Ageladine A: an antiangiogenic matrixmetalloproteinase inhibitor from the marine sponge Agelas nakamurai

A novel MMP inhibitor, ageladine A (1) with antiangiogenic activity was isolated from a marine sponge Agelas nakamurai. Structure 1 was determined by a combination of spectroscopic and chemical methods to be an unprecedented structure of 4-(4,5-dibromo-1H-pyrrol-2-yl)]-1H-imidazo[4,5-c]pyridin-2-amine.     

Rigid-rod polymers with polysiloxane side chains. 2. Synthesis and characterization of aromatic polybenzobisoxazoles with polysiloxane side chains and composite formation with polysiloxane matrices

Aromatic polybenzobisoxazoles, having polydimethylsiloxane side chains (SCPBOs), were prepared using terephthaloyl chloride-terminated polydimethylsiloxane macromonomers and 3,3′-bis(trimethylsiloxy)-4,4′-bis(trimethylsilylamino)biphenyl for the purpose of dispersing rigid-rod molecules in silicone matrices for molecular reinforcement. The degree of polymerization of the side chain was varied from 7.8 to 45.4, and a small amount of (3-butenyloxy)terephthaloyl chloride was copolymerized to give the polymers a functionality that can be linked to the matrices. For all the SCPBOs, the WAXD pattern showed only diffuse reflections, suggesting limited structural regularity, although the polymers were optically anisotropic. No melting transition was observed below the side chain decomposition temperature, 350°C. A polydimethylsiloxane/polybenzobisoxazole composite elastomer was obtained first curing the polysiloxane matrix containing the prepolymer of the SCPBO, followed by in situ thermal ring closure of the prepolymer. Some reinforcement was observed, but the presence of plasticizing effect by the unbound SCPBO was suggested at the same time. © 1995 John Wiley & Sons, Inc.     

Effect of labile hydrogens on measurement of tritium preserved in hydrogens of cellulose

Various f-elements are separated as anionic complexes from both acidic and alkaline solutions by precipitation with alkylpyridinium salts. The precipitates are also cationic surfactants where the simple counter-ion (e.g. nitrate or chloride) is replaced by the negatively charged complex anion of an actinide or lanthanide. The low solubility of these precipitates is explained by a strong affinity of divalent complex counter-ions of f-elements to the quaternary nitrogen. Precipitations in solutions of nitric acid allow to separate tetravalent f-elements from other metals, in alkaline carbonate solutions tetravalent and hexavalent actinides are precipitated simultaneously. The last procedure yields precipitates, which are very intimate mixtures of hexavalent and tetravalent actinides. This allows to prepare mixed oxides in a simple way.     

First linear alignment of five C-Se...O...Se-C atoms in anthraquinone and 9-(methoxy)anthracene bearing phenylselanyl groups at 1,8-positions

Five Ci-Se...O...Se-Ci atoms in anthraquinone and 9-(methoxy)anthracene bearing phenylselanyl groups at 1,8-positions align linearly, the origin of which is shown to be a nonbonded 5c-6e interaction of the five atoms.     

A High Sensitivity Fluorescent Chemo-sensory System Based on β-Cyclodextrin Dimer Modified with Dansyl Moieties

-Cyclodextrin dimer linked with ethylenediamine at the upper rim of the cyclodextrin has been synthesized and then modified with two dansyl moieties inthe presence of N,N'-dicyclohexylcarbodiimide. The sensing ability and bindingproperty of the title compound were investigated for steroids and terpenoids. Thefluorescence intensity of this dimer was decreased when a host–guest complex was formed. The value I/I⁰, where I⁰ and I are fluorescence intensitiesin the absence and presence of a guest and I is I⁰- I, was used as a parameter of sensitivity. This host exhibited a much higher sensitivity and selective molecular recognition ability for bile acids such as ursodeoxycholic acid andchenodeoxycholic acid and terpenoids such as (-)-borneol than the dansyl-modifiedcyclodextrins reported previously including -cyclodextrin dimer. The behaviors of the appended moieties of the host during the formation of host–guest complexes were studied using induced circular dichroism (ICD) and fluorescence spectra. The ICD intensityof this dimer was decreased on accommodation of a guest and this spectral pattern of the title dimer was opposite to that of bis dansyl-modified -cyclodextrin monomer. Theguest-induced variations in the fluorescence and ICD intensities suggest that this dimer formed a 1 : 1 host–guest complex and the appended moieties act as a hydrophobic cap.     

Facile radical trifluoromethylation of lithium enolates

[reaction: see text] Highly basic lithium enolates are shown to be applicable to radical trifluoromethylation. The reaction is extremely fast, and the minimum reaction time is approximately 1 s.