Structure Determination and Total Synthesis of (+)‐16‐Hydroxy‐16,22‐dihydroapparicine

Herein, we describe the first asymmetric total synthesis and determination of the relative and absolute stereochemistry of naturally occurring 16‐hydroxy‐16,22‐dihydroapparicine. The key steps include 1) a novel phosphinimine‐mediated cascade reaction to construct the unique 1‐azabicyclo[4.2.2]decane core, including a pseudo‐aminal‐type moiety; 2) a highly stereospecific 1,2‐addition of 2‐acylindole or a methylketone through a Felkin–Anh transition state for the construction of a tetrasubstituted carbon center; and 3) an intramolecular chirality‐transferring Michael reaction of the ketoester, with neighboring‐group participation, to introduce a chiral center at C15 in the target molecule. In addition, we evaluated the antimalarial activity of synthetic (+)‐(15S,16R)‐16‐hydroxy‐16,22‐dihydroapparicine and its intermediate against chloroquine‐resistant Plasmodium falciparum (K1 strain) parasites.     

Hydrogen/deuterium adsorption and absorption properties on and in palladium using a combined plane wave and localized basis set method

Detailed information on the H/D isotope effects for adsorption on the surface and absorption in the bulk is important for understanding the nuclear quantum effect. To achieve this, we developed a new theoretical approach, namely, the combined plane wave and localized basis set (CPLB) method. By using the multicomponent quantum chemical method, which takes into account the quantum effect of a proton or deuteron, with the localized part of the CPLB method, direct analysis of the H/D isotope effect about adsorption and absorption is carried out. In this study, we performed a theoretical investigation of the H/D isotope effects for adsorption on a Pd(111) surface and absorption in bulk Pd. We clearly showed an H/D isotope effect on geometry during adsorption and absorption. Our developed CPLB approach is a powerful tool for analyzing the quantum nature of H/D in surface, bulk, and inhomogeneous systems.     

Propagation of short-range order in the lattice gas

The lattice gas model is examined to make a comparison between the superposition approximation and one which is free from the approximation as long as the three-body distribution is concerned. The formulation is applied to the type I superionic conductor, AgI, in which Ag-ions can move like the atoms in liquid and give rise to a strongly correlated Ag-ion distribution over available lattice sites. The oscillatory behavior of the radial distribution function is found up to the seventh neighbor distances including three maxima and three minima. The degree of disordered arrangement is then examined by calculating the latent heat of transition from the ordered β-phase to disordered α-phase of the superionic conductor.     

Magnetic behavior and structural feature of quasi-one-dimensional BaCu2V2O8 crystal

Magnetic properties of BaCu₂V₂O₈ single crystals obtained by the spontaneous nucleation method using V₂O₅ as a self-flux are investigated. Singlet ground states with spin gaps of 215 and 223 K are observed along the directions parallel and perpendicular to the c-axis of the crystal, respectively, being in good agreement with powder sample measurements. Reinvestigation of the crystal structure reveals that the whole structural framework of BaCu₂V₂O₈ crystal can be described as an assembly of alternating chains, which are built by edge-sharing pairs of CuO₄ square-plaquettes and VO₄ tetrahedra along the c-axis. The magnetic nature of BaCu₂V₂O₈ is well understood based on this structural interpretation.     

Spongolactams, farnesyl transferase inhibitors from a marine sponge: isolation through an LC/MS-guided assay, structures, and semisyntheses

Novel nitrogenous diterpenoids, spongolactams A-C (1-3), were isolated as trace components of an Okinawan marine sponge, Spongia sp., by an LC/MS-guided assay for farnesyl transferase (FTase) inhibitors. Their structures were elucidated by spectroscopic analyses. To evaluate their structures and biological activity, the metabolites were semisynthesized from the known furanoditerpene 5, obtained from the same sponge. Three related compounds 4, 13, and 16 were also semisynthesized. The IC50 values against FTase for 1-3 were 23, 130, and >260 microM, respectively, while the IC50 values against a human tumor cell line were 2.0, 3.5, and 20 microM, respectively. The structure-activity relationships within the six compounds suggest some positive correlation between FTase inhibitory and cytotoxic activities.     

Studies toward the total synthesis of irumamycin: stereoselective preparation of the C(15)-C(27) segment via two-directional chain synthesis

The basic structure of the C(15)-C(27) part of irumamycin (1) was synthesized. Stereoselective assembly of C16, 17, 22, and an extra C21 stereocenter was achieved by two-directional Brown’s asymmetric allyl boration. Group selective PMP acetal formation and oxidative cleavage of vinyl group facilitated the differentiation of the ends of a two-directionally synthesized chain.     

Immobilization of photosystem I or II complexes on electrodes for preparation of photoenergy-conversion devices

Photosystems, PSI and PSII isolated from Thermosynechococcus elongatus were successfully immobilized on a TiO₂ nanostructured film for use in dye-sensitized biosolar cells (DSBCs). The photosystem complexes were also immobilized on an ITO electrode modified with 3-aminopropyltriethoxysilane by utilizing the interactions between the electrode and the surface of the PSI or PSII polypeptide. Illumination of the PSI and PSII complexes immobilized on the ITO electrode resulted in action spectra in the presence of methyl viologen, which corresponded to the absorption spectra of the complexes. Compared with the ITO electrode, PSI or PSII complexes assembled on the TiO₂ electrode had much higher energy-conversion efficiency in the presence of an iodide/triiodide redox system of an ionic-liquid-based electrolyte. This could have interesting applications in the development of DSBCs.     

Raman spectroscopy of liquid crystalline N-[4-(4-n-alkoxybenzoyloxy)-2-hydroxybenzylidene]-3-aminopyridines

New homologous series of N-[4-(4-n-alkoxybenzoyloxy)-2-hydroxybenzylidene]-3-aminopyridines were synthesized, they exhibited a nematic phase. The temperature dependence of their Raman spectra has been observed in the spectral range 900–1800?cm^?1. Some Raman bands show a marked change in their intensity and frequency through the phase transition from crystalline solid to nematic. These bands are ascribed to the vibrational modes related to the core part of the molecule. Such behaviour can be explained by the change of molecular conformation related to the core. Some members of these series exhibited photochromism in the solid state.     

Development of determination method of trace nickel in natural water by ID-oxygen added nitrogen-MIP-MS with direct measurement of liquid–liquid extracted organic phase

This work introduces the development of a novel determination method of trace nickel (ng l^–1 level) in natural water samples. Nickel in the water samples is liquid–liquid extracted into methyl isobutyl ketone (MIBK) as nickel-diethyldithiocarbamate (DDTC) complex, and isotope dilution-oxygen added nitrogen-microwave induced plasma mass spectrometry (ID-oxygen added nitrogen-MIP-MS) is conducted by direct measurement of the liquid–liquid extracted organic MIBK phase. The accuracy of the proposed method was confirmed by analysing certified reference materials (NRC NASS-5 seawater, NRC SLRS-3 riverine water and NRC SLRS-4 river water), and the analytical results obtained were in good agreement with the certified values. The detection limit for nickel is 1.3?ng?l^?1 when the water sample is 50 times concentrated. The precision as RSD is <4%. The proposed method was applied to clarify the concentration-depth vertical profiles of nickel in Lake Mashu, Japan, as the Baseline Station of the United Nations GEMS/Water (Global Environment Monitoring System/Water) Programme.