Intramolecular cyclization mediated by silylmetalation of acetylenes with PhMe2SiMgMe/CuI and radical nature of the reagent

Whereas CuI catalyzed silylmagnesation of the tosylate of 5- hexyn-l-ol with the title reagent affords dimethylphenylsilylmethylenecyclopentane exclusively, the mesylate of 3-butyn-l-ol gives a mixture of unexpected silylcyclobutene and cyclopropylidene derivative.     

Reduction behavior of Ru/CeO2 catalysts and their activity for wet oxidation

Three kinds of Ru/CeO₂ catalysts were prepared. The mobility of the oxygen on Ru and their catalytic activity in the wet oxidation of acetic acid was investigated. Ru was present in the form of RuO₂, and TPR experiment showed that the reaction, RuO₂ + 2H₂ Ru + 2H₂O, took place in different temperature ranges depending upon the kind of the catalysts. The catalyst with easily reducible oxygen on Ru had high activity in wet oxidation, and the importance of the release of oxygen from Ru to the reactant was suggested.     

Regioselective stannylmetalation of acetylenes in the presence of transition-metal catalyst

The reaction of terminal acetylenes with Bu₃SnMgMe, Bu₃SnA1Et₂, or (Bu₃Sn)₂Zn in the presence of various transition-metal catalysts provides vinylstannanes in good yields. Whereas copper catalysed stannylmagnesation of 4-benzyloxy-1-butyne gives (E)-4-benzyloxy-1-tributylstannyl-1-butene exclusively, palladium catalysed stannylzincation affords 4-benzyloxy-2-tributylstannyl-1-butene preferentially.     

Explicitly correlated second order perturbation theory: introduction of a rational generator and numerical quadratures

A rational generator, which fulfills the cusp conditions for singlet and triplet electron pairs, is proposed and applied to explicitly correlated second order M?ller-Plesset perturbation theory calculations. It is shown that the generator in conjunction with frozen geminals improves the convergence of correlation energy without introducing any variational parameters in explicitly correlated functions. A new scheme for three-electron integrals based on numerical quadratures is also illustrated. The method is tested for the convergence of reaction enthalpies with various basis sets.     

Diffusion coefficients of metal acetylacetonates in supercritical carbon dioxide

Binary diffusion coefficients, D₁₂, of the metal acetylacetonates, palladium(II) acetylacetonate and cobalt(III) acetylacetonate, were measured from 308.2 to 343.2 K over the pressure range from 9 to 40 MPa at infinite dilution in supercritical carbon dioxide using the chromatographic impulse response method. The effects of pressure, temperature, density, and viscosity on D₁₂ values were examined. It was observed that the D₁₂ values of palladium(II) acetylacetonate and cobalt(III) acetylacetonate were larger than those of lipids with similar molecular weights, such as arachidonic acid and monoolein, respectively. Furthermore, the measured D₁₂ data of each metal acetylacetonate were well correlated by the hydrodynamic equation D₁₂/T as a function of carbon dioxide viscosity.     

Enzyme-catalyzed resolution of 3,8-dioxatricyclo[3.2.1.0]octane-6-carboxylic esters and the application to the synthesis of 3-epishikimic acid

3,8-Dioxatricyclo[3.2.1.0^2,4]octane-6-carboxylic acid, whose racemic form is readily available on a large scale, is a versatile starting material for the synthesis of carbasugars and carbocyclic biologically active natural products. In this study, the enzyme-catalyzed kinetic resolution was attempted on a variety of corresponding carboxylic esters. The hydrophobic and hydrophilic properties of ester substituents greatly affected the rate of reaction and the enantioselectivity. Hydrolysis of the corresponding 2′-chloroethyl ester with pig liver esterase worked well in a highly enantioselective manner (E = 116) to give the hydrolyzate (90.6% ee) and unreacted ester recovery (99.4% ee). The hydrolyzate is a precursor for (−)-oseltamivir phosphate, and a route to (3S,4S,5R)-(−)-3-epishikimic acid was developed from the recovered ester.     

Preferential 5‐Methylcytosine Oxidation in the Linker Region of Reconstituted Positioned Nucleosomes by Tet1 Protein

Tet (ten–eleven translocation) family proteins oxidize 5‐methylcytosine (mC) to 5‐hydroxymethylcytosine (hmC), 5‐formylcytosine (fC), and 5‐carboxycytosine (caC), and are suggested to be involved in the active DNA demethylation pathway. In this study, we reconstituted positioned mononucleosomes using CpG‐methylated 382 bp DNA containing the Widom 601 sequence and recombinant histone octamer, and subjected the nucleosome to treatment with Tet1 protein. The sites of oxidized methylcytosine were identified by bisulfite sequencing. We found that, for the oxidation reaction, Tet1 protein prefers mCs located in the linker region of the nucleosome compared with those located in the core region.     

Modification of interlayer space of kanemite with trimethylsilyl groups: structure and adsorption properties

Interlayer hydroxyl groups of layered silicate kanemite have been modified with trimethylsilyl groups by the reaction between the hydroxyl groups and trimethylchlorosilane. Expansion of the interlayer space by intercalation of dimethyldialkylammonium ions into the silicate layers enables the silylating reagent to access the hydroxyl groups. An increase in specific surface areas was observed with increasing concentration of trimethylsilyl groups. This result suggests that the interlayer space of kanemite can be used as an effective molecular adsorption space by weakening the interaction between the interlayer hydrogen bonds of hydroxyl groups. The modification of kanemite with trimethylsilyl groups restricted the adsorption of water below a monolayer capacity and was favorable for benzene adsorption.