Synthetic study of yonarolide: stereoselective construction of the tricyclic core

Stereoselective construction of the tricyclic core of yonarolide (1), a marine norditerpenoid, was achieved. This synthetic route includes a Diels-Alder reaction and an intramolecular aldol condensation. It also involves efficient epimerization through a retro-Michael reaction-Michael addition and will be applicable to the total synthesis of 1.     

NO reduction by C3H6 over apatite-type A10(PO4)6(OH)2 (A?=?Ca and Sr)-supported Pt catalysts

A₁₀(PO₄)₆(OH)₂ (A = Ca and Sr)-supported Pt catalysts were prepared and their catalytic activity in NO reduction were investigated. The Sr₁₀(PO₄)₆(OH)₂-supported catalyst had high catalytic activity in the C₃H₆?CNO?CO₂ reaction; the activity was higher than that of the ??-Al₂O₃-supported catalyst at 300 °C. The basicity of the apatite supports would affect the chemical state of Pt on catalyst, resulting in promotion of NO reduction.     

Optimization of fluorescence property of the 8-oxodGclamp derivative for better selectivity for 8-oxo-2′-deoxyguanosine

2′-Deoxyguanosine (dG) suffers from oxidation by reactive oxygen species (ROS) to form 8-oxo-2′-deoxyguanosine (8-oxo-dG), which is regarded as a marker of oxidative stress in the cells. In our continuous study for the recognition molecule of 8-oxo-dG, 8-oxoGclamp and its derivatives have been identified as the selective fluorescent probe. However, it is an obstacle for further application that dG also forms a complex with 8-oxoGclamp, resulting in fluorescence quenching in less polar solvents. Quenching of the fluorescence of 8-oxoGclamp is thought to involve photo-induced electron transfer in the complex. It was hypothesized that the energy level of the excited state of 8-oxoGclamp and the HOMO energy of dG are the preliminary determinant of the quenching efficiency. Thus, fluorescence properties of the substituted derivatives at the 7-position of the 1,3-diazaphenoxazine part of 8-oxoGclamp were investigated. Among the new derivatives, fluorescence of the 7-phenyl substituted 8-oxoGclamp was not quenched by dG even in the stable complex, exhibiting the highest selectivity for 8-oxo-dG.     

Ruthenium-catalyzed conversion of sp3 C-O bonds in ethers to C-C bonds using triarylboroxines

Catalytic conversion of unreactive sp(3) C-O bonds in alkyl ethers to C-C bonds is described. Alkyl ethers bearing 2- or 4-pyridyl groups were coupled with triarylboroxines in the presence of a ruthenium catalyst. Triarylboroxines bearing a variety of functional groups including electron-withdrawing and -donating groups can be used for the reaction. No additional base was required for the coupling with the organoboron reagents, and base-sensitive groups can be tolerated. The reaction is considered to proceed via dehydroalkoxylation followed by addition of triarylboroxines to form C-C bonds.     

1,5]-H shift of aldehyde hydrogen in dienal compounds to produce ketenes

In 3-ethoxycarbonyl-2,4-dienal compounds, a thermal [1,5]-H shift of aldehyde hydrogen easily proceeded to produce the corresponding vinyl ketenes due to the remarkable substituent effect caused by the C3 ester group. The produced ketenes were captured by an alcohol and olefins to afford the corresponding esters and four-membered ring compounds, respectively.     

Efficient excited energy transfer reaction in clay/porphyrin complex toward an artificial light-harvesting system

The quantitative excited energy transfer reaction between cationic porphyrins on an anionic clay surface was successfully achieved. The efficiency reached up to ca. 100% owing to the "Size-Matching Rule" as described in the text. It was revealed that the important factors for the efficient energy transfer reaction are (i) suppression of the self-quenching between adjacent dyes, and (ii) suppression of the segregated adsorption structure of two kinds of dyes on the clay surface. By examining many different kinds of porphyrins, we found that tetrakis(1-methylpyridinium-3-yl) porphyrin (m-TMPyP) and tetrakis(1-methylpyridinium-4-yl) porphyrin (p-TMPyP) are the suitable porphyrins to accomplish a quantitative energy transfer reaction. These findings indicate that the clay/porphyrin complexes are promising and prospective candidates to be used for construction of an efficient artificial light-harvesting system.     

A hydrogenase model system based on the sequence of cytochrome c: photochemical hydrogen evolution in aqueous media

The diiron carbonyl cluster is held by a native CXXC motif, which includes Cys14 and Cys17, in the cytochrome c sequence. It is found that the diiron carbonyl complex works well as a catalyst for H(2) evolution. It has a TON of ～80 over 2 h at pH 4.7 in the presence of a Ru-photosensitizer and ascorbate as a sacrificial reagent in aqueous media.     

Optical characteristics of one-dimensional photonic crystals composed of high-aspect-ratio Si walls fabricated on V-grooved wafer

We demonstrate optical properties of one-dimensional photonic crystals (PC), which are fabricated using high-aspect-ratio etching on a V-grooved silicon wafer. The measured transmission spectrum has an obvious band gap; the suppression is over 30 dB. The quite small insertion loss of 1.9 dB is achieved by induced coupled plasma (ICP) cryogenic etching and direct coupling to the optical fiber aligned in the V-groove. We also successfully observed peaks originating from a localized cavity mode. Such a microcavity enables control of the light, which qualifies photonic crystal as a fundamental structure of optical functional devices. These results lead to achievement of integrated Si-based photonic circuits.     

Transcendence of the values of infinite products in several variables

The aim of this paper is to prove the transcendence of certain infinite products. As applications, we get necessary and sufficient conditions for transcendence of the value of $\Pi_{k=0}^{\infty}(1+a_{k}^{(1)}{z_{1}r^{k}}+\cdot\cdot\cdot+a_{k}^{(m)}{z_{m}r^{k}})$ at appropriate algebraic points, where r ≥ 2 is an integer and {a_n ⁽ⁱ⁾}_{n≥ 0} (1 ≤ i ≤ m) are suitable sequences of algebraic numbers.     

Infinitely many solutions for a nonlinear Schrödinger equation with general nonlinearity

We prove the existence of infinitely many solutions for

$$\begin{aligned} - \Delta u + V(x) u = f(u) \quad \text { in } \mathbb {R}^N, \quad u \in H^1(\mathbb {R}^N), \end{aligned}$$

where V(x) satisfies \(\lim _{|x| \rightarrow \infty } V(x) = V_\infty >0\) and some conditions. We require conditions on f(u) only around 0 and at \(\infty \).