TPD crystallization was. The property of the EL device with polyethersulfone (PES) dispersed with TPD was also investigated. The lifetime of EL device with the TPD doped PES film was improved more than five times at a current density below 10 mA/cm² compared with the device with a conventional TPD hole transport layer. © 1997 John Wiley & Sons, Ltd.     

Synthesis of Immobilized CMP-Sialic Acids and Their Enzymatic Transfer with Sialyltransferase

A novel immobilization procedure for glycoproteins is based on the reacion of immobilized CMP-NeuAc (CMP-sialic acids) with sialyltransferase (see scheme). The transfer ability was tested under various conditions; a corresponding oligosaccharide or asialoglycoprotein acted as sialyl acceptor. The solid-phase synthesis of CMP-NeuAc is also described.     

A ferroelectric barium titanate,BaTi2O5

The crystal structure of monobarium dititanium pentaoxide, BaTi₂O₅, synthesized by a floating‐zone method, was studied by X‐ray diffraction. Previous reports describe the structure as being in the monoclinic centrosymmetric space group C2/m. We have recently found that this material exhibits ferroelectricity, and therefore BaTi₂O₅ should have lower symmetry. The crystal structure of BaTi₂O₅ was refined in space group C2, revealing a displacement of the Ti atoms along the b axis. This result is consistent with the fact that the ferroelectricity of BaTi₂O₅ was only observed along the b axis.