Die Verbindungen des Phenylhydrazins mit den Zuckerarten

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Selective nucleation and growth of metal-organic open framework thin films on patterned COOH/CF3-terminated self-assembled monolayers on Au(111)

Metal-Organic open Framework coordination polymers (MOFs) are a fascinating class of materials. We demonstrate the selective growth of patterned thin films of MOF-5 and the subsequent loading with a palladium organic compound, which acts as a precursor for the deposition of palladium nanoclusters inside the cavities of the MOF-5 material.     

Directed evolution of the fatty-acid hydroxylase P450 BM-3 into an indole-hydroxylating catalyst

The self-sufficient cytochrome P450 BM-3 enzyme from Bacillus megaterium catalyzes subterminal hydroxylation of saturated long-chain fatty acids and structurally related compounds. Since the primary structure of P450 BM-3 is homologous to that of mammalian P450 type II, it represents an excellent model for this family of enzymes. During studies on the directed evolution of P450 BM-3 into a medium-chain fatty-acid hydroxylase, several mutants, in particular the triple mutant Phe87Val, Leu188Gln, Ala74Gly, were observed to hydroxylate indole, producing indigo and indirubin at a catalytic efficiency of 1365 M(-1)s(-1) (kcat=2.73 s(-1) and Km=2.0 mM). Both products were unequivocally characterized by NMR and MS analysis. Wild-type P450 BM-3 is incapable to hydroxylate indole. These results demonstrate that an enzyme can be engineered to catalyze the transformation of substrates with structures widely divergent from those of its native substrate.     

Chromatographic properties of the ion-exclusion column IonPac ICE-AS6 and its application in environmental analysis, Part II: application in environmental analysis

Biological processes, geochemical reactions, anthropogenic emissions, and transformation reactions of xenobiotics are responsible for the widespread occurrence of aliphatic carboxylic acids in the environment. To study the performance of the ion-exclusion chromatography column IonPac ICE-AS6 in the analysis of environmental and environmental-technical samples, organic acids are investigated in composting seepage, silage effluents, aqueous extracts of sewage sludge, molasses hydrolysate, and alkaline cellulose hydrolysates. With respect to the diverse sample matrix and composition, different chromatographic conditions are applied. It is possible to determine various volatile fatty acids, dicarboxylic acids, (poly)hydroxy acids, and keto acids as main and trace components in samples with very high and low dissolved organic carbon content. Low baseline noise allows the determination of malic and succinic acid in the concentration range of approximately 1 microM/L in the presence of higher concentrations of fully ionized compounds. The applicability of the column in environmental analysis may be limited by the poor retardation of strong organic acids, insufficient separation of some relevant substance combinations (i.e., citric and isocitric acid), and very strong hydrophobic interactions with straight-chain monocarboxylic acids containing four or more carbon atoms.     

Polymerization of Cyclic Monomers, 10,

Methyl 2‐(bicyclo[3.1.0]hex‐1‐yl)acrylate ( 1 ) was synthesized from methyl 2‐(cyclopentene‐1‐yl)‐2‐hydroxyacetate by cyclopropanation, followed by oxidation to the corresponding bicyclic 2‐oxoacetate and Wittig olefination with methyltriphenylphosphonium bromide. Initiated with 2,2′‐azoisobutyronitrile at 65 °C in chlorobenzene, the radical homopolymerization of 1 occurred with opening of the cyclopropane ring leading to a polymer with a glass transition temperature of 90 °C. The reactivity of 1 in radical copolymerization was higher than that of methyl methacrylate.

     

Stereoselective aza-Diels-Alder reactions with 2H-azirines as dienophiles furnishing highly functionalized tetrahydropyridines

Highly diastereoselective Lewis acid mediated aza-Diels-Alder reactions of chiral auxiliary derivatized 2H-azirines have been accomplished for the first time, yielding bi and tri-cyclic heterocyclic compounds, comprising aziridine and tetrahydropyridine substructures, in up to 97% de; with the absolute stereochemistry of the major product confirmed by X-ray crystallography.