在OsO_4催化作用下烯烃的立体选择性氧化反应

四氧化锇是一种贵而毒性大的试剂。本文介绍催化剂量的四氧化锇在立体选择性高的烯烃氧化反应中的应用，为四氧化锇在有机合成中的应用，开辟了新的途径。     

A preparation method for observing intracellular structures by scanning electron microscopy

In order to observe intracellular structures by scanning electron microscopy, excess cytoplasmic matrix must be removed from the fractured surface of cells. Previously we reported an Osmium-DMSO-Osmium method devised for this purpose. This method is very effective in revealing intracellular structures, but requires osmium tetroxide for initial fixation with some consequent disadvantages. In the present study, a revised Osmium-DMSO-Osmium method is reported, in which an aldehyde mixture is used as the initial fixative instead of osmium tetroxide. As fixation is carried out by perfusion in this revised method, better preservation of fine structures is achieved than by the original method, especially in the central nervous tissue which tends to suffer from post-mortem degeneration. Moreover this method can be applied to cytochemical studies of intracellular structures with a scanning electron microscope (SEM). In this study, acid phosphatase of lysosomes is demonstrated in a coloured SEM micrograph.     

Cytotoxic Triosmium Carbonyl Clusters: A Structure–Activity Relationship Study

A structure–activity relationship (SAR) study of the triosmium carbonyl cluster Os₃(CO)₁₀(NCCH₃)₂ was carried out with a series of clusters of the general formula Os₃(CO)_12?nL_n, cationic osmium clusters and a hemi‐labile maltolato‐Os cluster. The SAR results showed that good solubility in DMSO and at least one vacant site are required for cytotoxicity. In vitro evaluation of these new compounds showed that some are selectively active against estrogen receptor (ER)‐independent MDA‐MB‐231 breast cancer cell lines relative to ER‐dependent MCF‐7 breast cancer cells, suggesting that the compounds have a different biological target specific to MDA‐MB‐231 cells. In particular, the maltolato cluster exhibits strong antiproliferative activity, with an IC₅₀ value of 3 μM after only 24 h incubation. Additionally, biochemical assays conducted with the cationic cluster show that it induces apoptosis, although a biological target has not yet been identified. Further research to establish the molecular targets of these compounds and to develop improved organometallic clusters as potential breast cancer therapeutics is underway.     

Comparing different methods to fix and to dehydrate cells on alginate hydrogel scaffolds using scanning electron microscopy

Scanning electron microscopy (SEM) is commonly used in the analysis of scaffolds morphology, as well as cell attachment, morphology and spreading on to the scaffolds. However, so far a specific methodology to prepare the alginate hydrogel (AH) scaffolds for SEM analysis has not been evaluated. This study compared different methods to fix/dehydrate cells in AH scaffolds for SEM analysis. AH scaffolds were prepared and seeded with NIH/3T3 cell line; fixed with glutaraldehyde, osmium tetroxide, or the freeze drying method and analyzed by SEM. Results demonstrated that the freeze dried method interferes less with cell morphology and density, and preserves the scaffolds structure. The fixation with glutaraldehyde did not affect cells morphology and density; however, the scaffolds morphology was affected in some level. The fixation with osmium tetroxide interfered in the natural structure of cells and scaffold. In conclusion the freeze drying and glutaraldehyde are suitable methods for cell fixation in AH scaffold for SEM, although scaffolds structure seems to be affected by glutaraldehyde. Microsc. Res. Tech. 78:553–561, 2015. © 2015 Wiley Periodicals, Inc.     

Towards Heterogeneous and Green Versions of Os Dihydroxylation Catalysis

Os-catalyzed dihydroxylation will find more widespread application if truly heterogeneous catalysts are available which use O₂ or H₂O₂ as terminal oxidants. This paper discusses and critically evaluates the concepts by which Os can be anchored on solid supports. New methods are also available for reoxidation of hexavalent to octavalent Os.     

Carbonaceous fragments of osmium ligand deficient clusters that take part in alkane C-H and C-C bonds cleavage in the presence of molecular hydrogen

The direct participation of carbonaceous ligands of osmium ligand deficient clusters (LDC) in alkane and cycloalkane reactions in the presence of H₂ is proved by¹⁴C-labeling. In contrast to the other metallic catalysts, wherein carbonaceous ligands block active centres, the C-containing ligands of the Os-LDC are active and exhibit at least two functions in alkane and cycloalkane reactions: stabilization of clusters against agglomeration and preservation of active centres.Deceased on the 7th of January 1991.     

Rational Design of Charge‐Neutral,Near‐Infrared‐Emitting Osmium(II) Complexes and OLED Fabrication

A new series of charge neutral Os(II) isoquinolyl triazolate complexes ( 1 – 4 ) with both trans and cis arrangement of phosphine donors are synthesized, and their structural, electrochemical and photophysical properties are established. In sharp contrast to the cis‐arranged complexes 2 – 4 , the trans derivative 1 , which shows a planar arrangement of chromophoric N‐substituted chelates, offers the most effective extended π‐delocalization and hence the lowest excited state energy gap. These complexes exhibit phosphorescence with peak wavelengths ranging from 692–805 nm in degassed CH₂Cl₂ at room temperature. Near‐infrared (NIR)‐emitting electroluminescent devices employing 6 wt % of 1 (or 4 ) doped in Alq₃ host material are successfully fabricated. The devices incorporating 1 as NIR phosphor exhibit fairly intense emission with a peak wavelength at 814 nm. Forward radiant emittance reaches as high as 65.02 µW cm^?2, and a peak EQE of ～1.5% with devices employing Alq₃, TPBi and/or TAZ as electron‐transporting/exciton‐blocking layers. Upon switching to phosphor 4 , the electroluminescence blue shifts to 718 nm, while the maximum EQE and radiance increase to 2.7% and 93.26 (μW cm^?2) respectively. Their performances are optimized upon using TAZ as the electron transporting and exciton‐blocking material. The OLEDs characterized represent the only NIR‐emitting devices fabricated using charge‐neutral and volatile Os(II) phosphors via thermal vacuum deposition.     

Sharpless Asymmetric Dihydroxylation of Olefins in WaterSurfactant Media with Recycling of the Catalytic System by Membrane Nanofiltration

This paper presents a new and more sustainable alternative approach for the Sharpless catalytic asymmetric dihydroxylation (AD) of olefins using a water/surfactant system as reaction media. The AD reaction was performed using several cationic and anionic surfactants allowing yields and enantiomeric excesses higher or comparable with the conventional systems (using organic mixtures). The use of this water/surfactant medium offers the additional advantage of performing the reactions without the need of a slow addition of olefins. Asymmetric dihydroxylation of 1‐hexene in a 1.5 mM sodium cholate aqueous solution, using N‐methylmorpholine N‐oxide (NMO) as co‐oxidant was selected as model system to evaluate the feasibility of recycling the Sharpless catalytic system by nanofiltration. The reaction media was processed by nanofiltration, the product was isolated in the permeate, whereas the catalytic system and surfactant were retained by the membrane and recycled through six successive reactions, improving the catalyst turn‐over number. The experimental results were compared with the ones calculated on the basis of mass balances, membrane rejections to product and reaction yields.