三溴异氰脲酸和DABCI-Br作为高效催化剂用于羟基硅烷化

The protection and deprotection of functionalgroups are indispensable in the synthesis of polyfunc-tional compounds.In addition,several chemical con-versions and multiple sequence syntheses are often re-quired for the protection of hydroxyl groups.Thesily…     

Structures, energetics, vibrational spectra of NH4+ (H2O)(n=4,6) clusters: Ab initio calculations and first principles molecular dynamics simulations

Important structural isomers of NH(4) (+)(H(2)O)(n=4,6) have been studied by using density functional theory, Moller-Plesset second order perturbation theory, and coupled-cluster theory with single, double, and perturbative triple excitations [CCSD(T)]. The zero-point energy (ZPE) correction to the complete basis set limit of the CCSD(T) binding energies and free energies is necessary to identify the low energy structures for NH(4) (+)(H(2)O)(n=4,6) because otherwise wrong structures could be assigned for the most probable structures. For NH(4) (+)(H(2)O)(6), the cage-type structure, which is more stable than the previously reported open structure before the ZPE correction, turns out to be less stable after the ZPE correction. In first principles Car-Parrinello molecular dynamics simulations around 100 K, the combined power spectrum of three lowest energy isomers of NH(4) (+)(H(2)O)(4) and two lowest energy isomers of NH(4) (+)(H(2)O)(6) explains each experimental IR spectrum.     

Total synthesis of (-)-saliniketals A and B

A stereocontrolled total synthesis of the orthinine decarboxylase inhibitors saliniketals A and B is described. Key features of the 17-step route include the use of two boron aldol/reduction sequences to control six of the nine stereocenters, an intramolecular Wacker-type cyclization to install the bicyclic acetal core, and a late-stage Stille coupling to append the requisite (2 Z,4 E)-dienamide.     

Cell culture arrays using magnetic force-based cell patterning for dynamic single cell analysis

In order to understand the behavior of individual cells, single cell analyses have attracted attention since most cell-based assays provide data with values averaged across a large number of cells. Techniques for the manipulation and analysis of single cells are crucial for understanding the behavior of individual cells. In the present study, we have developed single cell culture arrays using magnetic force and a pin holder, which enables the allocation of the magnetically labeled cells on arrays, and have analyzed their dynamics. The pin holder was made from magnetic soft iron and contained more than 6000 pillars on its surface. The pin holder was placed on a magnet to concentrate the magnetic flux density above the pillars. NIH/3T3 fibroblasts that were labeled with magnetite cationic liposomes (MCLs) were seeded into a culture dish, and the dish was placed over the pin holder with the magnet. The magnetically labeled cells were guided on the surface where the pillars were positioned and allocated on the arrays with a high resolution. Single-cell patterning was achieved by adjusting the number of cells seeded, and the target cell was collected by a micromanipulator after removing the pin holder with the magnet. Furthermore, change in the morphology of magnetically patterned cells was analyzed by microscopic observation, and cell spreading on the array was observed with time duration. Magnetic force-based cell patterning on cell culture arrays would be a suitable technique for the analysis of cell behavior in studies of cell-cell variation and cell-cell interactions.     

Dynamics of step bunching in heteroepitaxial growth on vicinal substrates

When a heteroepitaxial film is grown on a vicinal substrate, the terrace steps at the growth front may bunch together to relieve strain, resulting in a rough surface. On the other hand, proper manipulation of the growth kinetics may suppress the inherent bunching instability, thus preserving step-flow growth. Here we show that the step dynamics in the early stages of growth can already determine whether the bunching instability is truly suppressed, prior to bunching actually taking place in the unstable regime. We determine the critical film thickness above which steps will bunch and exploit its scaling properties and usefulness for extracting intrinsic energy parameters. Experimental studies of SrRuO(3) films grown on vicinal SrTiO(3) substrates clearly establish the existence of the critical film thickness in step bunching.     

Vibrational spectroscopy and state-specific dissociation dynamics for vinyl chloride cation in the B state

C(2)H(3)(35)Cl+ in the ground vibronic state was generated by one-photon mass-analyzed threshold ionization spectrometry, and its photodissociation in the 461-406 nm range was investigated. Ionization energy to the ground state of C(2)H(3)(35)Cl+ was 10.0062 +/- 0.0006 eV while its B state onset was higher by 2.7456 +/- 0.0003 eV. A vibrational spectrum of the cation in the B state obtained by recording the product ion yield as a function of wavelength was analyzed by referring to the quantum chemical results at the TDDFT/B3LYP/6-311++(df,pd) level. Analysis of product time-of-flight profiles recorded with different laser polarization angles showed that the dissociation pathway for the cation in the B state changed with the vibrational energy, from internal conversion to X and statistical dissociation therein to curve crossing to C and repulsive dissociation therein. B --> C curve crossing seemed to occur along a direction close to the C-Cl bond stretch.     

On the PPh3 catalyzed reaction between dibenzoylacetylene and vicinal -OH and -SH acids. One-pot synthesis of 1,3-dioxolane derivative

The efficient conjugate addition of vicinal - OH and - SH acids such as ethylene glycol and 1,2-ethanedithiol to dibenzoylacetylene in the presence of PPh3 leads to different products depending on the reaction conditions. Ab initio calculations at HF/6-31G* level shows that the unsymmetrical envelope conformation of 2,2-disubstituted 1,3-dioxolane 1 is more stable than the half-chair and Cs symmetric envelope forms.     

Anisotropic two-dimensional sheets assembled from rod-shaped metal complexes

The facile formation of anisotropic two-dimensional sheets with different sizes, ranging from nanometre-scale to micrometre-scale, was achieved by the assembly of rod-shaped palladium complexes.