Preparation and reaction of 2-aryl-3-silyl-1,3-butadiene

[reaction: see text] A conjugated pi-electron compound, 2-aryl-3-silyl-1,3-butadiene, was easily prepared from 1-benzyloxy-3-silyl-2-propyne, bis(iodozincio)methane, and an aryl halide in the presence of nickel catalyst. A subsequent cross-coupling reaction of the product with another aryl halide gave an unsymmetrical 2,3-diaryl-1,3-butadiene efficiently.     

Asymmetric cyclization of 2-alkenylphenols. A comparative study on the use of palladium(II) and titanium(IV) complexes

The oxidative cyclization of 2-(3-pentenyl)phenol catalyzed by [(η³-pinene)PdOAc]₂ gives optically active (+)-2-vinylchroman (25% e.e.), while (−)-2-(1-hydroxyethyl)chroman (56% e.e.) is formed as a single diastereomer upon treatment with t-BuOOH in the presence of Ti(OⁱPr)₄ and -(+)-diethyl tartrate. 2-(2-Butenyl)phenol also undergoes the Ti-promoted asymmetric cyclization to give (2S,1′R)-(−)-2-(1-hydroxyethyl)-2,3-dihydrobenzofuran (29% e.e.).     

Determination of sulfates of androsterone and epiandrosterone in human serum using isotope diluted liquid chromatography-electrospray ionization-mass spectrometry

A promising liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) for analysis of the sulfates of 5alpha-androgen, androsterone and epiandrosterone (A-S and EpiA-S) in human serum was developed. The method was used to assess one of the markers of 5alpha-reductase activity of males including patients with prostate cancer (PC). After deproteinization with acetonitrile, the androgen sulfates and the internal standard, [7,7,16,16-2H4]dehydroepiandrosterone-S, were extracted from human serum using a solid-phase extraction cartridge and washed with hexane. The extract was reconstituted and applied to the LC/ESI-MS system operated in the selected ion monitoring mode. The method was validated over the range 0.02-5 microg/mL (A-S) and 0.005-1.5 microg/mL (EpiA-S) using 10 microL of human serum. The method was a concise procedure without chemical or enzymatic hydrolysis of the conjugates, purification by high-performance liquid chromatography and/or derivatization, and proved to be satisfactory in its reproducibility and accuracy. The levels of these androgen sulfates tended to decrease during aging, and the A-S levels in the sera obtained from both healthy males and patients with PC were correlated with their EpiA-S levels.     

Improvement of latex piezoelectric immunoassay: Detection of rheumatoid factor

Latex piezoelectric immunoassay is a method for detection of agglutination of antibody- or antigen-bearing latex by immunoreaction using a piezoelectric quartz crystal; the agglutination decreases the oscillation frequency of the crystal. This is advantageous in that coating the surface of the crystal followed by fixation of antibody or antigen is unnecessary. There is, however, a drawback, and to improve this, we designed a micro-cell in which only one side of the crystal is exposed to the solution. A method for regenerating the crystal was also devised. Measurement was carried out using a calibration curve of the frequency change against rheumatoid factor activity. The improvement made it possible to use one crystal repeatedly and reproducibility was satisfactory. The calibration curve became almost independent of the crystal used.     

1,3-Rearrangement of ketene-N,O-acetals

Ketene N,O-acetals were prepared stereoselectively and submitted to a Lewis acid-mediated 1,3-rearrangement to afford C-alkylated products. The reactions proceeded in a stereoselective manner to construct a chiral quaternary carbon in high selectivity. The stereochemistry of the quaternary center was found to be opposite to that obtained by an anionic direct dienolate alkylation.     

Binding of methyl orange and the hydrophobic fluorescent probe, 2-p-toluidinylnaphthalene-6-sulfonate,by 2-dialkylaminoethyl methacrylate-N-vinyl-2-pyrrolidone and related copolymers

The copolymers of N-vinyl-2-pyrrolidone and 2-dimethylaminoethyl methacrylate, 2-diethylaminoethyl methacrylate, 2-dimethylaminoethyl acrylate, or 2-dimethylaminopropyl acrylamide have been prepared. Studies were made of the binding of a “binding probe,” methyl orange, by the copolymers in aqueous solution. The first binding constants accompanying the binding were evaluated. Furthermore, the intensity of fluorescence of a hydrophobic fluorescent probe, 2-p-toluidinylnaphthalene-6-sulfonate, in the presence of these polymers was investigated. The nature and phenomena of dye binding and hydrophobic fluorescent probe binding with the polymers are discussed.     

Structural Characteristics of Xyloglucan – Congo Red Aggregates as Observed by Small Angle X-ray Scattering

Xyloglucan is a type of hemicellulose with a cellulose backbone containing (1→6)-α-xylose or (1→2)-β-galactoxylose as a side chain. It is soluble in water. Its aqueous solution forms a gel or gel-like precipitate by addition of Congo red. Xyloglucan gel structures with various concentrations of Congo red were observed by small angle X-ray scattering (SAXS) at the nano-level. SAXS results indicated that the xyloglucan chains interacted with Congo red, and that an increase of concentration of Congo red induced a characteristic cross-linking domain, which consisted of a flat structure containing stacked xyloglucan chain assemblies. The Congo red molecules are inserted between the xyloglucan chains.     

Encapsulation of doxorubicin into liposomes by a freeze-thawing method using buffer solution

When doxorubicin was encapsulated into liposomes by freeze-thawing, the percentage of encapsulated doxorubicin (EN%) was found to vary according to the type of buffer solution used. The reason for this was investigated in the present report. Drug-free liposomes prepared by hydration were mixed with doxorubicin dissolved in a certain type of buffer solution that shows a pH decrease on freezing, and this mixture was subjected to freeze-thawing. Doxorubicin was encapsulated by the liposomes due to the difference in pH between freezing and thawing. EN% depended on the pH of the buffer solution before freezing and increased significantly at over pH 7. About 60% of doxorubicin was encapsulated into liposomes after the Ist freeze-thawing cycle, and EN% was increased gradually with the number of freeze-thawing cycles. The addition of sugar to the experimental system was seen to affect doxorubicin encapsulation and the particle size of liposomes.