Novel alkenylative cyclization using a ruthenium catalyst

Novel alkenylative cyclization of enyne was developed using Cp*RuCl(cod) under ethylene gas at room temperature.     

Precolumn derivatization of nucleotides based on fluorescent carbamate formation of the sugar moieties in high-performance liquid chromatography.

The fluorescence derivatization of nucleotides with 2-(5-chlorocarbonyl-2-oxazolyl)-5,6-methylenedioxybenzo++ furan in the presence of sodium azide and the separation of the derivatives by high-performance liquid chromatography are described. The reagent reacts with 5'-terminal hydroxyl groups of nucleotides to produce the corresponding fluorescent carbamates. The derivatives of mono- and oligonucleotides are separated by chromatography on a reversed phase column (TSKgel ODS-80TM) and the derivatives of octa- and deca-nucleotides on a size exclusion column (TSKgel G3000SWXL). The detection limits (signal-to-noise ratio = 3) are 0.8-6.0 pmol on column. 5'Phosphorylated nucleotide also gives a fluorescent derivative after alkaline phosphatase-mediated dephosphorylation.     

Adsorption of humic acid on goethite: isotherms, charge adjustments, and potential profiles

The adsorption of natural organic matter (NOM) on mineral (hydr)oxide plays an important role in the evaluation of the speciation of toxic metal ions in the environment. Because both NOM and mineral oxide have variable charges that adjust upon adsorption, a good understanding of proton binding is required before the binding of metal ions can be understood. In this study, the adsorption of purified Aldrich humic acid (PAHA) on goethite was examined as a function of the environmental conditions (pH, salt concentration, and free concentration of PAHA) together with the proton adsorption to PAHA, goethite, and their mixtures. The induced charges on both components were separated on the basis of the difference between the charge/pH curves of the mixture and those of the single components. The electrostatic potential profile across the adsorbed layer was obtained as a numerical solution of the Poisson-Boltzmann equation using the charge density of the adsorbed PAHA and the goethite surface. From the quantitative evaluation of the induced charge on both components, it is revealed that the degree of the charge adjustment is related to the electrostatic affinity between the PAHA segments and the goethite surface, the electrostatic repulsion between the PAHA segments, and the electrostatic shielding by salt ions. Considering the charge distribution of the adsorbed PAHA at the goethite surface, it is concluded that the change of the charge adjustment is sensitive to that of the conformation of the adsorbed PAHA. From the detailed inspection of the assumptions made and the comparison with the reported theoretical calculations, the obtained potential profiles are considered to broadly reflect the true potential profiles. Because a charge adjustment is not frequently considered in detail in relation to the NOM adsorption on metal (hydr)oxides, the obtained results can form the basis for the further development of modeling of the adsorption of NOM on (hydr)oxide surfaces.     

Preparation and thermosensitivity of naturally occurring polypeptide poly(gamma-glutamic acid) derivatives modified by propyl groups

Poly(gamma-glutamic acid) (gamma-PGA) is a biosynthetic polymer, and the carboxyl groups are able to undergo a chemical modification. In this study, poly(alpha-propyl gamma-glutamate) (gamma-PGA propylate) was synthesized by the esterification of these carboxyl groups to yield a thermosensitive and biodegradable polymer. In aqueous solution, the gamma-PGA propylate can impart thermosensitivity by controlling the hydrophobic-hydrophilic balance of the gamma-PGA polymeric chains.     

High-performance liquid chromatography of histamine and 1-methylhistamine with on-column fluorescence derivatization.

An on-column fluorometric derivatization method was developed for the determination of histamine and 1-methylhistamine (HMs) by high-performance liquid chromatography. The system for the derivatization consisted only of a commercially available single-plunger pump and a reversed-phase C18 column supported on synthetic polymer with a mobile phase of acetonitrile and alkaline borate buffer solution containing o-phthalaldehyde as a derivatization reagent. It required no additional reaction system as for a post-column derivatization method. Injected HMs might be derivatized to a fluorophore on the inlet site of the high-performance liquid chromatographic column, followed by chromatography on the same column. Optimization of the on-column reaction conditions resulted in a simple and sensitive analytical method for the determination of HMs with excellent reproducibility and linearity of 0.05-5 micrograms/ml of both HMs. Application of this method to the determination of HMs in food samples resulted in a limit of quantification of 0.05 mg/100 g and in a greater than 95% overall mean recovery at a fortification of 0.1 mg/g of both HMs. This method was furthermore applicable to the determination of histamine released from rat peritoneal mast cells.     

Thermal change of Alq3, tris(8-hydroxyquinolinato) aluminum(III) studied by TG and XRD-DSC

The thermal change of the tris(8-hydroxyquinolinato)aluminum (Alq₃) is currently investigated by XRD-DSC and TG. The phase transition of Alq₃ from α-phase to γ-phase takes place at 643–669 K. A very sharp peak with the peak temperature at approx. 709 K is ascribed to the melting of the Alq₃. The decomposition of the Alq₃ was observed accompanied with the melting and evaporation at >703K. The effect of the atmospheres on the mass loss procedure was studied by TG. It was found that thermal process of Alq₃ was strongly influenced by the partial pressure of water vapor in the atmosphere instead of oxygen.     

Selective generation of organic aggregates included within metal-organic micropores through vapor adsorption

The ethanol vapor adsorption behavior and the inclusion crystal structure of a 1D-transformable coordination polymer host were characterized. The adsorption jump was observed during phase transition or two-phase equilibrium with abnormal adsorption enthalpy caused by the nature of "mass induced phase transition." The included ethanol guests selectively form O-H...O hydrogen bonded pairs inside channels, suggesting selective construction of a specific cluster/aggregate in pores under control of thermodynamic factors and cooperative intermolecular interactions among the guest and channel surface.     

Large-scale separation of metallic and semiconducting single-walled carbon nanotubes

In the applications of single-walled carbon nanotubes (SWNTs), it is extremely important to separate semiconducting and metallic SWNTs. Although several methods have been reported for the separation, only low yields have been achieved at great expense. We show a separation method involving a dispersion-centrifugation process in a tetrahydrofuran solution of amine, which makes metallic SWNTs highly concentrated to 87% in a simple way.     

Simultaneous quantitative measurement of fourteen adrenal steroids by capillary column gas chromatography-mass spectrometry, and its clinical application

Until now, there has been little work covering all of the main native adrenal-cortical steroids in blood. We therefore established a method for the simultaneous quantitative measurement of 14 native adrenal-cortical steroids, which involves capillary column gas chromatography-mass spectrometry (GC--MS). Serum steroids were purified from serum with the Extrelut mini-column and then converted into stable derivatives for GC-MS by a combination of boronic cyclization and trimethylsilyl and methyloxime derivatization. The sensitivities (with a signal-to-noise ratio greater than or equal to 7) of our GC-MS method ranged from 0.1 to 1.0 ng/ml of serum, and the coefficients of variation of intra- and inter-assays were less than 19% for each steroid. Our newly devised method involving a capillary column GC-MS system has been proven to be a simple and suitable method for a diagnosis requiring simultaneous detection of many native adrenal steroids in clinical practice. The analysis time is only 4 h.     

Diastereoselective allylations of allyl-propargyl hybrid cations: synthesis of conjugated 1,5-dien-7-yne frameworks bearing C(4)-stereogenic centers

[reaction: see text] Chiral C(4)-substituted (E)- or (Z)-1-alkynyl-1-trimethylsilyloxy-2-butene systems provide anti-(Z) or syn-(Z) conjugated dienyne, with a very high level of stereocontrol, on treatment with BF(3).OEt(2) in CH(2)Cl(2) at -50 degrees C in the presence of allyltrimethylsilane. The Cieplak conformation for (E)-substrates and neighboring-group participation for (Z)-substrates are considered to be responsible for the stereochemical consequences.