Taketoshi Kito

Immobilization of protein on monodispersed colloidal silica with poly(ethylene glycol) spacer and application of the composites to immunological agglutination tests

Abstract Surface modifications of monodispersed colloidal silica with poly(ethylene glycol) (PEG-COOH) silane coupling agents having a carboxyl end group, the successive immobilization of bovine serum albumin (BSA) and the application of the protein composites as an immunolatex were investigated. The reaction of the colloidal silica suspended in ethanol with the PEG-COOH coupling agents in the presence of small amounts of aqueous ammonia successfully gave PEG-COOH/SiO2 composites, retaining the particle size. Covalent binding of BSA to PEG/SiO2 composites was achieved by an activated ester method in the presence of an excess of the protein in pH 7.0 buffer. The agglutination tests using the BSA-PEG/SiO2 particles with anti-BSA antibody and γ-globulin derived from rabbits suggested applicability of the protein-PEG/SiO2 composites as immunoassay latexes.

Isopropylation of dibenzofuran over solid acid catalysts

Abstract The product compositions for the isopropylation of dibenzofuran over solid acid catalysts before and after reaching thermodynamic equilibrium (TE) were studied over H-silica-alumina and H-mordenite catalysts, and the shape selectivity of the latter was confirmed. For monoisopropylation over H-silica-alumina at 100–300°C for 2 h in an autoclave, the compositions of four isopropyldibenzofurans (MIPDBFs) before TE were in the following order: 2-MIPDBF=.4-MIPDBP > 62; 1-MIPDBF > 62; 3-MIPDBF. The compositions after TE were in the order: 4-MIPDBF > 62; 3-MIPDBF > 62; 2-MIPDBF > 62; 1-MIPDBF. Comparison between the two catalysts showed that the composition of 2-MIPDBF increased from 20–30% (over H-silica-alumina) to 48% (over H-mordenite). For diisopropylation under comparable conditions, the composition of 2,7-diisopropyldibenzofuran among its isomers also increased from 5–8 to 32%.

Stereochemistry of the products from the alkylation of 2-naphthol with glyoxal

Structural analyses of the products formed in the base-catalysed alkylation of 2-naphthol with glyoxal were performed by IR, 1H and 13C NMR spectroscopy and mass spectrometry. The final product, 7a,14c-dihydrobenzo[e]benzo[4,5]benzofuro[2,3-b]benzofuran (4), was determined to be in the cis rather than the trans form. MO calculations of the heats of formation and geometrical parameters also favour the cis form for 4. Two precursors of 4, 1,2-dihydronaphtho[2,1-b]furan-1,2-diol and 1-(2-hydroxy-1-naphthyl)naphtho[2,1-b]furan-2-ol, have also been analysed and their stereochemistry is discussed.

Preparation and Stereochemistry of the Isopropylidene Derivatives of 1,2‐Dihydronaphtho[2,1‐b]Furan‐1,2‐Diol and 1,2,9,10‐Tetrahydronaphtho[2,1‐b:7,8‐b′] Difuran‐1,2,9,10‐Tetraol in Comparison with the Corresponding Acetyl Derivatives

Abstract 1,2‐Dihydronaphtho[2,1‐b]furan‐1,2‐diol and 1,2,9,10‐tetrahydronaphtho[2,1‐b:7,8‐b′]difuran‐1,2,9,10‐tetraol were transformed into the corresponding isopropylidene derivatives, which were studied mainly by 1H NMR and chiral HPLC analyses in terms of a possible transformation mechanism and stereochemistry in comparison with their corresponding acetyl derivatives.

Base-catalysed Alkylation of 2,7-Naphthalenediol with Glyoxal. Isolation of Structurally Intriguing Products and their Stereochemistry

1,8-(2,5-Dihydroxy-1,4-dioxane-3,6-diyl)naphthalene-2,7-diol and 1,2,9,10-tetrahydronaphtho[2,1-b:7,8-b′]difuran-1,2,9,10-tetrol are prepared by reaction of 2,7-naphthalenediol with glyoxal, and their stereochemistry investigated mainly by NMR spectroscopy.

A kinetic study on asymmetric transfer hydrogenation of unsaturated acids and esters by alcohols with binuclear ruthenium(II) chiral diphosphine complexes

Kinetic investigation of the [Ru2Cl4{(–)-diop}3][diop = 2,2-dimethyl-4,5-bis(diphenylphosphinomethyl)-1,3-dioxolane] catalysed transfer hydrogenation of unsaturated acids and esters by alcohols indicated that the catalytically active [RuCl2{(–)-diop}] complex generated from the [Ru2Cl4{(–)-diop}3]⇌[RuCl2{(–)-diop}]+[RuCl2{(–)-diop}2] reaction afforded chiral hydrogenated products via the reaction of a hydrogen acceptor-[RuCl2{(–)-diop}](hydrogen donor) complex and of a hydrogen donor-[RuCl2{(–)-diop}](hydrogen acceptor) complex. 31P N.m.r. analysis of [Ru2Cl4{(–)-diop}3] in solution also suggested the possibility of [RuCl2{(–)-diop}3] formation from [Ru2Cl4{(–)-diop}3]. The reaction mechanism is also discussed on the basis of isotope effects observed in the [Ru2Cl4{(–)-diop}3] catalysed reaction between deuteriated benzyl alcohols and unsaturated species.