Thermal and combustion characteristics of phosphorus and phosphorus/nitrogen-containing styrene monomers and oligomers

Two series of styrene monomers, one with phosphorus-containing moieties as substituents and the other with substituents containing both phosphorus and nitrogen, have been prepared, characterized, and converted to oligomers. The oligomers contain, in the one case, phosphorus and, in the other, phosphorus and nitrogen. This provides the opportunity to not only assess the impact of the presence of phosphorus on the combustion characteristics of the oligomers but to determine whether or not this impact is enhanced by the presence of nitrogen. The level of residue from thermogravimetry and heat release rate during combustion suggest that the presence of nitrogen may have a small positive impact on the effectiveness of phosphorus flame retardants.     

Development of Non-Hydrolysable Oligosaccharide Activity-Based Inactivators for Endoglycanases: A Case Study on α-1,6 Mannanases

There is a vast genomic resource for enzymes active on carbohydrates. Lagging far behind, however, are functional chemical tools for the rapid characterization of carbohydrate-active enzymes. Activity-based probes (ABPs) offer one chemical solution to these issues with ABPs based upon cyclophellitol epoxide and aziridine covalent and irreversible inhibitors representing a potent and widespread approach. Such inhibitors for enzymes active on polysaccharides are potentially limited by the requirement for several glycosidic bonds, themselves substrates for the enzyme targets. Here, it is shown that non-hydrolysable trisaccharide can be synthesized and applied even to enzymes with challenging subsite requirements. It was found that incorporation of carbasugar moieties, which was accomplished by cuprate-assisted regioselective trans-diaxial epoxide opening of carba-mannal synthesised for this purpose, yields inactivators that act as powerful activity-based inhibitors for α-1,6 endo-mannanases. 3-D structures at 1.35–1.47 Å resolutions confirm the design rationale and binding to the enzymatic nucleophile. Carbasugar oligosaccharide cyclophellitols offer a powerful new approach for the design of robust endoglycosidase inhibitors, while the synthesis procedures presented here should allow adaptation towards activity-based endoglycosidase probes as well as configurational isosteres targeting other endoglycosidase families.     

A Vertex Formalism for Local Ruled Surfaces

We develop a vertex formalism for topological string amplitudes on ruled surfaces with an arbitrary number of reducible fibers embedded in a Calabi-Yau threefold. Our construction is based on large N duality and localization with respect to a degenerate torus action. We also discuss potential generalizations of our formalism to a broader class of Calabi-Yau threefolds using the same underlying principles.     

Thermal behaviour of <Emphasis Type="Italic">sym</Emphasis>-octahydroacridines and their corresponding N(10)-oxides

We present and discuss results on the thermal behaviour of 1,2,3,4,5,6,7,8-octahydroacridine (OHA), together with six 9-substituted congeners, i.e. R = –Br, –OCH₃, –NH₂, –NO₂, –OH, and furyl (–C₄H₃O), and their corresponding N(10)-oxides, under nitrogen atmosphere and with alumina as reference, at a heating rate of 5 °C min^?1 from room temperature to 300 °C. Chromatography has been carried out on aluminium sheets, with aluminium oxide 60 F254 neutral (Merck). Melting effects are observed for almost all compounds in their corresponding curves, precisely determined by using a Boetius apparatus. Homolysis of the carbon-substituent bond occurs in most cases, a phenomenon which is consistent with the values of the bond dissociation energy. For all compounds, except for hydroxyl congeners, thermal decomposition started with an endothermic peak. Octahydroacridines readily decompose into volatile products, an effect which correlates with their low melting points, while little amounts of residue remain in place of the aromatic amines compared to the N(10)-oxides. The presence of N–O bonds greatly influences the thermal stability of the compound, in the sense of increasing it compared with the parent amine. Quantitative studies of the decomposition products reveal that the melting points, the 9-position substituent, and N–O bond all play an important role upon the thermal behaviour. Mechanistic/kinetic pathways are also proposed as such results are important in further designing laser processing protocols, i.e. matrix-assisted pulsed laser evaporation (MAPLE) or laser-induced forward transfer (LIFT), for thin film deposition and/or device printing.     

Electrochemical detection and removal of pharmaceuticals in waste waters

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Recherches dans la série des cyclitols XLVI. Actions de diazoalcanes sur la pentahydroxy-2,4,6/3,5-cyclohexanone et sur son dérivé penta-O-acétylé II. Etude de pentahydroxy-alkyl-C-cycloheptanones

On treatment with higher diazoalkanes, 2,4,6/3,5-penta-acetoxy-cyclohexanone (penta-O-acetyl-myo-inosose-2 or -scyllo-inosose) afforded by ring expansion all-trans-penta-acetoxy-C-alkyl-cycloheptanones, which by deacylation were converted to hemiacetals. The reactions with diazoalkanes of the penta-acetoxy-inosose in the presence of aluminium chloride and of the free inosose in water solution have also been studied. The structure, the configuration, and, in some cases, the conformation of the new compounds have been established and some of their reactions have been investigated. The mechanisms of formation of the ring expansion products and of the concomitant spiro-epoxides have been discussed.     

Nitrate esters as nitric oxide donors: SS-nitrates

[structure: see text]. The important biological secondary messenger NO can be generated from exogenous nitrovasodilators and NO donors. Nitrate esters are nitrovasodilators and NO mimetics, believed to be biotransformed to NO in vivo. On the basis of a mechanistic hypothesis, nitrates have been synthesized that release NO at significant rates in neutral aqueous solution in the presence only of added thiol. The novel masked beta-mercaptonitrates reported (SS-nitrates), provide information on possible sulfhydryl-dependent biotransformation mechanisms for nitrates in clinical use.     

A Novel Approach for the Synthesis of 5‐Pyridylindolizine Derivatives via 2‐(2‐Pyridyl)pyridinium Ylides

New indolizine derivatives were synthesized by an efficient one‐pot three‐component procedure starting from commercially available materials such as 2,2′‐dipyridyl, substituted bromoacetophenones, and electron‐poor alkynes in 1,2‐epoxybutane as reaction solvent and acid scavenger.