Synthesis of beta-analogues of C-mannosyltryptophan, a novel C-glycosylamino acid found in proteins

alpha-C-Mannosyltryptophan (alpha-C-Man-Trp) has been found to be a novel post-translational modification of tryptophan found from some biologically important glycoproteins. In order to analyze the biological functions of alpha-C-Man-Trp, we have developed an efficient synthetic strategy for alpha-C-Man-Trp and its glucose and galactose analogues, starting from alpha-C-glycosidation of the corresponding hexapyranoside derivatives with tinacetylene. According to the synthetic routes, we describe here syntheses of beta-anomers of C-Man-Trp, and its glucose and galactose analogues from the corresponding beta-C-glycosylacetylenes. During this study, we have developed a highly stereocontrolled synthesis of beta-C-mannosylacetylene that is required for the synthesis of beta-C-Man-Trp, while the precedented method gave an anomeric mixture of the C-mannosylacetylene. The synthetic C-Man-Trp and its analogues were analyzed by HPLC.     

A potential intermediate for the aza-Corey-Chaykovsky reaction: synthesis, structure, and thermolysis of a pentacoordinate 1,2-thiazetidine 1-oxide

Thermolysis of a pentacoordinate 1lambda(6),2-thiazetidine, which was synthesized for the first time and characterized by X-ray crystallographic analysis, gave the corresponding aziridine and a cyclic sulfinate almost quantitatively. The potential intermediacy of a 1lambda(6),2-thiazetidine was suggested in the aza-Corey-Chaykovsky reaction.     

pH-induced interconversion between J-aggregates and H-aggregates of 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin in polyelectrolyte multilayer films

We fabricated a layer-by-layer (LbL) film composed of 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TPPS) and poly(allylamine) (PAA) and investigated its pH response by UV-visible spectrometry. When the (PAA/TPPS)5PAA film was immersed in a pH 1.5 solution, J-aggregate bands were observed at 484 and 691 nm. Above pH 3.0, the J-aggregates were completely dissociated and an H-aggregate band was observed at 405 nm. The interconversion between the J-aggregates and H-aggregates in the LbL film was repeatable and controllable by changing the pH of the solutions.     

Triad distributions of 1,1-diphenylethylene–methyl acrylate copolymer determined from NMR study

The triad distributions of 1,1-diphenylethylene (D)–methyl acrylate (M) copolymers have been determined from NMR measurements and examined according to the terminal and penultimate models of copolymerization theory. As expected from the diamagnetic shielding by the phenyl rings of the nearest D units, the methoxy proton resonances were found to appear as three resolved peaks at 6.4–6.6 τ, 6.7–7.0 τ, and 7.2 τ, and have been assigned to the central M units of the triads MMM, MMD or DMM and DMD, respectively. The copolymer composition and the triad distributions observed are shown to agree better with the terminal model with the methyl acrylate reactivity ratio of 0.092 ± 0.010 than with the penultimate model.     

Effect of pretreatment on carbon oxidation activity over copper ion-exchanged zeolite catalysts

The carbon oxidation over copper ion-exchanged zeolites (Cu-MFI, Cu-MOR, Cu-FAU, and Cu-BEA) pretreated at 700 °C was investigated. The catalytic activities of Cu-MFI, Cu-MOR, and Cu-FAU pretreated at 700 °C were higher for carbon oxidation in NO + O₂ atmosphere than that of Cu-BEA. The TEM results demonstrated that Cu fine particles were formed on the external surface of Cu-MFI, Cu-MOR, and Cu-FAU, showing high activity. In addition, it was suggested that the coexisting NO plays an important role in enhancing the catalytic activity of Cu-MFI for carbon oxidation.     

Multilayered assemblies composed of brilliant yellow and poly(allylamine) for an optical pH sensor.

Multilayered thin films containing poly(allylamine) (PAA) and brilliant yellow (BY) were prepared on a quartz slide by a layer-by-layer (LBL) deposition technique. The UV-visible spectra of the PAA/BY films were sufficiently changed depending upon the pH value of the solution in which the film was immersed. The response of the PAA/BY films was very fast (within a second) upon pH change from 9.0 to 5.0, while the response time was ca. 100 s upon pH change from 5.0 to 9.0.