Three-dimensional snow images by MR microscopy

MR microscopy technique was introduced to visualize and quantify the three-dimensional structure of snowpack. Since the NMR signal from the ice was week, we looked at the air space instead filling with dodecane or aniline doped with iron acetylacetonate. Four types of snow were tested: ice spheres, large rounded poly crystals, small rounded mono-crystals and depth hoar crystals. A specific specimen-cooling system was developed to keep the temperature below 0 degrees C. In the experiments 0.5 to 2 h were necessary to accumulate the signals enough to obtain a 3D micro-image; the image matrix 128(3), voxel size (200 microm)3 or 256(3) (120 microm)3. Comparison with the 2D data using the conventional section plane method was also carried out and MR microscopy is proved to be a very useful method to visualize the microstructure of snowpack.     

Rhenium-catalyzed regioselective synthesis of multisubstituted pyridines from β-enamino ketones and alkynes via C-C bond cleavage

A new method is described for the regioselective synthesis of multisubstituted pyridine derivatives. Treatment of N-acetyl β-enamino ketones with alkynes in the presence of the rhenium catalyst, Re(2)(CO)(10), gives multisubstituted pyridines regioselectively. In this reaction, the N-acetyl moieties are important for the selective formation of the multisubstituted pyridines. This reaction proceeds via insertion of alkynes into a carbon-carbon single bond of β-enamino ketones, intramolecular nucleophilic cyclization, and elimination of acetic acid.     

Preparation of mesoporous silicas using food grade emulsifiers and its application for enzyme supports

A novel mesoporous silica (TMPS) was synthesized via self-assembly using a myristic acid ester of pentaglycerol. The ester is obtained from catalytic esterification and it is commercially available as a food grade emulsifier. TMPS material was employed for preparation of a biocatalyst in order to examine the ability as an enzyme support in comparison with the other mesoporous silica materials having a channel or a cage-like pore system. The used TMPS materials possessed the interconnected channel-like pore system with the pore sizes of 9.2, 12, and 16 nm. The materials successfully entrapped lipase into their mesopores with the high loadings. The resultant lipase/TMPS conjugates functioned as the biocatalyst for hydrolysis of p-nitrophenyl propionate (p-NPP), having the higher activity than those of the used mesoporous silica conjugates. The high activities were ascribed to the textural properties such as the small particle length, large pore size and the three-dimensional pore connectivity that permit the accessibility of p-NPP to the immobilized lipases during the reactions. Consequently, we concluded that TMPS materials are of the suitable mesoporous support for the enzymes.     

Direct Observation of Fluorescently Labeled Single-stranded λDNA Molecules in a Micro-Flow Channel

We developed two labeling methods for the direct observation of single-stranded DNA (ssDNA), using a ssDNA binding protein and a ssDNA recognition peptide. The first approach involved protein fusion between the 70-kDa ssDNA-binding domain of replication protein A and enhanced yellow fluorescent protein (RPA-YFP). The second method used the ssDNA binding peptide of Escherichia coli RecA labeled with Atto488 (ssBP-488; Atto488-IRMKIGVMFGNPETTTGGNALKFY). The labeled ssλDNA molecules were visualized over time in micro-flow channels. We report substantially different dynamics between these two labeling methods. When ssλDNA molecules were labeled with RPA-YFP, terminally bound fusion proteins were sheared from the free ends of the ssλDNA molecules unless 25-mer oligonucleotides were annealed to the free ends. RPA-YFP-ssλDNA complexes were dissociated by the addition of 0.2 M NaCl, although complex reassembly was possible with injection of additional RPA-YFP. In contrast to the flexible dynamics of RPA-YFP-ssλDNA complexes, the ssBP-488-ssλDNA complexes behaved as rigid rods and were not dissociated even in 2 M NaCl.     

Differential geometry of edgeworth expansions in curved exponential family

Summary In order to construct a higher-order asymptotic theory of statistical inference, it is useful to know the Edgeworth expansions of the distributions of related statistics. Based on the differential-geometrical method, the Edgeworth expansions are performed up to the third-order terms for the joint distribution of any efficient estimators and complementary (approximate) ancillary statistics in the case of curved exponential family. The marginal and conditional distributions are also obtained. The roles and meanings of geometrical quantities are elucidated by the geometrical interpretation of the Edgeworth expansions. The results of the present paper provide an indispensable tool for constructing the differential-geometrical theory of statistics.     

Catalytic asymmetric synthesis of binaphthol derivatives by aerobic oxidative coupling of 3-hydroxy-2-naphthoates with chiral diamine-copper complex

Asymmetric aerobic oxidative coupling of 3-hydroxy-2-naphthoate with a copper complex prepared in situ from chiral diamine 3 and cuprous chloride as catalyst afforded binaphthol derivatives in good enantioselectivities up to 73% ee.     

Lewis acidity/basicity of pi-electron systems: theoretical study of a molecular interaction between a pi system and a Lewis acid/base

Molecular interactions between pi systems having different pi-electron character (benzene, hexafluorobenzene, and borazine), and a Lewis acid/base (borane and ammonia) were theoretically studied. An attractive interaction between benzene, the electron-rich pi system, and borane was observed. On the other hand, repulsive interactions between benzene and ammonia was observed when the lone pair of nitrogen points toward the benzene ring. In contrast, an attractive interaction between hexafluorobenzene, an electron-deficient pi system, and ammonia was observed. Unexpectedly, a weak attractive interaction between hexafluorobenzene and borane was also observed. Borazine shows an interaction both to borane and ammonia. The attraction between the nitrogen atom of borazine and borane was larger than that between the boron atom of borazine and ammonia.     

9-Acylation of 1-acyldipyrromethanes containing a dialkylboron mask for the alpha-acylpyrrole motif

1,9-Diacyldipyrromethanes are important precursors to porphyrins, yet synthetic access remains limited owing to (1) poor conversion in the 9-acylation of 1-acyldipyrromethanes and (2) handling difficulties because acyldipyrromethanes typically streak upon chromatography and give amorphous powders upon attempted crystallization. A reliable means for converting a dipyrromethane to a 1-acyldipyrromethane-dialkylboron complex was recently developed, where the dialkylboron (BR(2)) unit renders the complex hydrophobic and thereby facilitates isolation. Herein a refined preparation of 1,9-diacyldipyrromethanes is presented that employs the 1-acyldipyrromethane-BR(2) complex as a substrate for 9-acylation. The dialkylboron unit provides protection for the alpha-acylpyrrole unit. 9-Acylation requires formation of the pyrrolyl-MgBr reagent and the presence of 1 equiv of a nonnucleophilic base to quench the proton liberated upon alpha-acylation. Reaction of the 1-acyldipyrromethane-BR(2) complex (1 equiv) with mesitylmagnesium bromide (2 equiv) followed by the addition of an acylating agent (S-2-pyridyl thioate or acid chloride, 1.1 equiv) gives the corresponding 1,9-diacyldipyrromethane-BR(2) complex. The acylation method afforded 1,9-diacyldipyrromethane-BR(2) complexes with limited or no chromatography in yields of 64-92%. The 1,9-diacyldipyrromethane-BR(2) complexes are stable to routine handling, are readily soluble in common organic solvents, crystallize readily, and can now be prepared in multigram quantities through use of stoichiometric quantities of reagents.     

A tin-complexation strategy for use with diverse acylation methods in the preparation of 1,9-diacyldipyrromethanes

The acylation of dipyrromethanes to form 1,9-diacyldipyrromethanes is an essential step in the rational synthesis of porphyrins. Although several methods for acylation are available, purification is difficult because 1,9-diacyldipyrromethanes typically streak extensively upon chromatography and give amorphous powders upon attempted crystallization. A solution to this problem has been achieved by reacting the 1,9-diacyldipyrromethane with Bu(2)SnCl(2) to give the corresponding dibutyl(5,10-dihydrodipyrrinato)tin(IV) complex. The reaction is selective for dipyrromethanes that bear acyl groups at both the 1- and 9-positions but otherwise is quite tolerant of diverse substituents. The diacyldipyrromethane-tin complexes are stable to air and water, are highly soluble in common organic solvents, crystallize readily, and chromatograph without streaking. Four methods (Friedel-Crafts, Grignard, Vilsmeier, benzoxathiolium salt) were examined for the direct 1,9-diacylation of a dipyrromethane or the 9-acylation of a 1-acyldipyrromethane. In each case, treatment of the crude reaction mixture with Bu(2)SnCl(2) and TEA at room temperature enabled facile isolation of multigram quantities of the 1,9-diacyldipyrromethane-tin complex. The diacyldipyrromethane-tin complexes could be decomplexed with TFA in nearly quantitative yield. Alternatively, use of a diacyldipyrromethane-tin complex in a porphyrin-forming reaction (reduction with NaBH(4), acid-catalyzed condensation with a dipyrromethane, DDQ oxidation) afforded the desired free base porphyrin in yield comparable to that obtained from the uncomplexed diacyldipyrromethane. The acylation/tin-complexation strategy has been applied to a bis(dipyrromethane) and a porphyrin-dipyrromethane. In summary, the tin-complexation strategy has broad scope, is compatible with diverse acylation methods, and greatly facilitates access to 1,9-diacyldipyrromethanes.