Constituents of the Leaves and Stem Bark of Aglaia foveolata

The previously known potent cytotoxic agent silvestrol (1) (0.002% w/w yield) and five new flavagline derivatives (2-6) were isolated from the leaves of Aglaia foveolata collected in Indonesia. The new compound 5 has an unprecedented cyclic amide moiety in its cyclopenta[b]benzopyran skeleton, while compound 6 is a novel benzo[b]oxepine derivative in which the oxepine ring is cleaved. Pyramidatine (7), a biogenetic precursor of the new flavaglines 2-6, was isolated from the leaf extract investigated. Silvestrol was also isolated from the stem bark of A. foveolata (yield of 0.02% w/w) along with a new baccharane-type triterpenoid (8). The structures of the new compounds were elucidated on the basis of their NMR and mass spectrometric data. All new compounds isolated were tested against a panel of cancer cell lines, but only compound 2 was cytotoxic (IC₅₀ range=1.4-1.8 μM), and is the first member of the cyclopenta[b]benzopyran class found to exhibit this type of activity. Compound 2 also showed significant NF-κB inhibitory activity in an Elisa assay (IC₅₀=0.37 μM).     

Zur Synthese und Kristallstruktur von Na10[M3O6][MO3] (M = Fe,Mn) mit einer Bemerkung zu den magnetischen Eigenschaften

Synthesis and Crystal Structure of Na₁₀[M₃O₆][MO₃] (M = Fe, Mn) with a Remark on the Magnetic Properties Single crystals of Na₁₀[M₃O₆][MO₃] (M = Mn, Fe) may be obtained via a redox reaction of CdO with the respective transition metal in the presence of Na₂O and a flux as red single crystals, which are sensitive to moisture. The crystal structure (determined from IPDS data, , Z = 6) contains isolated trigonal aplanar [MO₃] units and layers of [MO₄] tetrahedra connected via corners to three‐membered rings, which share common edges resulting in the formation of twelve‐membered rings. The statistical occupancy of 21 out of 60 sodium atoms per unit cell is discussed and calculations of the Madelung Part of the Lattice Energy (MAPLE) are given. Furthermore, we report on the magnetic properties of Na₁₀[Mn₃O₆][MnO₃] in close relation to the structural entities.     

fac-{Ru(CO)3}2+-core complexes and design of metal-based drugs. synthesis, structure, and reactivity of Ru-thiazole derivative with serum proteins and absorption-release studies with acryloyl and silica hydrogels as carriers in physiological media

The reaction of [Ru2(CO)6Cl4], 1, with excess THZ (1,3-thiazole) in absolute ethanol at 55 degrees C produces fac-[Ru(CO)3Cl2(THZ)], 2, in high yield. [Ru(CO)2Cl2(THZ)2], 3, is formed at higher temperature (ca 70 degrees C) and higher concentration of THZ. The X-ray structures of the new compounds have been determined, and density functional studies performed at the hybrid B3LYP/(Lanl2DZ, Ru; 6-311+G**, CHClNOS) level allowed the estimation of the structures of several conformers as well as that of their relative total electronic energies. Compound 2 is soluble (slowly) in aqueous media, where it reacts with the transport proteins bovine serum albumin (BSA) and human apotransferrin (HTF), and at a lower extent with calf thymus DNA (CT-DNA) and with guanosine-5'-monophosphate (GMP). The complex molecule is adsorbed by certain synthetic acryloyl polymers that have terminal carboxylate functions and is embedded in silica gels when these latter are prepared in the presence of a solution of 2. Ruthenium species are slowly released from the loaded gels into physiological solutions at pH 7.4. The reactivity of 2 with biomolecules and synthetic hydrogels makes it a compound of interest for anticancer and antimetastases tests.     

Syntheses, structures, and anion-binding properties of two novel calix[2]benzo[4]pyrroles

Calix[2]benzo[4]pyrrole m-6 and p-6, each containing two dipyrromethane moieties and two m-phenylene or p-phenylene units, respectively, were readily synthesised from pyrrole, 1,3- and 1,4-bis(1,1'-dimethylhydroxymethyl)benzene, (m-4 and p-4, respectively) and acetone. Macrocycles m-6 and p-6 were tested as receptors for a selection of anions, such as acetate, dihydrogenphosphate and fluoride. The X-ray structures of m-6 and p-6 and those of the complexes m-6F(-), m-6Cl(-) and m-6CH(3)COO(-) (with an nBu(4)N(+) counterion) were also determined.     

Diastereoselective Simmons-Smith cyclopropanations of allylic amines and carbamates

Cyclopropanation of 3-(N,N-dibenzylamino)cyclohexene with either Zn(CH(2)I)(2)(Wittig-Furukawa reagent) or CF(3)CO(2)ZnCH(2)I (Shi's reagent) gives the corresponding syn-cyclopropane as a single diastereoisomer, whilst cyclopropanation of 3-(N-tert-butoxycarbonylamino)cyclohexene with CF(3)CO(2)ZnCH(2)I gives the corresponding anti-cyclopropane exclusively; facile N-deprotection gives access to either diastereoisomer of the trifluoroacetic acid salt of 2-aminobicyclo[4.1.0]heptane.     

Influence of the R-substituents on the properties of [Ni(R2pipdt)(dmit)] complexes and crystal structure where R = CH2C6H5

[Ni(R2pipdt)(dmit)], (R2pipdt = 1,4-disubstituted-piperazine-3,2-dithione, R = CH2C6H5; dmit = 1,3-dithiole-2-thione-4,5-dithiolate) (1b) has been prepared and characterised and the properties compared with those of the known complex 2b belonging to the same class where R = Pr i. Cyclic voltammetry of 1b and 2b was carried out and compared with that of the respective R2pipdt ligand precursors (1a and 2a ). The nature of the R-groups of the pipdt ligand exerts an effect on the redox potentials and confirmed the position of the LUMO as mainly on the R2pipdt part of the complex. Accordingly the low frequency absorption, assigned to the HOMO-LUMO transition which has inter-ligand charge-transfer character, is found for 1b at lower frequency when compared to the corresponding transition of 2b. In situ EPR was carried out on electroreduced radical species of the R2pipdt ligand precursors (1a, 2a ) and corresponding complexes (1b, 2b ). This revealed considerable delocalisation of the unpaired electron on the R2pipdt ligand in 1b and 2b with coupling constants to N and H comparable with those of 1a and 2a . Complex 1b crystallised in the space group Pnma and shows an essentially planar complex (with out-of-plane R groups) pi stacked at a distance of 3.65(1) A. Such a one-dimensional structure is not achieved in the case of 2b, where the complex units are almost parallel and head-to-tail with each other forming dimers and this difference in solid-state packing is apparent in the diffuse reflectance spectrum of each. Plane-wave DFT calculations for 1b revealed a highly one-dimensional band structure with considerable band dispersion along the direction of greatest molecular interaction via pi-stacking.     

Mechanism of quinol oxidation by ferricenium produced by light excitation in reaction centers of photosynthetic bacteria

The kinetics and thermodynamics of cyclic electron transfer through the isolated reaction center protein of photosynthetic bacterium Rhodobacter sphaeroides were determined in detergent (Triton X-100) solution. The redox reactions between the reducing (ubiquinol-0 or ubiquinol-10) and oxidizing species (ferricenium, ferricytochrome, or ferricyanide) produced chemically or by light excitation of the protein were monitored by absorption changes of the reactants and by acidification of the solution accompanied with the disappearance of the quinol. The bimolecular rate constants of reactions of anionic ubiquinol-0 with different oxidizing agents showed large variation: 5 x 10(8) M(-1) s(-1) for ferricenium, 3.5 x 10(5) M(-1) s(-1) for ferricyanide, and 1.5 x 10(5) M(-1) s(-1) for ferricytochrome. Although the redox partners were created in pairs by the same protein promptly after light excitation, their bimolecular redox reaction was not observed even in the case of the fastest reacting partners of ferricenium and ubiquinol-0. Instead, they equilibrate with the corresponding (donor and acceptor) pools before the electron is transferred. The (logarithms of the) observed rate constants of quinol oxidation showed steep pH-dependence for water soluble ubiquinol-0 (slope +1) and mild pH-dependence for hydrophobic ubiquinol-10 (slope approximately 0.25). Combined with studies of the ionic strength dependence of the rate, it was concluded that the electron-transfer pathways of ubiquinol-0 and ubiquinol-10 oxidation started from their anionic and neutral forms, respectively. The mild pH-dependence of the rate of ubiquinol-10 oxidation came from the electrostatic interactions between ferricenium and the pH-dependent surface charges of the reaction center. The results help to understand, monitor, and design (cyclic) electron flow in bioenergetic proteins.     

A novel highly stereoselective synthesis of 2,3-disubstituted 3H-quinazoline-4-one derivatives

[structure: see text]. An efficient three-step synthesis of chiral 3H-quinazoline-4-one derivatives from commercial materials is disclosed. The Mumm reaction of imidoyl chloride with alpha-amino acids followed by reductive cyclization affords enantiomerically pure (ee >93%) quinazoline-4-ones in good overall yield. A comparison with existing approaches indicates that this method is superior for hindered substrates.