Trypanocidal terpenoids from Laurus nobilis L

Trypanocidal constituents of dried leaves of Laurus nobilis L. (Lauraceae) were examined. Activity-guided fractionation of the methanol extract resulted in the isolation of two guaianolides, dehydrocostus lactone (1) and zaluzanin D (2), and a new p-menthane hydroperoxide, (1R,4S)-1-hydroperoxy-p-menth-2-en-8-ol acetate (3). The minimum lethal concentrations of these compounds against epimastigotes of Trypanosoma cruzi were 6.3, 2.5, and 1.4 microM, respectively.     

Ruthenium-catalyzed hydrosilylation of 1-alkynes with novel regioselectivity

[reaction: see text] A ruthenium catalyst precursor bearing a bulky and electron-donating pentamethylcyclopentadienyl (Cp) ligand, typically CpRuH3(PPh3), mediates hydrosilylation of several 1-alkynes with novel regioselectivity to give preferentially 2-silyl-1-alkenes.     

Kondo effect in a quantum antidot

We report Kondo-like behavior in a quantum antidot (a submicron depleted region in a two-dimensional electron gas) in the quantum-Hall regime. When both spins of the lowest Landau level are present all around the antidot, the resonances between extended edge states via antidot bound states show an abnormal feature in alternate Coulomb-blockaded regions. The feature becomes suppressed when the temperature or source-drain bias is raised as for Kondo resonances in quantum dots. Although the exact mechanism is unknown, Kondo-like correlated tunneling may arise from a Skyrmion-type edge reconstruction. This observation demonstrates the generality of the Kondo phenomenon.     

Phase transition of Ta2NiO6 with the trirutile-type structure under high pressure and high temperature

High-pressure phase transition of Ta₂NiO₆ with the trirutile-type structure was investigated from the viewpoint of crystal chemistry. A new quenchable high-pressure phase was found in the pressure range higher than 7 GPa and 900°C. The high-pressure phase has an orthorhombic cell (a=4.797(1) Å, b=5.153(2) Å and c=14.85(1) Å and space group; Abm2), and it is more dense by 9.6% than the trirutile-structured phase. Infrared spectra of the trirutile-type phase and the high-pressure phase show that Ni²⁺ ions in the high-pressure phase are still in octahedral sites. The crystal structure of the high-pressure phase is considered as a cation-ordering trifluorite-type structure, which can be stabilized by a crystal field effect of Ni²⁺ ions.     

New bis- and tris-annulation reagents for the syntheses of CD rings of steroids,bearing a functionalized 18-methyl group,by the palladium-catalyzed cyclization

2-Substituted 2-alkoxycarbonyl-3-vinylcyclopentanones (2), easily prepared by the palladium-catalyzed cyclization of 2-substituted 3-oxo-8-phenoxy-6-octenoates (1), are very suitable building blocks for CD rings of steroids, bearing particularly a functionalized 18-methyl group.     

Further evidence for the intramolecular charge-transfer interaction between tropylium ion and remote benzene rings in 9,10-dihydro-9,10-(1,2-tropylio)anthracene tetrafluoroborate and its methyl derivatives

A series of 9,10-dihydro-9,10-(1,2-tropylio)anthracene tetrafluoroborates

has been prepared. The intramolecular charge-transfer interactions in

were confirmed by their UV spectra and pK_R+ values. As a model compound 1,2,3,4-tetrahydro-1,4-(1,2-tropylio)naphthalene tetrafluoroborate ($\text{5}$)_was also examined.     

Prostaglandin analogs modified at the 10 and 11 positions

A simplified methodology for the building of prostaglandins substituted at the 10 and 11 positions is presented.     

Spontaneous formation of cadmium hydroxide nanostrands in water

Cadmium hydroxide nanostrands with a diameter of 1.9 nm were spontaneously formed by raising the pH of a dilute Cd(NO3)2 solution. The length reaches a few micrometers and the aspect ratio exceeds 1000. The crystallographic structure was successfully elucidated by high-resolution electron microscopy. The surface of the nanostrands was remarkably positively charged and adsorbed an astonishing number of negatively charged dye molecules.     

Asymmetric synthesis of functionalized aza-cyclic amino acids with quaternary stereocenters by a phase-transfer-catalyzed alkylation strategy

[Reaction: see text] Practical asymmetric synthesis of functionalized aza-cyclic alpha-amino acid derivatives possessing quaternary stereocenters has been achieved by the phase-transfer-catalyzed alkylation of 2 or 3 using chiral quaternary ammonium bromide 1 as catalyst. Subsequent reduction and alkylation of the 3-keto carbonyl moiety of 4 proceeded with complete diastereochemical control to afford the corresponding beta-hydroxy aza-cyclic alpha-amino acid derivatives having stereochemically defined consecutive quaternary carbon centers.