Nanoscopic Imaging of meso‐Tetraalkylporphyrins Prepared in High Yields Enabled by Montmorrilonite K10 and 3 Å Molecular Sieves

We have developed a high‐yielding synthesis of meso‐tetraalkylporphyrins, which previously have been obtained only in lower yields. By employing Montmorrilonite K10 as the acid catalyst and 3 Å molecular sieves as the dehydrating agent, yields that reached 70 % could be achieved with some aliphatic aldehydes. The free‐base porphyrins with decyl ( C10 ) or longer chains were imaged at the single‐molecule level at the solvent/surface interface. Highly oriented pyrolytic graphite (HOPG) was used as a π‐stacking surface, whereas 1‐phenyloctane and 1‐phenylnonane were used as solvents. An odd–even effect was observed from C13 to C16 . For C13 a single‐crystal X‐ray structure allowed an unprecedented insight into how packing from two dimensions is expanded into a three‐dimensional crystal lattice.     

Secondary and auger electron spectra of a Cu-Be alloy

The slow secondary electron spectra corresponding to the copper rich surface and oxidized beryllium surface of Cu-Be alloys are observed after argon ion bombardment and heating treatment of the sample and they are identified by Auger electron spectroscopy.     

Angle-resolved investigation of Auger electrons from Cu and Au adsorbed on W(110)

The angular distribution of Cu M_2,3VV and Au N_6,7VV Auger electrons from Cu and Au mono- and double layers on W(110) is measured with the goal of obtaining information on the contribution of the backscattered wave on the angular distribution of Auger electrons from adsorbed atoms.     

Diastereomer-specific effects of double-stranded peptides conjugated with -L-Tyr-L-Phe- or -L-Tyr-D-Phe- residues on tyrosine phosphorylation and inhibition of src(ts)NRK, A431, MCF-7, and DU145 cell growth

The interaction between growth inhibition and chirality, especially of diastereomers, has an important modifying effect on cancer cell proliferation. Previously, we have reported on the design, synthesis, and chemical properties of a series of novel, double-stranded peptides, (y-AA-x-AA)(2)-(CH(2))(12), with -y-AA-x-AA- and -z-AA-y-AA-x-AA- sequences conjugated to the spacer. Here, we extend those results by showing that (D-, L-) and (L-, D-) diastereomers are more potent inhibitors of tyrosine phosphorylation than (L-, L-). Although the replacement of the L-Phe-L-Phe sequence with L-Tyr-L-Phe produces a less active inhibitor, the double-stranded peptide conjugated with L-Tyr-D-Phe is more active than that conjugated with L-Tyr-L-Phe. In addition, we show that SDS-PAGE gel profiles of tyrosine phosphorylation following treatment with bis(y-Tyr-x-Phe)-N,N-dodecane-1,12-diamine appear very similar to profiles of tyrosine phosphorylation following treatment with an analog of the tyrosine kinase inhibitor, erbstatin. Moreover, the level of autophosphorylation of the epidermal growth factor receptor kinase domain (EGFRKD) treated with bis(L-Tyr-D-Phe)-N,N-dodecane-1,12-diamine was lower than that seen following treatment with bis(L-Phe-D-Phe)-N,N-dodecane-1,12-diamine. These data provide new insights for the control of cancer cell proliferation through drug designs which replace the less active -L-Phe-L-Phe- (and -D-Phe-L-Phe-) with the more active -L-Tyr-L-Phe- (and -L-Tyr-D-Phe-) sequence.     

Chemo- and Enantioselective Oxidative α-Azidation of Carbonyl Compounds

We report high-performance I⁺/H₂O₂ catalysis for the oxidative or decarboxylative oxidative α-azidation of carbonyl compounds by using sodium azide under biphasic neutral phase-transfer conditions. To induce higher reactivity especially for the α-azidation of 1,3-dicarbonyl compounds, we designed a structurally compact isoindoline-derived quaternary ammonium iodide catalyst bearing electron-withdrawing groups. The nonproductive decomposition pathways of I⁺/H₂O₂ catalysis could be suppressed by the use of a catalytic amount of a radical-trapping agent. This oxidative coupling tolerates a variety of functional groups and could be readily applied to the late-stage α-azidation of structurally diverse complex molecules. Moreover, we achieved the enantioselective α-azidation of 1,3-dicarbonyl compounds as the first successful example of enantioselective intermolecular oxidative coupling with a chiral hypoiodite catalyst.     

Preparation of optically pure α-trifluoromethyl-α-amino acids from N-tosyl-2-trifluoromethyl-2-alkyloxycarbonyl aziridine

The preparation of optically pure α-trifluoromethyl-α-amino acids from N-tosyl-2-trifluoromethyl-2-alkyloxycarbonylaziridine is described. Optically pure aziridine was prepared with a 60% yield via three steps from optically pure 2,3-epoxy-1,1,1-trifluoropropane (TFPO). Ring-opening reactions of the aziridine with a variety of nucleophiles and subsequent deprotection of the N-tosyl moieties gave the optically pure β-substituted-α-trifluoromethyl-α-amino acids in moderate to good yields (up to 85%) without racemization at the quaternary stereogenic center of the amino acid.     

A Highly Efficient Macrolactonization Method via Ethoxyvinyl Ester

Facile and efficient macrolactonization of hydroxycarboxylic acid via ethoxyvinyl esters (EVEs), which can give 9‐ to 14‐membered macrolactones in good yields, has been developed (see scheme; DCE = 1,2‐dichloroethane). The method is useful for acid‐/base‐sensitive substrates and applicable to the compound with many functional groups.

     

Selective hydrogenation by polymer-encapsulated platinum nanoparticles prepared by an easy single-step sonochemical synthesis

Polypyrrole-encapsulated platinum nanoparticles (PPy/Pt-NPs) prepared by an easy single-step sonochemical synthesis were used as catalysts for the liquid phase hydrogenation of substituted alkenes in methanol or methanol/water mixtures. Polypyrrole (PPy) coatings on the nanoparticles were able to act as nanoscopic filters for substrates molecules, and consequently substrate selectivity could be controlled in the catalytic processes.     

Preparation of colored latex with polyurea shell by miniemulsion polymerization

Colored latexes with polyurea shell were prepared by applying interfacial polycondensation reaction to the miniemulsion polymerization process. These colored latexes were composed of polystyrene core and polyurea shell, and their particle size was adjusted to <100 nm. Diisocyanate was used as a hydrophobic monomer, and the equivalent mole of diamine was used as a hydrophilic monomer for interfacial polymerization. It was important to control the rate of interfacial polycondensation reaction in order to prepare small particles. Dye preservation property of colored latex loaded with oil-soluble dye was investigated. Polyurea shell formed at the surface of latex particles could restrain the migration of dyes from the latex particles and improve the dye preservation property. The ability to prevent dye migration depended on the composition of the polyurea shell.     

Improvement of the storage stability and photostability of colored latex prepared by miniemulsion polymerization

Polymer particles containing oil-soluble dyes (colored latex) were prepared by miniemulsion polymerization. The dye preservation properties of colored latex loaded with different types of dye were studied; preservation depended on the rate of dye diffusion and thus on the size of the dye molecules and the hardness of the polymer matrix in the latex particles. Hindered amine stabilizers (HAS) were used to improve the photostability of colored latex. The effect of HAS in colored latex was investigated both as an additive and as a comonomer. The photostability of latex particles containing a simple mixture of dye and HAS was improved with increasing HAS content up to 20% in particles. In the case of colored latex particles combined with HAS by a covalent bond, the optimal amount of HAS for photostability improvement was between 8 and 20%.