Samarium(II) iodide-induced tandem reductive coupling-Dieckmann condensation reaction: one-step synthesis of bicyclic oxacyclopentanecarboxylate from bis-α,β-unsaturated esters

The tandem cyclization of bis-α,β-unsaturated esters with SmI₂-Sm-THF in the presence of catalytic amount of methanol was found to stereoselectively provide bicyclo[4.3.0]nonan-8-ones and bicyclo[3.3.0]octan-3-ones.     

Synthesis and anti-tumor activity of new steroidal nuclear analogues of aragusterol A

3alpha,7alpha-Dihydroxy-5-epiaragusterol A (3) was synthesized from bile acid (cholic acid) as a new steroidal nuclear analogue of antitumor marine steroid aragusterol A. 7alpha-Hydroxyaragusterol A (4) was also derived from xestokerol B. The in vitro anti-proliferative activity of each of these analogues toward KB cells as well as in vivo anti-tumor activity of 5-epiaragusterol A (2) previously synthesized by the authors and 3 were assessed.     

Studies of CO adsorption on Pt(100), Pt(410), and Pt(110) surfaces using density functional theory

Adsorption of CO on Pt(100), Pt(410), and Pt(110) surfaces has been investigated by density functional theory (DFT) method (periodic DMol(3)) with full geometry optimization and without symmetry restriction. Adsorption energies, structures, and vibrational frequencies of CO on these surfaces are studied by considering multiple possible adsorption sites and comparing them with the experimental data. The same site preference as inferred experiments is obtained for all the surfaces. For Pt(100), CO adsorbs at the bridge site at low coverage, but the atop site becomes most favorable for the c(2 x 2) structure at 1/2 monolayer. For Pt(410) (stepped surface with (100) terrace and (110) step), CO adsorbs preferentially at the atop site on the step edge at 1/4 monolayer, but CO populates also at other atop and bridge sites on the (100) terrace at 1/2 monolayer. The multiple possible adsorption sites probably correspond to the multiple states in the temperature-programmed desorption spectra for CO desorption. For Pt(110), CO adsorbs preferentially at the atop site on the edge for both the reconstructed (1 x 2) and the un-reconstructed (1 x 1) surfaces. When adjacent sites along the edge row begin to be occupied, the CO molecules tilt alternately by ca. 20 degrees from the surface normal in opposite directions for both the (1 x 2) and (1 x 1) surfaces.     

A Convenient One-Pot Synthesis of Indane-1,2,3-triones by Oxidation of Indan-1-ones with N-Bromosuccinimide-dimethyl Sulfoxide Reagent

Indane-1,2,3-triones (2a-f) have been synthesized via bromination of indan-1-ones (1a-f), followed by oxidation of the resulting brominated indan-1-ones with dimethyl sulfoxide in one pot in good yields.     

Clarkson and Random Clarkson Inequalities for Lr(X)

We first show how (p,p′) Clarkson inequality for a Banach space X is inherited by Lebesgue-Bochner spaces L_r(X), which extends Clarkson's procedure deriving his inequalities for L_p from their scalar versions. Fairly many previous and new results on Clarkson's inequalities, and also those on Rademacher type and cotype at the same time (by a recent result of the authors), are obtained as immediate consequences. Secondly we show that if the (p, p') Clarkson inequality holds in X, then random Clarkson inequalities hold in L_r(X) for any 1 ≤ r ≤ ∞; the converse is true if r = p'. As corollaries the original Clarkson and random Clarkson inequalities for L_p are both directly derived from the parallelogram law for scalars.     

Surface EXAFS via differential electron yield

Surface‐sensitive analysis via extended X‐ray absorption fine‐structure (EXAFS) spectroscopy is demonstrated using a thickness‐defined SiO₂ (12.4 nm)/Si sample. The proposed method exploits the differential electron yield (DEY) method wherein Auger electrons escaping from a sample surface are detected by an electron analyzer. The DEY method removes local intensity changes in the EXAFS spectra caused by photoelectrons crossing the Auger peak during X‐ray energy sweeps, enabling EXAFS analysis through Fourier transformation of wide‐energy‐range spectral oscillations. The Si K‐edge DEY X‐ray absorption near‐edge structure (XANES) spectrum appears to comprise high amounts of SiO₂ and low Si content, suggesting an analysis depth, as expressed using the inelastic mean free path of electrons in general electron spectroscopy, of approximately 4.2 nm. The first nearest neighbor (Si—O) distance derived from the Fourier transform of the Si K‐edge DEY‐EXAFS oscillation is 1.63 Å. This value is within the reported values of bulk SiO₂, showing that DEY can be used to detect a surface layer of 12.4 nm thickness with an analysis depth of approximately 4.2 nm and enable `surface EXAFS' analysis using Fourier transformation.     

Lemnalol,a new sesquiterpenoid from the soft coral Lemnaliatenuis Verseveldt

The structure and absolute stereochemistry of lemnalol (1), a new ylangene-type sesquiterpenoid isolated from the soft coral $\text{Lemnalia}$$\text{tenuis}$ Verseveldt, has been established by spectroscopic, chemical, and x-ray crystallographic analyses.     

Total synthesis of marine prostanoids clavulones

An enantioselective and stereoselective synthesis of novel marine prostanoids clavulone II (1) and 12-O-desacetylclavulone II (2) has been accomplished.     

Microscopic Investigation of Ethylene Carbonate Interface: A Molecular Dynamics and Vibrational Spectroscopic Study

Ethylene carbonate(EC) liquid and its vapor-liquid interface were investigated using a combination of molecular dynamics(MD)simulation and vibrational IR, Raman and sum frequency generation(SFG)spectroscopies. The MD simulation was performed with a flexible and polarizable model of the EC molecule newly developed for the computation of vibrational spectra. The internal vibration of the model was described on the basis of the harmonic couplings of vibrational modes, including the anharmonicity and Fermi resonance coupling of C=O stretching. The polarizable model was represented by the charge response kernel(CRK),which is based on ab initio molecular orbital calculations and can be readily applied to other systems. The flexible and polarizable model can also accurately reproduce the structural and thermodynamic properties of EC liquid. Meanwhile, a comprehensive set of vibrational spectra of EC liquid, including the IR and Raman spectra of the bulk liquid as well as the SFG spectra of the liquid interface, were experimentally measured and reported. The set of experimental vibrational spectra provided valuable information for validating the model, and the MD simulation using the model comprehensively elucidates the observed vibrational IR, Raman, and SFG spectra of EC liquid. Further MD analysis of the interface region revealed that EC molecules tend to orientate themselves with the C=O bond parallel to the interface. The MD simulation explains the positive Im[χ~((2))](ssp) band of the C=O stretching region in the SFG spectrum in terms of the preferential orientation of EC molecules at the interface. This work also elucidates the distinct lineshapes of the C=O stretching band in the IR, Raman, and SFG spectra. The lineshapes of the C=O band are split by the Fermi resonance of the C=O fundamental and the overtone of skeletal stretching. The Fermi resonance of C=O stretching was fully analyzed using the empirical potential parameter shift analysis(EPSA) method. The apparently different lineshapes of the C=O stretching band in the IR, Raman, and SFG spectra were attributed to the frequency shift of the C=O fundamental in different solvation environments in the bulk liquid and at the interface. This work proposes a systematic procedure for investigating the interface structure and SFG spectra, including general modeling procedure based on ab initio calculations, validation of the model using available experimental data, and simultaneous analysis of molecular orientation and SFG spectra through MD trajectories. The proposed procedure provides microscopic information on the EC interface in this study, and can be further applied to investigate other interface systems, such as liquid-liquid and solid-liquid interfaces.