UV-Vis spectroscopic study on effects of pressure for adsorption ofp-nitrotoluene at liquid-solid interface

The behavior ofp-nitrotoluene adsorbed at zeolite/n-heptane interface has been investigated by the electronic spectroscopy under pressure up to 300 MPa. The uv-vis absorption bands of adsorbedp-nitrotoluene were deconvoluted into ones for the species adsorbed on the cation sites, and one for that on the pore wall of zeolite. The peak of adsorbed species on the cation site red-shifted by 20–80 nm from the position of the same species in the liquid phase, and their magnitudes of shift depended on the strength of electric field generated by the cation in zeolites. The peak intensities of adsorbed species on the cation site were enhanced but these or the pore wall site were reduced with the increase in pressure, suggesting that a part ofp-nitroluene molecules on the pore wall site desorbed and the adsorption on the cation site was enhanced by compression. The pressure dependence of peak intensity indicated that the behavior of this adsorption system was strongly governed by the solvation structure of the adsorbate in the zeolite pore. In particular, it was found that the adsorption of solvent molecules on the cation site strongly affected the volume change of the adsorption system.     

Improvement of Nitrogen Supply for L-Threonine Production by a Recombinant Strain of Serratia marcescens

Serratia marcescens T-2000 was previously reported to be an l-threonine-producing strain that harbors the recombinant plasmid carrying the mutant-type threonine operon. This strain produced 55 g of l-threonine/L of the medium containing urea as a nitrogen source after 72 h of cultivation. In the urea-containing medium, transitory stop of the growth was observed during the early period of cultivation when the entire amount of ammonium ion formed from urea via heat decomposition disappeared in the medium. This indicated that the shortage of ammonium supply in cells might delay both the cell growth and the l-threonine production. The use of ammonia water as a nitrogen source for l-threonine production was therefore studied, because microbial cells generally assimilate this source more readily than urea. When ammonia water was automatically fed to the medium so as to maintain the pH of the medium at around 7, the growth was accelerated, and the l-threonine production reached a maximum of 65 g/L at 48 h. Under these conditions, sucrose, a carbon source, was continuously fed to the medium, resulting in the production of 100 g of l-threonine/L at 96 h. Thus, the l-threonine productivity of the recombinant l-threonine-producing strain could be increased by devising the method for supply of a nitrogen source.     

Stereoselective synthesis of methyl (Z)-(4,4-difluoro-2,3,4,5-tetrahydro-1H-1-benzazepin-5-ylidene)acetate using a dianion Horner-Wadsworth-Emmons reagent

Stereoselective synthesis of methyl (Z)-(4,4-difluoro-2,3,4,5-tetrahydro-1H-1-benzazepin-5-ylidene)acetate (1a) is described. Z-selectivity of the Horner-Wadsworth-Emmons (HWE) reaction was obtained based on an investigation of the reaction conditions for introduction of a methylidene group onto the 5-position of benzazepine.     

Catalytic asymmetric cyano-ethoxycarbonylation reaction of aldehydes using a YLi3 tris(binaphthoxide) (YLB) complex: mechanism and roles of achiral additives

Full details of a catalytic asymmetric cyano-ethoxycarbonylation reaction promoted by a heterobimetallic YLi3 tris(binaphthoxide) complex (YLB 1), especially mechanistic studies, are described. In the cyanation reaction of aldehydes with ethyl cyanoformate, three achiral additives, H2O, tris(2,6-dimethoxyphenyl)phosphine oxide (3a), and BuLi, were required to achieve high reactivity and enantioselectivity (up to >99% yield and up to 98% ee). The roles of achiral additives and the reaction pathway were investigated in detail. In situ IR analysis revealed that the initiation step to generate LiCN from H2O, BuLi, and ethyl cyanoformate is rather slow. On the basis of mechanistic studies of the initiation step to generate an active nucleophilic species, reaction conditions were optimized by using a catalytic amount of acetone cyanohydrin as an initiator. Under the optimized conditions, the induction period decreased and the reaction completed within 9 min using 5 mol % YLB at -78 degrees C. Catalyst loading was successfully reduced to 1 mol %. Kinetic experiments and evaluation of the substituent effects of phosphine oxide revealed that phosphine oxide had beneficial effects on both the reaction rate and the enantioselectivity. The putative active species as well as the catalytic cycle of the reaction are also discussed.     

Red luminescence in MgO-GeO<Subscript>2</Subscript> gel glasses and glass ceramics doped with Mn ions prepared by sol-gel method

To obtain red luminants, MgO-GeO₂ gel glasses and glass ceramics doped with manganese ions were prepared by a sol-gel method and their properties were investigated by measuring X-ray diffraction (XRD), electron spin resonance (ESR), and luminescence and excitation spectra. Under UV irradiation at 254 nm, the gel glasses and glass ceramics showed red luminescence at 620–665 nm, the intensity of which became strong with increasing the heat-treatment temperature. A glass ceramic with the composition 1.0MnO-25MgO-75GeO₂ heat treated at 1000°C exhibited the strongest red luminescence at 661 nm. From the results of XRD and ESR, this luminescence is found to be due to the transition from the ⁴T_1g to the ⁶A_1g state of octahedrally coordinated Mn²⁺ ions located in MgGeO₃ polycrystals. The luminescence wavelength of the glass ceramics (∼665 nm) is long compared with Eu³⁺-containing phosphors (612 nm), therefore the glass ceramics can be expected for red luminants.     

Michael addition of stannyl ketone enolate to alpha,beta-unsaturated esters catalyzed by tetrabutylammonium bromide and an ab initio theoretical study of the reaction course

Michael addition of stannyl ketone enolates to alpha,beta-unsaturated esters was accomplished in the presence of a catalytic amount of tetrabutylammonium bromide (Bu(4)NBr). Other typical systems using lithium enolate or silyl enolate with catalysts (TiCl(4) or Bu(4)NF) failed to give the desired products. The bromide anion from Bu(4)NBr coordinates to the tin center in enolate to accelerate the conjugate addition where a five-coordinated tin species was generated. The coordination of the bromide anion significantly raises the HOMO level of tin enolate and enhances its nucleophilicity. The conjugate addition provides the intermediate Michael adduct, which has an ester enolate moiety, and the adduct immediately transforms to alpha-stannyl gamma-ketoester by keto-enol tautomerization. This step contributes to the stabilization of the product system and leads to a thermodynamically favorable reaction course. An ab initio calculation reveals that the activation energy in the reaction using the bromide anion is lower than that of the reaction without using it. The transition state in either reaction course has a linear structure, not a cyclic one. This system can be applied to a variety of tin enolates and alpha,beta-unsaturated carbonyls involving enoates, enones, and unsaturated amides.     

Bismuth‐ and Hafnium‐Catalyzed Hydroamination of Vinyl Arenes with Sulfonamides,Carbamates, and Carboxamides

Catalytic intermolecular hydroamination of vinyl arenes is described. Our initial investigation revealed that a Bi(OTf)₃/[Cu(CH₃CN)₄]PF₆ system previously developed for catalytic intermolecular hydroamination of 1,3‐dienes was suitable for hydroamination of a styrene with sulfonamides, but the substrate generality of this system was unsatisfactory. Several metals were screened to expand the substrate scope, and a new Hf(OTf)₄/[Cu(CH₃CN)₄]PF₆ system was determined to be highly suitable. The combination of Hf(OTf)₄ and [Cu(CH₃CN)₄]PF₆ efficiently promoted the hydroamination of various vinyl arenes, including less‐reactive vinyl arenes with electron‐withdrawing groups. This strategy was applied to sulfonamides, carbamates, and carboxamides, and products were obtained in up to 99 % yield with 0.3–10 mol % catalyst loading.     

Regulated interaction between polypeptide chain elongation factor-1 complex with the 26S proteasome during <Emphasis Type="Italic">Xenopus</Emphasis> oocyte maturation

Background  

During Xenopusoocyte maturation, the amount of a 48 kDa protein detected in the 26S proteasome fraction (p48) decreased markedly during oocyte maturation to the low levels seen in unfertilized eggs. The results indicate that the interaction of at least one protein with the 26S proteasome changes during oocyte maturation and early development. An alteration in proteasome function may be important for the regulation of developmental events, such as the rapid cell cycle, in the early embryo. In this study, we identified p48.     

Syntheses of 10-oxo, 10 alpha-hydroxy, and 10 beta-hydroxy derivatives of a potent kappa-opioid receptor agonist, TRK-820

Syntheses of 10-oxo, 10alpha-hydroxy, and 10beta-hydroxy derivatives of a potent kappa-opioid receptor selective agonist, TRK-820, are described. These derivatives were supposed to be potential degradation products in formulation of TRK-820 as a result of autoxidation. 10-Oxo-TRK-820 11 was derived from 10-oxo-4,5-epoxymorphinan 14 in 10 steps in 32% overall yield. Reduction of the 10-oxo group in 4,5-epoxymorphinan with NaBH(4) gave 10beta-hydroxy-4,5-epoxymorphinan, exclusively. A stepwise inversion method of the 10beta-hydroxy group to produce 10alpha-hydroxy-4,5-epoxymorphinan was established. By HPLC analyses, 10alpha-hydroxy-TRK-820 12 was confirmed to be one of the degradation products in developing formulation of TRK-820.     

Electrochemical approach to evaluate the mechanism of photocatalytic water splitting on oxide photocatalysts

Photoelectrochemical measurements of TiO₂, NaTaO₃, and Cr or Sb doped TiO₂ and SrTiO₃ photocatalysts were carried out in H₂ and O₂ saturated electrolytes in order to evaluate the reverse reactions during water photolysis. The poor activity of TiO₂ as a result of reverse photoreactions of O₂ reduction and H₂ oxidation was revealed with the respective high cathodic and anodic photocurrents. The rise in the photocurrents at NaTaO₃ after La doping was in harmony with the doping-induced increase in the photocatalytic activity. NiO loading suppresses the O₂ photoreverse reactions, which declines photocatalytic activity, and/or promotes the photo-oxidation of water, because the O₂ photo-reduction current was scarcely observed near the flatband potential. Photocurrents of O₂ reduction and H₂ oxidation were observed under visible light for the Cr and Sb doped SrTiO₃ and TiO₂, respectively. These phenomena are in harmony with the previous reports on the photocatalysts examined with sacrificial reagents.