Syntheses of linear ethoxysiloxanes by the oxidative condensation of triethoxysilane

Linear ethoxysiloxanes were synthesized by the oxidative condensation of hydrosilane. Triethoxysilane was subjected to oxidation to form triethoxysilanol, and pentaethoxydisiloxane was formed by the condensation reaction of triethoxysilane with triethoxysilanol. Pentaethoxydisiloxane was also subjected to oxidative condensation to form a mixture of nona- and decaethoxytetrasiloxanes. In contrast, pentaethoxydisiloxane, heptaethoxytrisiloxane, and nonaethoxytetrasiloxanes were subjected to the reaction with ethanol in the presence of zinc to isolate hexaethoxydisiloxane, octaethoxytrisiloxane, and decaethoxytetrasiloxane, respectively.     

Chalcogenation reactions of a stable ferrocenyldiphosphene: Formation of thia‐, selena‐, and telluradiphosphiranes

The reactions of TbtPPTbt (Tbt = 2,4,6‐tris[bis(trimethylsilyl)methyl]phenyl) with elemental sulfur and selenium in the presence of triethylamine resulted in the formation of the corresponding thia‐ and selenadiphosphiranes in 71% and 65%, respectively, whereas the tellurization reaction was unsuccessful probably due to the steric reason. On the other hand, treatment of TbtPPFc (Fc = ferrocenyl) with elemental sulfur, selenium, and tributylphosphine telluride afforded the corresponding thia‐, selena‐, and telluradiphosphiranes in 84%, 88%, and 66% yields, respectively. The molecular structures of these three‐membered heterocyclic compounds were confirmed by spectroscopic analysis. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:443–449, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20449     

Presence of β-Turn Structure in Recombinant Spider Silk Dissolved in Formic Acid Revealed with NMR

Spider dragline silk is a biopolymer with excellent mechanical properties. The development of recombinant spider silk protein (RSP)-based materials with these properties is desirable. Formic acid (FA) is a spinning solvent for regenerated Bombyx mori silk fiber with excellent mechanical properties. To use FA as a spinning solvent for RSP with the sequence of major ampullate spider silk protein from Araneus diadematus, we determined the conformation of RSP in FA using solution NMR to determine the role of FA as a spinning solvent. We assigned ¹H, ¹³C, and ¹⁵N chemical shifts to 32-residue repetitive sequences, including polyAla and Gly-rich regions of RSP. Chemical shift evaluation revealed that RSP is in mainly random coil conformation with partially type II β-turn structure in the Gly-Pro-Gly-X motifs of the Gly-rich region in FA, which was confirmed by the ¹⁵N NOE data. In addition, formylation at the Ser OH groups occurred in FA. Furthermore, we evaluated the conformation of the as-cast film of RSP dissolved in FA using solid-state NMR and found that β-sheet structure was predominantly formed.     

Selective extraction and purification of endohedral metallofullerene from carbon soot

A preferential extraction of endohedral metallofullerenes (EMFs) from carbon soot through the use of reduction in the extraction process and a convenient isolation of endohedral metallofullerene anions (EMFs(-)) and empty fullerenes utilizing their difference in solubility are accomplished. EMFs are easily isolated by one-stage high-performance liquid chromatography after chemical oxidation of the extracted endohedral EMFs(-).     

Fibrous and helical calcite crystals induced by synthetic polypeptides containing o-phospho-L-serine and o-phospho-L-threonine

The modification of CaCO(3) crystal growth by synthetic L-Ser(PO(3)H(2)) and L-Thr(PO(3)H(2)) containing polypeptides is described. The amino acids Gly, L-Glu, L-Asp, L-Ser, L-Ala, and L-Lys induced rhombohedral calcite with a rough surface. Dipeptides, Xaa-L-Ser(PO(3)H(2)) (Xaa = Gly, L-Glu, L-Asp, L-Ser, L-Ala and L-Lys) induced vaterite crystals in the lower [Ca(2+)]. On the other hand, L-Ser(PO(3)H(2))-containing polypeptides formed spherical vaterite and fibrous calcite. The characteristic helical calcite was found in the presence of copoly[L-Ser(PO(3)H(2))(75)L-Asp(25)] or poly[L-Ser(PO(3)H(2))(3)-L-Asp]. Fibrous calcite, spherical vaterite, and helical calcite crystals were subjected to XRD and EDX analysis. XRD revealed the specific faces of these crystals. EDX spectra and surface analysis visualized the localization of the polypeptides and CaCO(3) components. Together with TEM and SAED data, we propose hypothetical growth mechanisms for the fibrous and helical calcite crystals.     

Syntheses, characterization, and dioxygen reactivities of Cu(I) complexes with cis,cis-1,3,5-triaminocyclohexane derivatives: a Cu(III)2O2 intermediate exhibiting higher C-H activation

Six Cu(I) complexes with cis,cis-1,3,5-triaminocyclohexane derivatives (R3CY, R = Et, iBu, and Bn), [Cu(MeCN)(Et3CY)]SbF6 (1), [Cu(MeCN)(iBu3CY)]SbF6 (2), [Cu(MeCN)(Bn3CY)]SbF6 (3), [Cu(CO)(Et3CY)]SbF6 (4), [Cu(CO)(iBu3CY)]SbF6 (5), and [Cu(CO)(Bn3CY)]SbF6 (6), were prepared to probe the ability of copper complexes to effectively catalyze oxygenation reactions. The complexes were characterized by elemental analysis, electrochemical and X-ray structure analyses, electronic absorption spectroscopy, IR spectroscopy, 1H NMR spectroscopy, and ESI mass spectrometry. The crystal structures of 1-3 and 6 and the CO stretching vibrations (nuCO) of 4-6 demonstrate that the ability of R3CY to donate electron density to the Cu(I) atom is stronger than that of the previously reported ligands, 1,4,7-triazacyclononane (R3TACN) and 1,4,7-triazacyclodecane (R3TACD). Reactions of complexes 1-3 with dioxygen in THF or CH2Cl2 at -105 to -80 degrees C yield bis(mu-oxo)dicopper(III) complexes 7-9 as intermediates as confirmed by electronic absorption spectroscopy and resonance Raman spectroscopy. The Cu-O stretching vibrations, nu(Cu-O) for 7 (16O2: 553, 581 cm-1and 18O2: 547 cm-1) and 8 (16O2: 571 cm-1 and 18O2: 544 cm-1), are observed in a lower energy region than previously reported for bis(micro-oxo) complexes. The decomposition rates of complexes 7-9 in THF at -90 degrees C are 2.78 x 10-4 for 7, 8.04 x 10-4 for 8, and 3.80 x 10-4 s-1 for 9. The decomposition rates of 7 and 8 in CH2Cl2 were 5.62 x 10-4 and 1.62 x 10-3 s-1, respectively, and the thermal stabilities of 7-9 in CH2Cl2 are lower than the values measured for the complexes in THF. The decomposition reactions obeyed first-order kinetics, and the H/D isotope experiments for 8 and 9 indicate that the N-dealkylation reaction is the rate-determining step in the decomposition processes. On the other hand, the decomposition reaction of 7 in THF results in the oxidation of THF (acting as an exogenous substrate) to give 2-hydroxy tetrahydrofuran and gamma-butyrolactone as oxidation products. Detailed investigation of the N-dealkylation reaction for 8 by kinetic experiments using N-H/D at -90 degrees C showed a kinetic isotope effect of 1.25, indicating that a weak electrostatic interaction between the N-H hydrogen and mu-oxo oxygen contributes to the major effect on the rate-determining step of N-dealkylation. X-ray crystal structures of the bis(micro-hydroxo)dicopper(II) complexes, [Cu2(OH)2(Et3CY)2](CF3SO3)2 (10), [Cu2(OH)2(iBu3CY)2](CF3SO3)2 (11), and [Cu2(OH)2(Bn3CY)2](ClO4)2 (12), which have independently been prepared as the final products of bis(micro-oxo)dicopper(III) intermediates, suggest that an effective interaction between N-H and mu-oxo in the Cu(III)2(micro-O)2 core may enhance the oxidation ability of the metal-oxo species.     

Surface design for precise control of spatial growth of a mesostructured inorganic/organic film on a large-scale area

A microfabrication technique is presented to fabricate a mesostructured inorganic/organic composite film, i.e., silica/cetyltrimethylammonium chloride (CTAC) film, with near-perfect site-selectivity on a large surface area based on a spatially regulated growth method. To precisely regulate the site-selective growth of this mesocomposite film at the solid/liquid interface, we designed a novel microtemplate consisting of a "dual-component" self-assembled monolayer (SAM) with alternating hydrophobic trifluorocarbon (CF3) and cationic amino (NH2) groups. First, (heptadecafluoro-1,1,2,2-tetrahydrodecyl)trimethoxysilane (FAS)-SAM was formed onto Si substrate covered with native oxide (SiO2/Si) from vapor phase. The substrate was then photolithographically micropatterned using 172 nm vacuum UV light. Finally, the micropatterned FAS-SAM was immersed in a solution of 1 vol % (aminoethylaminomethyl)phenethyltrimethoxysilane (AEAMPS) in absolute toluene. Due to these treatments, a dual-SAM microtemplate with CF3- and NH2-terminated surfaces was fabricated, as evidenced by lateral force microscopy, ellipsometry, and X-ray photoelectron spectroscopy. Using this template, the microfabrication of a mesocomposite film was demonstrated. As a control, the micropatterned hydrophobic FAS-SAM template (composed of CF3- and OH-terminated surfaces) was also treated under the same conditions. Optical microscopy and atomic force microscopy confirmed that the formation of the continuous mesocomposite film proceeded only on the FAS-SAM-covered regions, while the AEAMPS-SAM-covered regions remained free of deposits. This shielding effect also remained constant regardless of the pattern's geometry, i.e., the interval distance between the FAS-SAM-covered areas in the pattern. Through this approach, we were able to obtain well-defined 5-, 10-, and 20-mum wide mesocomposite microlines over the entire 10 x 10 mm2 area with high area-selectivity. On the other hand, when the SiO2 regions were not terminated with the cationic NH2 groups, cluster formation proceeded not only on the hydrophobic CF3 regions but also on the SiO2 regions, particularly with an increase in the pattern interval distance, resulting in lower final pattern resolution.     

Adsorption of phosphate from seawater on calcined MgMn-layered double hydroxides

Adsorptive properties of MgMn-3-300 (MgMn-type layered double hydroxide with Mg/Mn mole ratio of 3, calcined at 300 degrees C) for phosphate were investigated in phosphate-enriched seawater with a concentration of 0.30 mg-P/dm3. It showed the highest phosphate uptake from the seawater among the inorganic adsorbents studied (hydrotalcite, calcined hydrotalcite, activated magnesia, hydrous aluminum oxide, manganese oxide (delta-MnO2)). The phosphate uptake by MgMn-3-300 reached 7.3 mg-P/g at an adsorbent/solution ratio of 0.05 g/2 dm3. The analyses of the uptakes of other constituents (Na+, K+, Ca(+, Cl-, and SO(2-)4) of seawater showed that the adsorbent had a markedly high selectivity for the adsorption of phosphate ions. Effects of initial phosphate concentration, temperature, pH, and salinity on phosphate uptake were investigated in detail by a batch method. The phosphate uptake increased slightly with an increase in the adsorption temperature. The adsorption isotherm followed Freundlich's equation with constants of logK(F)=1.25 and 1/n=0.65, indicating that it could effectively remove phosphate even from a solution of markedly low phosphate concentration as well as with large numbers of coexisting ions. The pH dependence showed a maximum phosphate uptake around pH 8.5. The pH dependence curve suggested that selective phosphate adsorption progresses mainly by the ion exchange of HPO(2-)4. The study on the effect of salinity suggested the presence of two kinds of adsorption sites in the adsorbent: one nonspecific site with weak interaction and one specific site with strong interaction. The effective desorption of phosphate could be achieved using a mixed solution of 5 M NaCl + 0.1 M NaOH (1 M = 1 mol/dm3), with negligible dissolution of adsorbent. The adsorbent had high chemical stability against the adsorption/desorption cycle; it kept a good phosphate uptake even after the repetition of the seventh cycle.     

Direct synthesis of hetero-biaryl compounds containing an unprotected NH2 group via Suzuki-Miyaura reaction

Hetero-biaryl compounds were prepared via the Suzuki-Miyaura coupling reaction of hetero-aryl moieties containing an unprotected NH₂ group and arylboronic acids. D-t-BPF was found to be an efficient ligand for the cross-coupling of NH₂-unprotected hetero-aryl chlorides with phenylboronic acid.     

Bitterness evaluation of medicines for pediatric use by a taste sensor

The purpose of this study was to evaluate the bitterness of 18 different antibiotic and antiviral drug formulations, widely used to treat infectious diseases in children and infants, in human gustatory sensation tests and using an artificial taste sensor. Seven of the formulations were found to have a bitterness intensity exceeding 1.0 in gustatory sensation tests (evaluated against quinine as a standard) and were therefore assumed to have an unpleasant taste to children. The bitterness intensity scores of the medicines were examined using suspensions in water or an acidic sports drink. In the case of three macrolide antibiotic formulations containing erythromycin (ERYTHROCIN dry syrup), clarithromycin (CLARITH dry syrup for pediatric), and azithromycin (ZITHROMAC fine granules for pediatric use), the bitterness intensities of suspensions in acidic sports drinks were dramatically enhanced compared with the corresponding scores of suspensions in water. This enhancement could be predicted using the taste sensor. On the other hand, a reduction of bitterness intensity was observed for an acidic sports drink suspension of an amantadine product (SYMMETREL fine granules) compared with an aqueous suspension. This reduction in bitterness could also be predicted using the taste sensor output value. Thus, the taste sensor could predict whether or not suspension in an acidic sports drink would enhance or reduce the bitterness intensity of pediatric drug formulations, compared with suspensions in water.