Confirmation of the structures of kuwanons G and H (albanins F and G) by partial synthesis

Conclusive evidence is presented supporting structures $\text{1}$ and $\text{2}$ for two natural Diels-Alder adducts isolated from mulberry and designated as kuwanon G (albanin F, moracenin B) and Kuwanon H (albanin G, Moracenin A).     

Synthesis of cationic hydride and related complexes of palladium and nickel with tricyclohexylphosphine or triisopropylphosphine

The preparation and characterization of a series of cationic hydride complexes of palladium and nickel of the type [MH(L)(PCy₃)₂]BPh₄ (M = Pd, Ni; L = pyridines, pyrazole, imidazole; Cy = cyclohexyl; Ph = phenyl) from new hydride complexes, trans-MH(NO)₃(PCy₃)₂ are described. Trans-PdH(NO₃)(PCy₃)₂ is prepared conveniently by treatment of Pd(NO₃)₂(PCy₃)₂ (yellow form) with NaBH₄ (yield 93%). The relative stability of the nickel triad hydride complexes is discussed.Preparation of PdHCl(PR₃)₂ (R = Cy or i-Pr = isopropyl) by a new method and their derivatives are also reported.     

Laser-induced potential jump at the electrochemical interface probed by picosecond time-resolved surface-enhanced infrared absorption spectroscopy

Picosecond time-resolved surface-enhanced infrared absorption spectroscopy (SEIRAS) has been used for the first time to examine the potential jump at the electrochemical interface induced by a visible pulse irradiation. The potential dependent shift of the C-O stretching vibration of CO adsorbed on a Pt electrode was utilized to monitor the potential jump. A 6-cm(-1) red-shift was observed with a time delay of approximately 200 ps with respect to a visible pump-pulse irradiation (532 nm, 35 ps duration, 3 mJ cm(-2)). The observed red-shift is ascribed to the heating of the in-plane frustrated translational mode of CO and the negative shift of potential. These two contributions can be separated with the aid of the transient of the background reflectivity of the electrode surface. The heating of water layers near the surface is mainly responsible for the potential jump through the orientation change of water molecules. This method is promising as a tool to examine ultrafast electrode dynamics.     

High-speed solubility screening assay using ultra-performance liquid chromatography/mass spectrometry in drug discovery

Ultra-performance liquid chromatography (UPLC) was investigated as an alternative to high-performance liquid chromatography (HPLC) for analyzing pharmaceutical drug candidates. We previously developed a 96-well-based high-speed solubility assay system (HSSOL) using HPLC/UV and a LogD assay system (HSLogD) using HPLC/MS [Y. Dohta, T. Yamashita, S. Horiike, T. Nakamura, T. Fukami, Anal. Chem. 79 (2007) 8312]. We have introduced the UPLC/MS system into this previously developed HSSOL system to increase throughput. Results obtained by the UPLC/MS and HPLC/UV systems showed good agreement, validating the usefulness of the UPLC/MS system. A high-speed solubility assay system was developed employing the UPLC/MS system, thereby tripling the throughput.     

Investigation of intermolecular interaction in molecular complex of tryptamine and benzoic acid by solid-state 2D NMR

Solid-state NMR spectra and powder X-ray diffraction of the two-component molecular complex composed of tryptamine and benzoic acid were observed to investigate the intermolecular interaction in the molecular complex. 1D (13)C CP/MAS NMR spectrum and powder X-ray diffraction pattern of the complex was clearly different from the convolution of each spectrum of the single component. 2D (1)H-(13)C heteronuclear-correlation (HETCOR) NMR technique indicated that the intermolecular interaction between the primary amine of tryptamine and the carboxyl group of benzoic acid must be related to the complex formation.     

Enantiomorphism in the super helices of poly-γ-benzyl-glutamate

Summary Aggregates of poly--benzyl-d (orl-glutamate were precipitated by mixing of its solution in dimethylformamide or dioxane with propionic acid. Electron micrographs showed that the aggregates were composed of well-developed helical fibrils. The sence of helix was right-handed for thed-isomer and left-handed for thel-isomer; an enantiomorphic relation was shown for the helical aggregate of optical active macromolecule. Two recent publications have given conflicting results for the helical sense of the aggregate. This seems to be ascribed to carelessness in determining the helical sense from the electron micrographs.

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Zusammenfassung Es wurden Aggregate von Poly--benzyl-d (oderl)-glutamat durch Mischung von deren Lösung in Dimethylformamid oder Dioxan mit Propionsäure ausgefällt. Die elektronenmikroskopischen Bilder zeigen, daß die Aggregate aus gut ausgebildeten Helixfibrillen bestehen. Der Drehsinn der Helix war rechtsläufig für dasd-Isomer und linksläufig für dasl-Isomer. Eine enantiomorphe Beziehung läßt sich für die Helix-Aggregate zu den optisch aktiven Strukturen der Makromoleküle zeigen. Zwei kürzliche Veröffentlichungen ergaben zu dem hier Festgestellten widersprüchliche Ergebnisse über den Schraubensinn der Helices der aggregate. Dies scheint der Sorglosigkeit bei der Bestimmung des Schraubensinns von elektronenmikroskopischen Bildern zuzuschreiben zu sein.

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With 1 figure in 3 details     

Intermolecular forces for hydrogen,nitrogen and acetylene

Orientation-dependent intermolecular potentials for H₂, N₂, and C₂H₂ have been determined on the basis of electron charge density contours, octopolar induction in the dispersion force, electrostatic quadrupolar interaction, and the observed second virial coefficients. The recently settled structure of low-temperature solid acetylene has been discussed.     

Syntheses and structures of Tetranuclear Cluster complexes of molybdenum [Mo4(μ3-S)2(μ2-S)4 X 2-(PMe3)6] (X = SH,Cl, Br,I, SCN) and [Mo4(μ3-S)2-(μ2-S)4 (dtc)2(PMe3)4] (dtc = diethyldithiocarbamate)

A molybdenum cluster complex [Mo₄(μ₃-S)₂(μ₂-S)₄)(SH)₂(PMe_{3 6}] has been synthesized by the reaction of (NH₄)₂Mo₃S₁₃ with trimethylphosphine. The cluster core is composed of four molybdenum atoms arranged in the rhombus bridged by two capping and four bridging sulfur atoms. Two SH and six tri-methylphosphine ligands are coordinated to the terminal positions. The mean oxidation stares of molybdenum is +3.5 and there are five Mo-Mo bonds consistent with ten metal cluster electrons. The complex has been converted into [Mo₄(μ₃-S)₂(μ₂-S)₄ X ₂(PMe₃)₆] (X=Cl, Br, I, SCN) and [Mo₄μ₃-S₂(μ₂-S)₄ (die)₂(PMe₃)₄] (dtc - diethyldithiocarbamate). In the case of the dtc complex, two terminal trimetlaylphosphine ligands are displaced and dtc ligands are coordinated in chelate fashion. The structures of the SH, Cl, Br, and dtc complexes have been determined by X-ray crystallography. Molecular orbital calculations with DV-Xα method has shown large HOMO-LUMO gaps (1.52-1.74eV) for [Mo₄S₆ X ₂(PH₃)₄] (X= SH, Cl, and Br).     

Linear Multiselenium Interactions in Dicationic Oligomers of 1,5-(Diselena)canes: Behavior of Semc σ(mcc-nee) (6≤mc≤16) Elucidated with QTAIM Dual Functional Analysis

The intrinsic dynamic and static nature m_c center-n_e electron interactions of the σ-type σ(m_cc-n_ee) were elucidated for the Se-Se interactions in dicationic oligomers of Se(CH₂CH₂CH₂)₂Se ( 1 (Se, Se)) [ n ²⁺ (Se, Se): n=1–8], especially for m_c≥6, where n ²⁺ (Se, Se: n=1–8) are abbreviated by n ²⁺ (n=1–8), respectively. QTAIM dual functional analysis (QTAIM-DFA) was applied to the interactions. Perturbed structures generated using coordinates derived from the compliance constants (C_ii) were employed for QTAIM-DFA. Each Se-*-Se in 1 ²⁺ and 2 ²⁺ has the nature of CT-TBP (trigonal bipyramidal adduct formation through CT) and Cov-w (weak covalent), respectively, which supply the starting points of the investigations. The asterisk emphasizes the existence of a bond critical point on the interaction. All Se-*-Se in 3 ²⁺ are classified by the regular closed shell (r-CS) interactions and characterized as CT-MC (molecular complex formation through CT), which are denoted as r-CS/CT-MC, except for the central interaction, of which nature is r-CS/CT-TBP. Most interactions in 4 ²⁺– 8 ²⁺ are r-CS/t-HB_wc (typical-HB with covalency) but some are pure-CS/t-HB_nc (t-HB with no covalency). The linear Se_2n²⁺ interactions in 2 ²⁺– 8 ²⁺ seem close to those without any limitations, since the nature of Se-*-Se inside and outside of (CH₂CH₂CH₂)₂ are very similar with each other. The linear Se_2n²⁺ interactions in 3 ²⁺– 8 ²⁺ are shown to be analyzed as σ(m_cc-n_ee: 6≤m_c≤16), not by the accumulated σ(3c–4e).     

Liquid crystal formation of RecA-DNA filamentous complexes

Spontaneous optical birefringence of RecA-bound linear and closed circular single-stranded DNA filaments, as well as RecA self-assembled polymer, was observed in aqueous buffer solutions, which demonstrates the formation of lyotropic liquid crystalline phases.