Boron-boron σ-bond formation by two-electron reduction of a H-bridged dimer of monoborane

Diborane(6) as a H-bridged dimer of monoborane can be converted cleanly by two-electron reduction into diborane(6) dianion, which is isoelectronic with ethane, through B-B σ-bond formation when each boron atom has a bulky ligand on it. The existence of the B-B σ bond is supported by the X-ray molecular structure [B-B bond length of 1.924(3) ?], NMR studies, magnetic susceptibility measurements, and DFT calculations. Stepwise hydride abstraction reactions of the diborane(6) dianion produce the corresponding H-bridged diborane(5) anion and doubly H-bridged diborane(4) without B-B bond scission.     

Fusarisetin A, an acinar morphogenesis inhibitor from a soil fungus, Fusarium sp. FN080326

An acinar morphogenesis inhibitor named fusarisetin A (1) that possesses both an unprecedented carbon skeleton and a new pentacyclic ring system has been identified from an in-house fractionated fungal library using a three-dimensional matrigel-induced acinar morphogenesis assay system. The structure of 1 was determined in detail by NMR and circular dichroism spectroscopy, X-ray analysis, and chemical reaction experiments.     

Synthesis of a Stable N‐Hetero‐RhI‐Metallacyclic Silanone

A novel N‐hetero‐Rh^I‐metallacyclic silanone 2 has been synthesized. The silanone 2 , showing an extremely large dimerization energy (ΔG=+86.2 kcal mol^?1), displays considerable stability and persists in solution up to 60 °C. Above 120 °C, an intramolecular C_sp3?H insertion occurs slowly over a period of two weeks leading to the bicyclic silanol 5 . The exceptional stability of 2 , related to the unusual electronic and steric effects of Rh^I‐substituent, should allow for a more profound study and understanding of these new species. Furthermore, the metallacyclic silanone 2 presents two reactive centers (Si=O and Rh), which can be involved depending upon the nature of reagents. Of particular interest, the reaction with H₂ starts with the hydrogenation of Rh^I center leading to the corresponding Rh^III‐dihydride complex 7 and it undergoes a cis/trans‐isomerization via a particular mechanism, demonstrating that addition‐elimination processes can also happen for silanones just like for their carbon analogues!     

18π‐Electron Tautomeric Benziphthalocyanine: A Functional Near‐Infrared Dye with Tunable Aromaticity

Dihydroxybenziphthalocyanine 1 , with bulky aryloxy groups, has been synthesized and characterized by X‐ray crystallography, NMR and UV/Vis‐NIR spectroscopy, and theoretical calculations. Macrocycle 1 is the first example of an aromatic benziphthalocyanine with an 18π‐electron structure, and was found to exist as an equilibrium mixture of weakly aromatic and strongly aromatic tautomers. The aromaticity and near‐IR absorption can be controlled by chemical modification at the reactive resorcinol moiety and by variation of the solvent.     

ACCESSORY CELL ABILITY OF LANGERHANS CELLS FOR SUPERANTIGEN IS RESISTANT TO ULTRAVIOLET-B LIGHT

Abstract We examined the effects of ultraviolet-B (UVB) irradiation on the accessory cell ability of Langerhans cells (LC) to induce a T-cell response to a superantigen, staphylococcal enterotoxin B (SEB). The ability of LC-enriched epidermal cells (LC-EC) to evoke a T-cell response to SEB was retained at the doses of UVB (up to 40 mJ/ cm²) that profoundly affected the antigen-presenting function of LC-EC for a hapten, trinitrophenyl (TNP), and a protein antigen, conalbumin. Thus, the LC accessory function for superantigens is more resistant to UVB irradiation than that for ordinary antigens. This UVB resistance is presumably due to no requirement of antigen processing for superantigens as chemically fixed or chloroquine-treated LC-EC still retained their ability to induce T-cell responses to SEB. Higher doses of UVB (more than 60 mJ/cm²) reduced the accessory cell ability of LC-EC for SEB up to 50% of control. The addition of monoclonal antibodies against adhesion molecules between LC and T cells to the culture resulted in substantial suppression of the T-cell response to SEB induced by nonirradiated LC-EC, while the U VB-irradiated LC-EC-induced T-cell response was not significantly blocked with these monoclonal antibodies. This suggested that the reduction of LC ability for superantigen by high doses of UVB is at least partly due to impairment of adhesion molecules on LC by UVB irradiation.     

Creation of magnetic cerasomes through electroless plating and their manipulation using external magnetic fields

Magnetic cerasome, an artificial cell membrane having ultrathin magnetic metal layers on the surface, was prepared through electroless plating of magnetic metal alloy onto an organic–inorganic vesicular nanohybrid “cerasome.” Morphological and functional characteristics of the magnetic cerasome were evaluated using various physical measurements: scanning and transmission electron microscopies, energy-dispersive X-ray spectroscopy, electron tomography, and vibrating sample magnetometry. The results proved that high morphological stability of the cerasome was important for constructing the magnetic lipid vesicle and that insertion of an alkylated metal ligand into the cerasome was essential to the magnetic metal alloy deposition on the cerasome surface. Fluorescence microscopic observations revealed that the magnetic cerasomes were collected reversibly on the slide glass surface and manipulated depending on external motion of a magnet. The potential use of the magnetic cerasomes as a novel vesicular nanohybrid is also described in this report.     

Coverage dependence of superstructures and phase transitions of Pb on the Ge(100)2 × 1 surface

We report an STM investigation of the Pb adsorption on the Ge(100)2 × 1 surface. With the increase of the Pb coverage, the evolution of the surface structure and surface morphology was revealed on an atomic scale. We also observed some new structures which could not be identified previously in LEED observations. The observed surface morphology evolution indicates that Pb is indeed very reactive and mobile on the Ge(100) surface.     

Fabrication of Periodic Waveguides Using Organic Crystals and Fluorinated Polyimides for Quasi-Phase-Matched Second-Harmonic Generation

We have developed a new method to fabricate periodic waveguide structures used for quasi-phase-matched second-harmonic generation, where nonlinear optical organic crystals and fluorinated copolyimides are alternately arranged. Quasi-phase-matched second-harmonic generation from an organic waveguide device has been demonstrated.     

Cis and trans 4,8-dimethyl-6-phenyl-5,6,7,8-tetra-hydro-4H-1,3,6-oxadiazocin-2-ones: Conformational studies and configurational assignments by NMR

The reaction of N-(2-aminopropyl)-N-(2-hydroxypropyl)aniline with phosgene afforded cis and trans isomers of 4,8-dimethyl-6-phenyl-5,6,7,8-tetrahydro-4H-1,3,6-oxadiazocin-2-one. On the basis of ASIS data and Eu-shift difference, the title compounds are found to exist as boat-chair conformation in which the carbonyl carbon resides at the BC-2 position on the molecular plane.