Lipase-catalyzed asymmetric desymmetrization of prochiral 2,2-disubstituted 1,3-propanediols using 1-ethoxyvinyl benzoate

The lipase-catalyzed asymmetric desymmetrization of the prochiral 2,2-disubstituted 1,3-propanediols was studied using various types of 1-ethoxyvinyl esters (1a-i). Although 1a-e with aliphatic acyl groups were not sufficient, use of the benzoate (1f) in combination with Candida rugosa lipases converted acyclic diols (2, 6) and cyclic diols (11-14) to the optically active compounds (3f, 7f, 15f-18f), bearing a quaternary carbon center, with moderate-to-high optical yields. These products were fairly stable against racemization under acidic conditions.     

Silicon-carbon unsaturated compounds. 77. Thermal behavior of cis- and trans-1-silacyclobut-3-ene formed from pivaloyl[tert-butylbis(trimethylsilyl)]silane and tert-butylacetylene

The reaction of tert-butylbis(trimethylsilyl)silyl potassium with pivaloyl chloride gave pivaloyl[tert-butylbis(trimethylsilyl)]silane (1) in 89% yield. The cothermolysis of 1 with tert-butylacetylene at 140 °C for 24 h produced the mixture consisting of cis- and trans-1,2,3-tri(tert-butyl)-2-(trimethylsiloxy)-1-(trimethylsilyl)-1-silacyclobut-3-ene (cis-2 and trans-2) in a ratio of 0.7: 1, in 88% combined yield. The thermolysis of the mixture, cis-2 and trans-2, at 250 °C for 24 h proceeded to give trans-1,2,4-tri(tert-butyl)-1-(trimethylsiloxy)-2-(trimethylsilyl)-1-silacyclobut-3-ene (4) as a single product in 96% yield. Similar treatment of cis- and trans-2 at 190 °C for 15 h afforded silylcyclopropene 3 quantitatively, which underwent further isomerization at 250 °C to give trans-1-silacyclobut-3-ene 4 in quantitative yield.     

Role of each part of cyanobiphenyl-containing polymers in porous-film preparation by using the breath-figure method

ABSTRACT

The breath-figure method using the condensation of water droplets can easily fabricate regular porous films. Although the method is simple, the phenomenon itself requires the control of many parameters that change throughout the process. Therefore, we require a unified understanding of polymers for the fabrication of ordered porous films. In this study, to clarify the required molecular structures of polymers to form a regular porous structure, we systematically explored poly(methacrylate)s with cyanobiphenyl moieties connected by dodecyl groups in the side chain (P11CB); these could form a hexagonal ordered porous structure on the entire film surface. The comparison of P11CB and P11B, which is a P11CB without cyano groups, showed that the local polar groups in hydrophobic polymers promote the formation of ordered porous films. Furthermore, no holes were formed in films of P0CB which is a P11CB without alkyl spacers due to its hydrophilicity. Long alkyl chains resulted in changed hydrophilic polymers to hydrophobic polymers. The introduction of long alkyl chains as a spacer between the biphenyl moiety and polymer backbone is preferred in the cases of particularly few amounts of biphenyl groups in the polymer. The biphenyl groups showed the ability to improve film formability.     

Soluble and film-formable homopolymer tethering side-opened cage silsesquioxane pendants

Cage silsesquioxane, denoted as polyhedral oligomeric silsesquioxane (POSS) has high crystallinity to readily cause aggregation when it is induced into polymer side chain. In this work, side-opened POSS was employed to construct a bifunctional monomer for cyclopolymerization. The collapsed symmetry of the POSS core effectively reduced the crystallinity to realize homogeneous films, while a traditional POSS homopolymer formed turbid and brittle films. The obtained film showed high transparency and thermal stability.     

Inclusion Complexation of a Seleno-Organic Antioxidant, Ebselen, with Cyclodextrins in Aqueous Solution

The interaction of ebselen, 2-phenyl-1,2-benzisoselenazol-3(2H)-one, a novel neuroprotective agent, with cyclodextrins (CyDs) in aqueous solution was studied by the solubility method and spectroscopic methods. The ability of sulfobutyl ether -CyD (SBE7--CyD, average degree of substitution= 6.2) to solubilize ebselen was greater, and its stability constant (> 2000 M^-1) was significantly higher than those (< 1000 M^-1) of other CyD complexes employed. The stability constant of the complexes rose as hydrophobicity of the substituents of CyDs increased, whereas it was negligibly affected by change in ionic strength of the medium, indicating a significant contribution of hydrophobic interaction in the complexation. SBE7--CyD gave positive and negative CD bands at around 320 and 350 nm, respectively, indicating that the guest is embedded in the asymmetric locus of the CyD cavity. ¹H-NMR spectroscopic studies suggested that the mono-substituted benzene ring of ebselen is preferably included in the cavity of SBE7--CyD. The results indicate that SBE7--CyD is useful as a solubilizing agent for ebselen.     

Simultaneous Measurement of Velocity and Fluctuating Pressure in a Turbulent Wing-tip Vortex Using Triple Hot-film Sensor and Miniature Total Pressure Probe

We have developed a probe-system for simultaneous measurement of three velocity components and pressure in turbulent flows. A miniature total pressure probe is placed adjacent to the sensors of a triple hot-film probe in order to achieve the spatial resolution which is equivalent to that of the triple hot-film probe itself. The instantaneous static pressure is calculated from measured velocity and total pressure by means of a newly developed processing method based on the Bernoulli equation for unsteady flows. The measurements were undertaken in a turbulent wing-tip vortex flow. The look-up table method is employed for the calibration of the hot-film probe so accurate velocity data could be obtained over a wide range of the flow-attack angles. It is also demonstrated that the present probe-system is capable of measuring fluctuations in both velocity and pressure in the 20?C650 Hz frequency range. The distribution of the fluctuating pressure obtained by this indirect method is in good agreement with the results from direct measurements of static pressure, demonstrating the promising performance of the present method. Furthermore, an improvement in the ability to make measurements of the velocity?Cpressure correlation across the wing-tip vortex is achieved. This improvement is possible because the effects of lateral velocity components are properly taken into account in the present formulation. The investigation regarding the transport equation budget for turbulent kinetic energy shows an anomalous structure of turbulence in this flow, mainly due to the meandering of the vortex, and the measurement of pressure diffusion is found to play an important role in the characterization of this kind of flow.     

Ab initio MO analysis of interaction paths between radicals in ferromagnetic organic systems

Interaction path analyses for pi-conjugated organic systems were performed at the ab initio molecular orbital level to examine the relationship between inter-radical interactions and the high-spin stability of the system. It was found that the high-spin stability results from through-bond interactions between radicals, not from through-space interactions, in relation to the stabilization of a low-spin state due to the effects of electron correlation. L(ij)(min) value for estimating the mixing of nonbonding molecular orbitals well predicted the relationship between the through-bond interactions and the high-spin stability. Furthermore, molecular orbital calculations revealed that the all-trans type interaction path between radicals produces long-range exchange interactions, and the additivity of high-spin stability is observed by keeping short-range through-bond interaction paths.     

Permanence and global stability of a class of discrete epidemic models

In this paper we investigate the permanence of a system and give a sufficient condition for the endemic equilibrium to be globally asymptotically stable, which are the remaining problems in our previous paper (G. Izzo, Y. Muroya, A. Vecchio, A general discrete time model of population dynamics in the presence of an infection, Discrete Dyn. Nat. Soc. (2009), Article ID 143019, 15 pages. doi:10.1155/2009/143019.)