Poly(diphenylacetylene)s with Electron‐Donating Alkoxy and Electron‐Withdrawing Fluoroalkyl Groups: Effect of the Substituent on Fluorescence

New poly(diphenylacetylene)s with alkoxy and fluoroalkyl groups as electron‐donating and electron‐withdrawing groups, respectively, were synthesized by using a WCl₆‐n‐Ph₄Sn catalyst. The polymer solutions emitted strong, bluish‐green lights when photo‐excited. The polymers that contained the electron‐donating alkoxy groups showed longer fluorescence‐maximum peaks when compared to the polymers that contained the electron‐withdrawing fluoroalkyl groups. However, such an effect of the substituent on the absorption property was not clearly seen. The emission bands of the solid films did not show any significant red shift, relative to that of the dilute solution.

     

Combinatorial Therapeutic Effect of Inhibitors of Aldehyde Dehydrogenase and Mitochondrial Complex I,and the Chemotherapeutic Drug,Temozolomide against Glioblastoma Tumorspheres

Resident cancer cells with stem cell-like features induce drug tolerance, facilitating survival of glioblastoma (GBM). We previously showed that strategies targeting tumor bioenergetics present a novel emerging avenue for treatment of GBM. The objective of this study was to enhance the therapeutic effects of dual inhibition of tumor bioenergetics by combination of gossypol, an aldehyde dehydrogenase inhibitor, and phenformin, a biguanide compound that depletes oxidative phosphorylation, with the chemotherapeutic drug, temozolomide (TMZ), to block proliferation, stemness, and invasiveness of GBM tumorspheres (TSs). Combination therapy with gossypol, phenformin, and TMZ induced a significant reduction in ATP levels, cell viability, stemness, and invasiveness compared to TMZ monotherapy and dual therapy with gossypol and phenformin. Analysis of differentially expressed genes revealed up-regulation of genes involved in programmed cell death, autophagy, and protein metabolism and down-regulation of those associated with cell metabolism, cycle, and adhesion. Combination of TMZ with dual inhibitors of tumor bioenergetics may, therefore, present an effective strategy against GBM by enhancing therapeutic effects through multiple mechanisms of action.     

Synthesis of novel 1,4-, 3,4-, and 4,5-dihydropyrimidines: First successful POCl3 chlorination and regioselective alkoxycarbonylation

Chlorination of 5,6-dihydropyrimidine-4-(3H)-one derivatives (1) with POCl₃ gave 1,4(3,4)-dihydropyrimidines (3), whose alkoxycarbonylation (ClCOOREt₃N or NaH) afforded regioselectively novel compounds (4). A new Pummerer rearrangement of compound (1, X= ---S(O)CH₃) with ₃, gave compound (5h).     

Der geschwindigkeitsbestimmende Schritt bei der Decarboxy-lierung von 2,4-Dihydroxybenzoesäure in mässig konzentrierter wässeriger Salzsäure

The decarboxylation kinetics of 2,4-dihydroxybenzoic acid have been studied in 0.1–8 N aqueous HCl at 50°. At low HCl concentrations, the observed first order rate constant, k, increases with increasing acidity of the solution. In solutions with 3.5–6 N HCl, k remains constant. The D₂O solvent isotope effect decreases from ^kH₂O/^kD₂O = 2.0 in 1N HCl to 1.3 in 5 N HCl, and it remains unchanged at 1.3 if the HCl concentration is increased further to 8 N. It is concluded that an increase of the acidity of the solution causes a change of the rate determining step from slow proton transfer to rate limiting C? C bond cleavage.     

Catalyzing methanolysis of alkyl halides in the interior of an amphiphilic molecular basket

A molecular basket with four cholate units assembled on a cone-shaped calix[4]arene assumed reversed micelle-like conformation in 5% methanol/carbon tetrachloride. The inwardly facing hydroxyl groups on the cholates concentrated the polar solvent from the mostly nonpolar mixture. Methanolysis of alkyl halides benefited from the concentrated pocket of methanol if the substrate was capable of entering the basket. Substrates that were too large or too hydrophobic to fit within the basket showed no rate acceleration.     

Product ion studies of diastereomeric benzo[ghi]fluoranthene tetraols by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and post-source decay

The product ion formation characteristics of the four diastereomeric tetrahydroxy benzo[ghi]fluoranthene compounds formed by hydrolysis of the syn and anti diastereomers of trans-3,4-dihydroxy-5,5a-epoxy-3,4,5,5a-tetrahydrobenzo[ghi]fluoranthene are studied using matrix-assisted laser desorption/ionization and post-source decay (PSD) to determine a correlation between the fragmentation characteristics of these tetraols and the structures of the diol-epoxide diastereomers from which they are hydrolyzed. The tetraols formed by the trans ring opening of the diol epoxides during hydrolysis yield product ion spectra specific for the syn and anti configurations of their precursor diol epoxides. All four diastereomeric tetraols form product ions by the losses of one and/or two water molecules in varying proportions when lithium-cationized molecule ions (m/z 301) are selected for PSD product ion analysis. The differences in the PSD spectra of these four Li+-cationized molecules are rationalized in terms of a water loss mechanism that involves the 1,2 elimination of a hydrogen atom and hydroxyl group that are cis with respect to each other on adjacent carbons.     

Apparent hydrodynamic thickness of densely grafted polymer layers in a theta solvent

We study the drainage of a near-theta solvent through densely grafted polymer layers and compare to recent notions that these layers display little permeability to solvent flow at surface separations less than a “hydrodynamic thickness.” The solvent is trans-decalin (a near-theta solvent at the experimental temperature of 24°C). The polymer is polystyrene (PS) end-attached to two opposed mica surfaces via the selective adsorption of the polyvinylpyridine (PVP) block of a PS-PVP diblock copolymer. The experimental probe was a surface forces apparatus modified to apply small-amplitude oscillatory displacements in the normal direction. Out-of-phase responses reflected viscous flow of solvent alone—the PS chains did not appear to contribute to dissipation over the oscillation frequencies studied. The value of the hydrodynamic thickness (R_H) was less than the coil thickness (L_o) measured independently from the onset of surface–surface interactions in the force-distance profile, implying significant penetration of the velocity field into the polymer layer. As the surface–surface separation was reduced from 3L_o to 0.3L_o, the apparent hydrodynamic thickness (R) decreased monotonically to values R ≪ R_H. Physically, this indicates that the “slip plane” moved progressively closer to the solid surfaces with decreasing surface–surface separation. This was accompanied by augmentation of the effective viscosity by a factor of up to approximately 5, indicating somewhat diminished permeability of solvent through the overlapping polymer layers. Similar results hold for the flow through surface-anchored polymers in a good solvent. It is interesting to note the strong stretching of densely end-grafted polymers in a theta solvent. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2961–2968, 1997     

Electro-optic applications of soluble polypyrrole

The optical transmittance of the film spin-cast from the polypyrrole(PPy) solution in chloroform depended on the thickness of the film. The film with 80% transmittance showed a surface resistivity of 23kΩ/□. A TN-LCD cell with rubbed PPy films as the LC alignment layers responded properly to an applied potential of 3.0V. Reflective mode cholesteric LCD cells made with black PPy film electrodes responded to AC fields to switch between the planar and focal conic states. PPy with imine structures introduced by deprotonation of doped PPy with NaOH solution was used as a diode material to exhibit a photo-current on exposing to light.