Dehydrogenative condensation of monohydrosilanes yielding disilanes in the presence of platinum complex catalysts

Dimethylphenylsilane was catalytically dehydrogenated and condensed in the presence of platinum complexes to give 1,1,2,2-tetramethyl-1,2-diphenyl-disilane.     

Oxidative addition of C-H bonds to RhCl(PMe3)3: relevant to the catalytic transformation of hydrocarbons

RhCl(PMe3)3 (1) reacts with benzene under irradiation to give the oxidative addition product, Rh(C6H5)(H)Cl(PMe3)3 (2). The reaction is promoted under CO2 atmosphere. The structure of 2 was fully characterized by X-ray crystallography as well as NMR, IR, and elemental analysis. The adduct (2) is unstable in solution even at room temperature to regenerate benzene and 1. The thermolysis of 2 under a CO atmosphere produces benzaldehyde along with the reductive elimination product, benzene. On the other hand, the prolonged photoreaction of 1 with benzene under CO2 resulted in the activation of the C-H bond and CO2 to yield Rh(C6H5)(eta2-CO3)(PMe3)3 (3).     

Stability of phosphines under hydroformylation conditions

Phosphorus-carbon bonds of p-substituted triphenylphosphines were found to be cleaved under hydroformylation conditions in the presence of a rhodium, ruthenium, or cobalt carbonyl. Only p-isomers of the decomposition products (substituted benzaldehyde, benzyl alcohol, and/or biphenyl) were formed. The ability of metal carbonyls to cleave the PC bonds was Rh > Co > Ru. Tributylphosphine was stable under the conditions. The stability of metal carbonyl-phosphine catalyst systems was also examined and compared with the extent of PC bond cleavage.     

Multi-step application of immobilized reagents and scavengers: a total synthesis of epothilone C

The total synthesis of the cytotoxic antitumour natural product epothilone C has provided a stage for the exploitation and further development of immobilized reagent methods. A stereoselective convergent synthetic strategy was applied, incorporating polymer-supported reagents, catalysts, scavengers and catch-and-release techniques to avoid frequent aqueous work-up and chromatographic purification.     

Diels-Alder reaction using a dendritic copper(II) triflate-catalyst: a positive dendritic effect on the chemical yield

A series of dendritic ligands with a 2,2′-bipyridine core was synthesized through the coupling of 4,4′-dihydroxy-2,2′-bipyridine with poly(arylether) dendron in fair yields. The corresponding copper(II) trifluoromethanesulfonate (triflate) dendrimers were applied as a Lewis acid catalyst to the Diels-Alder reaction. A positive dendritic effect on the chemical yields of adducts was observed.     

The conformational features of palytoxin in aqueous solution

Conformational features of palytoxin and acetylated palytoxin were investigated by detailed analyses of NOESY spectra. The conformational differences between palytoxin and acetylated palytoxin may account for the difference in the assembly state of palytoxin, which exists as an associated dimer, and the acetylated derivative, which exists as a monomer in aqueous solution. Two palytoxin units in the dimer may come in contact with each other at the hydrophobic region (C21-40) and the region around two conjugated double bonds (C60-84). The amino group of palytoxin is important for biological activities via Na/K ATPase, but it was not found to be involved in the contact faces of the two palytoxin units. This information should aid in revealing how palytoxin interacts with Na/K ATPase.     

Coordination complex between haemin and parallel-quadruplexed d(TTAGGG)

Haemin, iron(III)-protoporphyrin IX complex, and parallel-quadruplexed d(TTAGGG) have been shown to form a stable coordination complex which exhibits spectroscopic properties remarkably similar to those of haemoproteins.     

Amdigenols E and G,long carbon-chain polyol compounds,isolated from the marine dinoflagellate Amphidinium sp.

The novel polyol compounds, amdigenols E and G, were isolated from the dinoflagellate Amphidinium sp. that was found to adhere to the surface of the marine alga Digenea simplex. The structures of the two amdigenols were elucidated by NMR spectroscopy and ESI–CID-MS/MS analyses. Both amdigenols E and G shared partial structures with amdigenol A. Amdigenols E and G inhibited N-type Ca²⁺ channel-opening.     

Loading effects of silver oxides upon generation of reactive oxygen species in semiconductor photocatalysis

Superoxide anion radical (O(2)(-*)) and OH radical generations in suspensions of Ag metal-, Ag(2)O-, or AgO-loaded TiO(2) and BiVO(4) photocatalysts in alkaline conditions (pH 12.0) were examined by means of a luminol chemiluminescence (CL) technique and a spin-trapping fluorescence one in which terephthalic acid reacts with an OH radical to afford the highly fluorescent 2-hydroxyterephthalic acid (TAOH), respectively. The observed luminol CL intensity was remarkably enhanced by the AgO loading on TiO(2) as well as BiVO(4). This can be explained by enhancement of O(2)(-*) production on the AgO-loaded photocatalysts caused by the synergetic effects on the thermocatalytic activity upon the AgO surface and the efficient electron-hole separation at the photocatalyst/AgO interface. On the other hand, loading effects of AgO on the TAOH formation were not so significant compared to those on the CL observation, though the TAOH formation rates for the TiO(2) samples were much larger than those for the BiVO(4) ones by about three orders of magnitude. The properties of O(2)(-*) and OH radical generations on these photocatalysts are discussed on the basis of the luminol CL kinetics and approximate band edge positions of TiO(2), BiVO(4), and silver oxides.