Using triethynylphosphine ligands bearing bulky end caps to create a holey catalytic environment: application to gold(I)-catalyzed alkyne cyclizations

The synthesis, properties and catalytic uses of phosphinoalkynes bearing bulky end caps at the alkyne termini, that is, tris[(triarylsilyl)ethynyl]phosphines are reported. The most salient feature of the new phosphines is the holey molecular shape possessing a deep and large-scale metal-binding cavity. The holey phosphines displayed remarkable rate enhancement in the gold(I)-catalyzed six- and seven-membered ring forming cyclizations of acetylenic keto esters and 1,7-enynes. It is proposed that the cavity in the ligand forces a nucleophilic center (enol or alkene) of the acetylenic compounds close to the gold-bound alkyne, making ring-closing anti attack feasible.     

Measurements of electron beam damage for organic crystals in a high voltage electron microscope with image plates

The critical dose for extinction of the diffraction pattern from behenic acid monolayer crystals increased with increasing accelerating voltages. The mean values at 114, 500 and 1000kV were 0.6, 1.8 and 2.2 electrons/A(2), respectively. The critical dose at 500-1000kV is three or more times as large as that at 114kV. Considering this with the recent measured value of the detective quantum efficiency of the image plate, 0.5 at 500kV and 0.4 at 1000kV, 1.5 times as much information can be collected from a crystal at 500-1000kV as at 114kV. Therefore, the combined use of high voltage electron microscopy and image plate detectors offers a significant improvement over conventional electron microscopy approaches for the study of radiation sensitive organic molecule crystals.     

Synthesis of conjugated allenes through copper-catalyzed γ-selective and stereospecific coupling between propargylic phosphates and aryl- or alkenylboronates

A Cu-catalyzed γ-selective coupling reaction between propargylic phosphates and aryl- or alkenylboronates afforded aryl- or alkenyl-conjugated allenes. The reaction showed excellent functional group compatibility in both the propargylic substrates and the boronates. The reaction of an enantioenriched propargylic phosphate proceeded with excellent chirality transfer with 1,3-anti stereochemistry to give axially chiral aryl- and alkenylallenes.     

Recent advances in liver sinusoidal endothelial ultrastructure and fine structure immunocytochemistry

Ultrastructure reports have described that liver sinusoidal endothelial cell (LSEC)s contain a cytoskeletal framework of filamentous actin. Small G protein has emerged as an important regulator of the actin cytoskeleton, and consequently, of cell morphology and motility. We investigated actin filaments in relation to SEF in LSECs using a heavy meromyosin-decorated reaction and thereby elucidated the roles of small G protein and actin cytoskeleton in the morphological and functional alterations of SEF. Caveolin-1 expression has also been found in fenestrations with many characteristics of liver sinusoidal endothelial cells. Currently, fenestral studies and human disease are revealing ways to increase the liver sieve's porosity, which is reduced through pathological mechanisms. Hepatic sinusoidal endothelial dysfunction, which is known to impair endothelium-dependent relaxation in the liver microcirculation, contributes to increased intrahepatic vascular resistance.     

Spontaneous emission control of CdSe/ZnS nanoparticle monolayer in polymer nanosheet waveguide assembled on a one-dimensional silver grating surface

We present spontaneous emission control of a core-shell CdSe/ZnS nanoparticle array assembled with polymer ultrathin films consisting of polymer nanosheets on a silver grating substrate, which served as a unique and simple photonic cavity. The grating-coupled waveguide modes enabled 10(3) order luminescence enhancement and one-fourth spectral narrowing. The light emission from a CdSe/ZnS nanoparticle array can be controlled by tuning the film thickness of hybrid polymer nanoassemblies, which provides multiple emission performance with good tuning ability from red to green at low-power continuous wave laser excitation (～μW).     

Continuous flow metal-free oxidation of picolines using air

The metal free, direct oxidation of 2-, 3-, and 4-picoline to the corresponding carboxylic acid using either oxygen or air has been developed under continuous flow conditions. Complete conversion for all three substrates was obtained at moderate temperatures and pressures within minutes.     

A dimethoxytriazine type glycosyl donor enables a facile chemo-enzymatic route toward α-linked N-acetylglucosaminyl-galactose disaccharide unit from gastric mucin

An efficient chemo-enzymatic process for construction of the α-linked disaccharide unit (GlcNAcα1-4Gal) found in gastric mucin has been developed. The process consists of a one-step preparation of a novel triazine type glycosyl donor in water and the subsequent transglycosylation to a galactose derivative catalysed by α-N-acetylglucosaminidase.