Studies on the thermal decomposition of phthalate esters: IX. Thermal decomposition of bis(2-ethylhexyl) phthalate

A flow apparatus equipped with a spray nozzle was developed for investigating the thermal decomposition of esters with high boiling points and viscosities. The thermal decomposition of bis(2-ethylhexyl) phthalate (BEHP), which is a typical plasticizer for poly(vinyl chloride) with a high boiling point and viscosity, was carried out by the use of the flow apparatus. The thermal decomposition products were analysed by gas chromatography and the kinetic parameters were calculated. The kinetic parameter of bis(2-ethylhexyl) phthalate was k_BEHP (s^?1)=4.59·10¹¹ exp(?40600/RT). From a comparison with the values for phthalic esters, it is proposed that a cis-elimination reaction takes place with a two-step mechanism in which the rate-determining step is α-carbon cleavage.     

Enantioselective synthesis of heliannuol E; structural consideration of natural molecule

Heliannuol E 1, isolated from Helianthus annuus L. cv. SH-222, was successfully synthesized in both optically active forms, by novel ring-expansion reaction of the corresponding spirodienone derivatives 8 and 17, which were produced from 7 and 16 under anodic oxidation conditions. The absolute structure of the natural product was determined to have R-configuration at the benzylic position.     

Photochemistry of Flavins in Micelles: Specific Effects of Anionic Surfactants on the Monomerization of Thymine Cyclobutane Dimers Photosensitized by Tetra-O-acyl Riboflavins*

It was found that tetra-o-acyl riboflavins efficiently photosensitize the monomerization of the cis, syn-cyclobutane dimers of 1,3-dimethylthymine and 1,3-dimethyluracil in aqueous solution in the presence of such anionic surfactants as sodium dodecyl sulfate and sodium hexadecyl sulfate at concentrations higher than their critical micelle concentration, while little monomerization of the dimers was photosensitized by the flavins in the absence of the surfactants and even in the presence of cationic and nonionic surfactants.     

Stereoselective total synthesis of ( + )-brefeldin A

A total synthesis of ( + )-brefeldin A, an antibiotic fungal metabolite, has been achieved stereoselectively starting from ( + )-mannitol and ( + )-glutamic acid.     

Determination of fluoxetine and norfluoxetine in rat brain microdialysis samples following intraperitoneal fluoxetine administration

Fluoxetine (FLX) and the N-desmethyl metabolite, norfluoxetine (NFLX) in rat brain microdialysis samples were determined by high-performance liquid chromatography (HPLC) with fluorescence detection using pre-column derivatization with 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F). In vitro experiment showed that the relative recovery of FLX across microdialysis membrane was enhanced by adding β-cyclodextrin (β-CD) or β-CD polymer to microdialysis perfusion fluid. The perfusion fluid containing β-CD polymer, which has polymeric glyceryl linkers attached to the hydroxyl group, gave the better recovery with satisfactory precisions. Using 1% β-CD polymer in Ringer’s solution as the perfusate, in vivo rat brain microdialysis experiment on intraperitoneal administration of FLX (10 mg/kg) to rats was carried out. The fluorescence peaks of FLX and NFLX appeared later than 30 min after the administration of FLX, and then, gradually increased with time. Two hours later, FLX reached a plateau level, but NFLX slowly increased, and at 24-48 h, NFLX levels were higher than FLX levels. These data suggest that long distributions of FLX and the potent metabolite, NFLX, in brain contributed to the long-term drug actions in vivo.     

Evaluation of thermoporometry for characterization of mesoporous materials

The accuracy of thermoporometry (TPM) in terms of the characterization of SBA-15 is examined based on a model that classifies the water in the mesopores into two different types: freezable pore water, which can form cylindrical ice crystals, and nonfreezable pore water, which cannot undergo a phase transition during a differential scanning calorimetry (DSC) measurement. Applying the empirical relationship between the sizes of the ice crystals formed in the mesopores and the solidification temperature of the freezable pore water to a thermogram (a recording of the heat flux during the solidification of the freezable pore water) yielded a size distribution of the ice crystals. The size of the ice crystals increased slightly with repetitive freezing, indicating that the mesopores were enlarged by formation of the ice crystals. Adding the thickness, t(nf), of the nonfreezable pore water layer to the ice crystal-size distribution calculated from the thermogram allowed for the determination of the porous properties of SBA-15. The porous properties attained from TPM experiments were compared with the results attained through the combination of Ar gas adsorption experiments and nonlocal density functional theory (NLDFT) analysis. The porous properties determined by TPM were confirmed to be quite sensitive to the t(nf) value.     

Oligoribonucleotide synthesis by the use of 1-(2-cyanoethoxy)ethyl (CEE) as a 2′-hydroxy protecting group

A novel method for the synthesis of oligoribonucleotides using 1-(2-cyanoethoxy)ethyl (CEE) as a 2′-hydroxy protecting group has been developed. A CEE group was introduced to the 2′-position of N-acyl-3′,5′-O-silyl-protected ribonucleosides under acidic conditions in good yields. The 2′-O-CEE group was found to be stable in an aqueous or ethanolic ammonia and was quickly removed by treatment with anhydrous tetrabutylammonium fluoride (TBAF). A combination of the use of N-acyl and 2′-O-CEE protecting groups enabled a reliable and complete two-step deprotection, first with NH₃–EtOH, then with TBAF in THF, without cleavage of internucleotidic linkages.     

An extension of the Harano-Ooshima rate expression for enzymatic hydrolysis of cellulose to account for changes in the amount of adsorbed cellulase

Three empirical rate expressions, Kinetics I, II, and III, for the enzymatic hydrolysis of cellulose were evaluated in an effort to develop a easy-to-use rate expression. They are based on the following equation:-dV/dX = kV, where V and X are the hydrolysis rate and the fractional conversion. In Kinetic I,k is constant. In Kinetic II, a linear relatinship betweenk and t is assumed. In Kinetic III, an exponential relationship is assumed. The three expressions were applied to enzymatic hydrolysis carried out under seven different conditions in which the kinds of substrates, enzymes, and initial concentrations were varied. All of the examined rate expressions were applied to the hydrolysis with success, but the better accuracies were obtained by Kinetic III, Kinetic II, and Kinetic I in this order. The variations ofk with time found in this study, especially the exponential relationship, were consistent with the effect of the measured changes in the concentration of adsorbed enzyme as predicted by theory developed previously by Ooshima et al. (1).     

脂环族环氧树脂和螺环原碳酸酯的光引发正离子共聚合

<正> 无收缩单体-1,6,8,13-四氧螺[7,7]十三碳烷(SOC_7)和3,4-环氧基环己烷甲酸3',4'-环氧基环己烷甲酯(ERL-4221)的光引发正离子共聚合的研究结果表明,少量SOC_7加到ERL-4221体系中可抑制固化收缩没有明显降低热性能。ERL-4221对SOC_7的合适克分子比为4比1,由此得到T_g为203℃而聚合时体积收缩为4.4％的交联共聚物。