Constituents of leaves of Phellodendron japonicum MAXIM. and their antioxidant activity

Three new flavonoid derivatives, 6'-O-acetyl amurensin (1), 6'-O-acetyl phellamurin (3) and (2R)-phellodensin-F (5), together with thirty known compounds have been isolated from the leaves of Phellodendron japonicum MAXIM. Their structures were established by means of spectroscopic analysis, including extensive 2D NMR and Mass spectra. The known compounds were identified by comparison with published physical and spectral data. The isolated compounds were screened for their in vitro antioxidant activity through DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging assay. Compounds quercetin and phellodenin-A demonstrated significant radical scavenging activity.     

Porous Protein Crystals as Catalytic Vessels for Organometallic Complexes

Porous protein crystals, which are protein assemblies in the solid state, have been engineered to form catalytic vessels by the incorporation of organometallic complexes. Ruthenium complexes in cross‐linked porous hen egg white lysozyme (HEWL) crystals catalyzed the enantioselective hydrogen‐transfer reduction of acetophenone derivatives. The crystals accelerated the catalytic reaction and gave different enantiomers based on the crystal form (tetragonal or orthorhombic). This method represents a new approach for the construction of bioinorganic catalysts from protein crystals.     

Structures of bulgecins,bacterial metabolites with bulge-inducing activity

The structure of bulgecin A, a bacterial metabolite with bulge-inducing activity, was determined chemically and spectrometrically to be 4-o-(2'-acetylamino-2'-deoxy-4'-o-hydroxysulfonyl-β-D-glucopyranosyl)-(2S, 4S, 5R -4-hydroxy-5-hydroxymethylprolyltaurine monosodium salt. Bulgecns B and C, the minor components, were found to be analogs of bulgecin A in which the taurine moiety was replaced as shown in Fig, 1.     

Chiral Catalysts Dually Functionalized with Amino Acid and Zn2+ Complex Components for Enantioselective Direct Aldol Reactions Inspired by Natural Aldolases: Design,Synthesis, Complexation Properties,Catalytic Activities,and Mechanistic Study

Aldolases are enzymes that catalyze stereospecific aldol reactions in a reversible manner. Naturally occurring aldolases include class I aldolases, which catalyze aldol reactions via enamine intermediates, and class II aldolases, in which Zn²⁺ enolates of substrates react with acceptor aldehydes. In this work, Zn²⁺ complexes of L ‐prolyl‐pendant[15]aneN₅ (ZnL³), L ‐prolyl‐pendant[12]aneN₄ (ZnL⁴), and L ‐valyl‐pendant[12]aneN₄ (ZnL⁵) were designed and synthesized for use as chiral catalysts for enantioselective aldol reactions. The complexation constants for L³ to L⁵ with Zn²⁺ [logK_s(ZnL)] were determined to be 14.1 (for ZnL³), 7.6 (for ZnL⁴), and 9.6 (for ZnL⁵), indicating that ZnL³ is more stable than ZnL⁴ and ZnL⁵. The deprotonation constants of Zn²⁺‐bound water [pK_a(ZnL) values] for ZnL³, ZnL⁴, and ZnL⁵ were calculated to be 9.2 (for ZnL³), 8.2 (for ZnL⁴), and 8.6 (for ZnL⁵), suggesting that the Zn²⁺ ions in ZnL³ is a less acidic Lewis acid than in ZnL⁴ and ZnL⁵. These values also indicated that the amino groups on the side chains weakly coordinate to Zn²⁺. We carried out aldol reactions between acetone and 2‐chlorobenzaldehyde and other aldehydes in the presence of catalytic amounts of the chiral Zn²⁺ complexes in acetone/H₂O at 25 and 37 °C. Whereas ZnL³ yielded the aldol product in 43 % yield and 1 % ee (R), ZnL⁴ and ZnL⁵ afforded good chemical yields and high enantioselectivities of up to 89 % ee (R). UV titrations of proline and ZnL⁴ with acetylacetone (acac) in DMSO/H₂O (1:2) indicate that ZnL⁴ facilitates the formation of the ZnL⁴ ? (acac)^? complex (K_app=2.1×10² M ^?1), whereas L ‐proline forms a Schiff base with acac with a very small equilibrium constant. These results suggest that the amino acid components and the Zn²⁺ ions in ZnL⁴ and ZnL⁵ function in a cooperative manner to generate the Zn²⁺‐enolate of acetone, thus permitting efficient enantioselective C? C bond formation with aldehydes.     

Micropatterning of copper on a poly(ethylene terephthalate) substrate modified with a self-assembled monolayer

We have developed a technique for the site-selective electroless deposition of Cu on poly(ethylene terephthalate) (PET) substrate modified with an organic self-assembled monolayer (SAM). The PET substrate was first modified with a silica-like layer by being dip-coated in an acetone solution of 3-aminopropyltrimethoxysilane and treated with UV light. The PET substrate was further modified with thiol groups using a 3-mercaptopropyltrimethoxysilane-SAM and then irradiated by UV light through a photomask to prepare thiol-group regions and OH-group regions. Cu was then deposited on only the thiol-group regions of the substrate by electroless deposition in a neutral solution with no catalysts by using dimethylamineborane as a reducing reagent. This site-selective deposition process can control the deposition conditions by an organic thin film fabricated on a surface-modified PET substrate, and thus can be applied to other low heat-resistant substrates.     

First-principles study of the pentacene/Cu(1 1 1) interface: Adsorption states and vacuum level shifts

We have studied the interaction of pentacene with a Cu(1 1 1) surface using density functional theory (DFT) within a generalized gradient approximation (GGA) and the van der Waals density functional [vdW-DF, M. Dion, H. Rydberg, E. Schröder, D.C. Langreth, B.I. Lundqvist, Phys. Rev. Lett. 92 (2004) 246401]. The adsorption energy is accurately predicted by vdW-DF, while the equilibrium distances between pentacene and the metal substrate (Z_C) are overestimated by both GGA and vdW-DF. The work function changes depend significantly on Z_C. The experimental work function change can be successfully reproduced by GGA if the experimentally reported adsorption geometry is used, whereas the magnitude of the work function change is underestimated if calculated adsorption geometries are applied. We examined the IDIS model [H. Vázquez, R. Qszwaldowski, P. Pou, J. Ortega, R. Pérez, F. Flores, A. Kahn, Europhys. Lett. 65 (2004) 802] to compare it with the GGA results. The interface dipoles estimated by the IDIS model fairly agree with the GGA results, provided that the adsorption distance is large. On the other hand, they tend to deviate from the GGA results as the adsorption distance becomes smaller, where back donation from the metal surface to the adsorbate occurs. Our analysis reveals that at experimentally reported metal–organic distance, back donation is significant enough to induce polarization of pentacene molecules perpendicular to the surface, which leads to a reduction of the work function. Thus, at the experimentally reported metal–organic distance, the work function change estimated by a simple IDIS model deviates from that calculated by self-consistent GGA calculations. We also found that at the experimentally reported metal–organic distance, the transferred electrons create weak chemical bonds between pentacene and the Cu(1 1 1) surface, illustrating the reactive nature of pentacene.     

Direct asymmetric anti-Mannich-type reactions catalyzed by a designed amino acid

The development of catalysts for Mannich-type reactions that afford anti-products with excellent diastereo- and enantioselectivities under mild conditions and low catalyst loadings (1-5 mol %) is reported. Based on principles gained from the study of (S)-proline-catalyzed Mannich-type reactions that afford enantiomerically enriched syn-products, (3R,5R)-5-methyl-3-pyrrolidinecarboxylic acid (RR35) has been designed to catalyze the direct enantioselective anti-selective Mannich-type reactions. Computational studies of the above reaction using HF/6-31G* level of theory suggested that this design would be highly effective. The catalyst was subsequently synthesized and studied in organocatalytic Mannich-type reactions between unmodified aldehydes and N-PMP-protected alpha-imino esters. In accord with the design principles and in quantitative agreement with the theoretical predictions, reactions catalyzed by this catalyst afforded anti-products in good yields with excellent diastereo- and enantioselectivities (anti:syn 94:6 to 98:2, >97 to >99% ee).