Novel,Complex Flavonoids from Mallotus philippensis (Kamala Tree)

One new flavanone, 4′‐hydroxyisorottlerin ( 2 ), and two new chalcone derivatives, kamalachalcones C ( 3 ) and D ( 4 ), were isolated from Mallotus philippensis (kamala tree). The largest compound ( 4 ; M_r 1098 g/mol) was shown to possess a unique, fused‐ring system made of two hydroxy‐chalcone units, giving rise to eight fused benzene/pyran units. From the same plant, the following six known compounds were also isolated: kamalachalcone A ( 5 ) and B ( 6 ), isoallorottlerin ( 7 ), isorottlerin ( 8 ), 5,7‐dihydroxy‐8‐methyl‐6‐prenylflavanone ( 9 ); 6,6‐dimethylpyrano(2″,3″: 7,6)‐5‐hydroxy‐8‐methylflavanone ( 10 ), and rottlerin ( 1 ). The structures of the new compounds were confirmed by in‐depth spectral analyses, including 2D‐NMR techniques, and the full ¹³C‐NMR assignments of the known flavanones 1 and 7 – 10 are published for the first time.     

Isolation and structures of trans-laurencenyne,a possible precursor of the C15 halogenated cyclic ethers,and trans-neolaurencenyne from laurencia okamurai

Isolation and structural elucidation of two new acetylenic polyenes, $\text{trans}$-laurencenyne $\text{1}$ and $\text{trans}$-neolaurencenyne $\text{2}$ from the marine red alga $\text{Laurencia okamurai}$ were carried out, the former compound $\text{1}$ very recently being proposed to be a biosynthetic precursor of the C₁₅ halogenated cyclic ethers, $\text{7}$ and $\text{8}$.     

Self-organization of supramolecular complex composed of rigid dendritic porphyrin and fullerene

A second-generation 1,3,5-phenylene-based dendritic porphyrin decorated with flexible alkyl chains exhibited a liquid crystallinity, and the inclusion of fullerene within the nanospace of the dendritic porphyrin strongly affected the mesophase structure in the thermotropic liquid-crystalline phase.     

Hybridization of layered niobates with cationic dyes

The hybridization of two different types of organic polycations, 1,1’-dimethyl-4,4’-bipyridinium dications (methyl viologen, MV²⁺) and 5,10,15,20-tetrakis(N-methyl-pyridinium-4-yl)-21H,23H-porphine tetracations (TMPyP⁴⁺), into layered niobates was investigated to construct an efficient dye-modified semiconductor for solar conversion and storage. Two different methods were employed for the direct intercalation of the cationic species, i.e., conventional ion-exchange with K₄Nb₆O₁₇ · 3H₂O as the starting host and a novel acid-base neutralization method with H₄Nb₆O₁₇ as the starting host. These two methods showed totally different behavior and the characteristic features of both will be discussed in relation to the structure of the hybrid formed, the amount of absorption observed for the guest molecules and the intercalation rates. An analysis of the photo-induced electron-transfer reactions will also be discussed to show how control of the intercalation of guest molecules affects the photofunctionality of these unique hybrids.     

Preparation of ultrathin films of aromatic polymides by vapor deposition polymerization from N-silylated aromatic diamines or aromatic tetracarboxylic dithioanhydride

A novel method for the preparation of ultrathin films of aromatic polyimides was developed through vapor deposition polymerization from combinations of monomer pairs of either N,N′-bis (trimethylsilyl)-substituted aromatic diamines and pyromellitic dianhydride or aromatic diamines and pyromellitic dithioanhydride. Both diamine component and tetracarboxylic dianhydride component were evaporated simultaneously at a stoichiometric molar ratio under vacuum, giving a deposited film on a substrate, which consisted of a polyamic acid derivative formed by the ring-opening polyaddition. The deposit was then converted to polyimide by thermal imidization at a relatively lower temperature, compared with a conventional method using the parent diamine and tetracarboxylic dianhydride. The properties of polyimide ultrathin films such as thermal stability, chemical resistance, and dielectric behavior were almost the same as those of the polyimide films prepared by a conventional method.     

Anodic modification of proline derivatives using a lithium perchlorate/nitromethane electrolyte solution

[reaction: see text] N-Acyliminium cation of prolines was efficiently generated to accumulate in an undivided cell at 0 degrees C by an anodic oxidation of N-acylprolines or alpha'-phenylsulfanylated N-acylproline derivatives in a lithium perchlorate/nitromethane solution. The iminium cation intermediates gave modified prolines by a reaction with nucleophiles under mild conditions.     

Solubilization of a water-insoluble dye in aqueous NaBr solutions of alkylpyridinium bromides and its relation to micellar size and shape

In order to investigate the effect of added salt on micelle size, shape, and structure the solubilization of Orange OT in aqueous NaBr solutions of decylpyridinium bromide (DePB), dodecylpyridinium bromide (DPB), tetradecylpyridinium bromide (TPB), and hexadecylpyridinium bromide (CPB) has been examined. The solubilization powers of DePB and DPB micelles increase with increasing NaBr concentration up to 2.86 and 3.07 mol dm^–3, respectively, but above these concentrations remain unaltered. This suggests that spherical micelles of DePB and DPB can have a maximum and constant size at NaBr concentrations higher than these threshold concentrations. On the other hand, the solubilization powers of TPB and CPB micelles increase in the whole range of NaBr concentration studied. The dependencies of the solubilization powers of their micelles on the counterion concentration change at 0.10 and 0.03 mol dm^–3 NaBr, respectively, as suggests that TPB and CPB micelles undergo the sphere–rod transition at those concentrations. Orange OT is a more suitable probe for detecting the presence of the maximum- and constant-size spherical micelle than Sudan Red B.     

A theoretical study on the substrate deacylation mechanism of class C beta-lactamase

The whole reaction of the deacylation of class C beta-lactamase was investigated by performing quantum chemical calculations under physiological conditions. In this study, the X-ray crystallographic structure of the inhibitor moxalactam-bound class C beta-lactamase (Patera et al. J. Am. Chem. Soc. 2000, 122, 10504-10512.) was utilized and moxalactam was changed into the substrate cefaclor. A model for quantum chemical calculations was constructed using an energy-minimized structure of the substrate-bound enzyme obtained by molecular mechanics calculation, in which the enzyme was soaked in thousands of TIP3P water molecules. It was found that the deacylation reaction consisted of two elementary processes. The first process was formation of a tetrahedral intermediate, which was initiated by the activation of catalytic water by Tyr150, and the second process was detachment of the hydroxylated substrate from the enzyme, which associated with proton transfer from the side chain of Lys67 to Ser64O(gamma). The first process is a rate-determining process, and the activation energy was estimated to be 30.47 kcal/mol from density functional theory calculations considering electron correlation (B3LYP/6-31G**). The side chain of Tyr150 was initially in a deprotonated state and was stably present in the active site of the acyl-enzyme complex, being held by Lys67 and Lys315 cooperatively.     

Enantioselective construction of quaternary carbon centers by catalytic [2 + 2 + 2] cycloaddition of 1,6-enynes and alkynes

[reaction: see text] The enantioselective [2 + 2 + 2] cycloaddition of 1,6-enynes and alkynes using chiral rhodium catalysts gave cycloadducts containing quaternary carbon stereocenters. Both symmetrical and unsymmetrical alkynes and acetylene could be used as coupling partners, and the corresponding bicyclic cyclohexa-1,3-dienes were obtained in good to excellent ee.     

Improved spectrophotometric determination of uranium(VI) with 4-(2-pyridylazo)resorcinol in the presence of benzyldimethylstearyltrimethylammonium chloride

An improved spectrophotometric determination of uranium(VI) is proposed using 4-(2-pyridylazo)resorcinol(PAR) in the presence of benzyldimethylstearyltrimethylammonium chloride(BSTAC) as a cationic surfactant. The calibration graph is linear in the range of 0.3–60 g/10 ml uranium(VI), measuring the absorbance at 550 nm. The reproducibility for 19.0 g/10 ml uranium(VI) is 0.57%. The third-derivative method using the third-derivative distance (d³A/d³) among ₁ 530 nm, ₃ 594 nm and ₂ 565 nm was also investigated.