Cowaniin, a C-glucosidic ellagitannin dimer linked through catechin from Cowania mexicana

A new complex tannin, cowaniin (1) was isolated from the leaves and stems of Cowania mexicana (Rosaceae), and its structure was characterized as novel C-glucosidic tannin dimer linked through (+)-catechin on the basis of spectral and chemical evidence. The inhibitory effect on activation of the Epstein-Barr virus early antigen was assessed for cowaniin. Six known polyphenols and related compounds, including a nitrile glucoside, purshianin, were also characterized.     

Synthesis and evaluation of 2-Nonylaminopyridine derivatives as PPAR ligands

To find novel PPAR ligands, we prepared several 3-{3 or 4-[2-(nonylpyridin-2-ylamino)ethoxy]phenyl}propanoic acid derivatives which were designed based on the structure of our previous PPARgamma ligand 1. In PPAR binding affinity assays, compound 4, which had an ethoxy group at the C-2 position of the propanoic acid of 1, showed selective binding affinity for PPARgamma. Compound 3, with an ethyl group at the C-2 position, was found to be a PPARalpha/gamma dual ligand. Compound 6, the meta isomer of 1, has been shown to be a PPARalpha ligand. The introduction of methyl (7) and ethyl (8) groups to the C-2 position of the propanoic acid of 6 further improved PPARalpha-binding potency. In cell-based transactivation assay, compounds 3 and 4 showed dual-agonist activity toward PPARalpha and PPARgamma. Compound 6 was found to be a triple agonist and compound 8 proved to be a selective PPARalpha agonist. In the human hypodermic preadipocyte differentiation test, it was demonstrated that the maximal activity of compounds 3 and 4 was higher than that of rosiglitazone.     

Tensyuic acids, new antibiotics produced by Aspergillus niger FKI-2342

Six new alkylitaconic acids, designated tensyuic acids A to F, were isolated from the culture broth of Aspergillus niger FKI-2342 by solvent extraction, silica gel column chromatography and HPLC. Their structures were elucidated by spectroscopic analysis including UV, NMR, and MS. They are all alkylitaconic acid derivatives. Only tesyuic acid C showed moderate antimicrobial activity against Bacillus subtilis.     

Which is reactive in alkaline solution, boronate ion or boronic acid? Kinetic evidence for reactive trigonal boronic acid in an alkaline solution

That boronic acid is a reactive species toward a diol moiety even in an alkaline solution and that the boronate ion is not very reactive were demonstrated by the estimated upper limit of the rate constants for the reactions of some boronic acids with 2,2'-biphenol and 2,3-dihydroxynaphthalene in a neutral-alkaline solution, which will correct a common misunderstanding in boron chemistry and would renew the idea of effective boronic acid sensor design for carbohydrates.     

Pressure-induced reentrant micellization of amphiphilic block copolymers in dilute aqueous solutions

The pressure-induced structural changes of a block copolymer, poly(2-ethoxyethoxyethyl vinyl ether)-block-poly(2-hydroxyethyl vinyl ether) (pEOEOVE-b-pHOVE) in aqueous solutions, were studied by means of small-angle neutron scattering (SANS) and dynamic light scattering (DLS) from atmospheric pressure up to 400 MPa. pEOEOVE-b-pHOVE formed a spherical micellar structure above 40 degrees C due to poor solubility of pEOEOVE. Micellization phase diagram was determined by DLS, and a covex-upward pressure-temperature (P-T) phase diagram was obtained having a peak around (P,T)=(150 MPa,48 degrees C). The SANS curves at 50 degrees C were analyzed as a function of P. The micellar core size decreased by pressurizing at low P's (P相似文献   

n-Propylpyridinium chloride-modified poly(dimethylsiloxane) elastomeric networks: preparation, characterization, and study of metal chloride adsorption from ethanol solutions

An n-propylpyridinium chloride-modified PDMS elastomeric network, PDMS/Py(+)Cl(-), was prepared from linear PDMS chains containing Si(CH(3))(2)OH end-groups cross-linked by 3-chloropropyltrimethoxysilane and posterior reaction with pyridine. PDMS/Py(+)Cl(-) material was structurally characterized by infrared spectroscopy (IR) and solid state (13)C and (29)Si NMR. Thermogravimetric analysis of the product showed good thermal stability, with the initial temperature of weight loss at 450 K. The ion-exchange capacity of the PDMS/Py(+)Cl(-) was 0.65 mmol g(-1). Metal halides, MCl(z) [M=Fe(3+), Cu(2+), and Co(2+)], were adsorbed by the modified solid from ethanol solutions as neutral species by forming the surface anionic complexes MCl(z+n)(n-). The nature of the anionic complex structure was proposed by UV-vis diffuse reflectance spectra. The species adsorbed were FeCl(-)(4), CuCl(2-)(4), and CoCl(2-)(4). The specific sorption capacities and the heterogeneous stability constants of the immobilized metal complexes were determined with the aid of computational procedures. The trend in affinities of PDMS/Py(+)Cl(-) for the metal halides were found to be FeCl(3)>CuCl(2) approximately CoCl(2).     

Total synthesis of borrelidin

The total synthesis of borrelidin has been achieved. The best feature of our synthetic route is macrocyclization at C11-C12 for the construction of an 18-membered ring after esterification between two segments. A detailed examination of the macrocyclization led us to the samarium(II) iodide-mediated intramolecular Reformatsky-type reaction as the most efficient synthetic approach. The two key segments were synthesized through regioselective methylation, directed hydrogenation, stereoselective Reformatsky-type reaction, and MgBr2.Et2O-mediated chelation-controlled allylation.     

Tryptophan 171 in Pharaonis phoborhodopsin (sensory rhodopsin II) interacts with the chromophore retinal and its substitution with alanine or threonine slowed down the decay of M- and O-intermediate

Pharaonis phoborhodopsin (ppR), also called pharaonis sensory rhodopsin II, NpSRII, is a photoreceptor for the photophobic response of Natronomonas pharaonis. Tryptophan 182 (W182) of bacteriorhodopsin (bR) is near the chromophore retinal and has been suggested to interact with retinal during the photoreaction and also to be involved in the hydrogen-bonding network around the retinal. W182 of bR is conserved in ppR as tryptophan 171 (W171). To elucidate whether W171 of ppR interacts with retinal during the photoreaction and/or is involved in the hydrogen-bonding network as in bR, we formed W171-substituted mutants of ppR, W171A and W171T. Our low-temperature spectroscopic study has revealed that the substitution of W171 to Ala or Thr resulted in the stabilization of M- and O-intermediates. The stability of M and absorption spectral changes during the M-decay were different depending on the substituted residue. These findings suggest that W171 in ppR interacts with retinal and the degree of the interaction depends on the substituted residues, which might be rate determining in the M-decay. In addition, the involvement of W171 in the hydrogen-bonding network is suggested by the O-decay. We also found that glycerol slowed the decay of M and not of O.     

Two-directional elaboration of hydroxyacetone under thermodynamically controlled conditions: allylation or 2-propynylation and aldol reaction

Enolate generated from O-(tetrahydropyran-2-yl)hydroxyacetone under thermodynamically controlled conditions (1.3 equiv of NaH, THF, 0 degrees C to rt) was allylated at the carbon bearing the protected hydroxy group with very high regioselectively. When tert-BuOH, equivalent to the excessive portion of initially added NaH, was introduced into the mixture followed by addition of aldehyde, aldol reaction took place on the methyl group to give 1-substituted 4-hydroxy-(1E),6-heptadien-3-one in acceptable yields after acidic treatment of the mixture for dehydration and deprotection. Introducing a chiral auxiliary protecting group into hydroxyacetone led to asymmetric allylation though stereoselectivity was around 50% ee. Thus, the hidden aspect of the chemoselective nature of protected hydroxyacetone-derived enolate generated under thermodynamically controlled conditions has opened a new avenue for two-directional elaboration of hydroxyacetone that should be potentially useful in organic synthesis.     

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.