New di-(beta-chloroethyl)-alpha-amides on N-(meta-acylamino-benzoyl)- D,L-aminoacid supports with antitumoral activity

In order to obtain new compounds with antitumoural action the N-(meta-acylaminobenzoyl)-alpha-acylaminobenzoyl)-alpha-aminoacids 4-9 were prepared. These compounds were subsequently converted into the corresponding Delta(2)-oxazolin-5-ones 10-15, which in turn were submitted to a ring opening reaction with di-(beta-chloroethyl)amine to afford the peptide supported N-mustards 16-21, which showed low toxicity and cytostatic activity similar to that of sarcolisine against the Ehrlich ascite and Walker 253 carcinosarcoma.     

Further evidence for formation of a narrow baryon resonance with positive strangeness in K + collisions with Xe nuclei

We have continued our investigation of the charge-exchange reaction K ⁺Xe → K ⁰ pXe’ in the bubble chamber DIANA. In agreement with our previous results based on part of the present statistics, formation of a narrow pK ⁰ resonance with mass of 1537 ± 2 MeV/c ² is observed in the elementary transition K ⁺ n → K ⁰ p on a neutron bound in the xenon nucleus. The visible width of the peak is consistent with being entirely due to instrumental resolution and allows one to place an upper limit on its intrinsic width: Γ < 9 MeV/c ². A more precise estimate of the resonance intrinsic width, Γ = 0.36 ± 0.11 MeV/c ², is obtained from the ratio between the numbers of resonant and nonresonant charge-exchange events. The signal is observed in a restricted interval of incident K ⁺ momentum that is consistent with smearing of a narrow pK ⁰ resonance by Fermi motion of the target neutron. The statistical significance of the signal is some 7.3, 5.3, and 4.3 standard deviations for the estimators and , respectively. This observation confirms and reinforces our earlier results, and offers strong evidence for formation of a pentaquark baryon with positive strangeness in the charge-exchange reaction K ⁺ n → K ⁰ p on a bound neutron. (The DIANA Collaboration) The text was submitted by the authors in English.     

Macrolides from the scent glands of the tropical butterflies Heliconius cydno and Heliconius pachinus

The four major components present in scent gland extracts of the male Costa Rica longwing butterflies Heliconius cydno and Heliconius pachinus were identified as 12- and 14-membered macrolides containing a C(18)-carbon skeleton. By use of micro-reactions and spectrometric examinations, structural proposals were made and subsequently proven by synthesis, using ring-closing-metathesis as the key steps. These macrolides, (9Z,11E,13S)-octadeca-9,11-dien-13-olide (5, S-coriolide), (9Z,11E,13S,15Z)-octadeca-9,11,15-trien-13-olide (6), (9Z,13S)-octadec-9-en-13-olide (13), and (9Z,11S)-octadec-9-en-11-olide (25), are biosynthetically obviously derived from oleic, linoleic, and linolenic acids. Their absolute configurations were determined by gas chromatographic investigations on chiral phases, showing all to possess (S)-configuration.     

New anionic cobalt complexes using highly hindered bis-amides with varying donor abilities as ligands

Four potential tetradentate ligands of formulae 1,2-bis-(3,5-di-tert-butyl-2-hydroxybenzamido)ethane (H(4)L(1), 1), 1,2-bis-(3,5-di-tert-butyl-2-hydroxybenzamido)propane (H(4)L(2), 2), 1,2-bis-(3,5-di-tert-butyl-2-hydroxybenzamido)benzene (H(4)L(3), 3) and 1,8-bis-(3,5-di-tert-butyl-2-hydroxybenzamido)naphthalene (H(4)L(4), 4) have been prepared and the crystal structures of three of them (1, 3 and 4) determined by single crystal X-ray diffraction. The investigation of their complexing ability toward Co(II) afforded the compounds of formulae [Co(III)(L(3))Na(I)(H(2)O)(2)] (5), [Co(III)(L(n))Li(I)(H(2)O)2] with n = 1 (6), 2 (7) and 3 (8) and [Co(II)(L(4))Li(I)(2)] (9). Complexes 5-8 are square planar Co(III) species, as corroborated by the crystal structure of 5. In this compound, two amide-nitrogen and two phenolate-oxygen atoms of a fully deprotonated (L(3))(4-) anion build a slightly distorted square planar surrounding around the cobalt atom, the Co-N distances [1.858(3) and 1.861(3) A] being somewhat longer than the Co-O ones [1.798(3) and 1.801(3) A]. Magnetic and 1H NMR data at room temperature for 6-8 support the occurrence of an intermediate S = 1 low-lying state for the Co(III) center which is stabilized by the strong donating ability of the fully deprotonated bis-amidate ligands. In the case of the compound with the naphthalene derivative (9), the analytical and spectroscopic data suggest the occurrence of a low spin Co(II) complex. The weakening of the ligand field strength of the tetradentate bis-amidate ligand in the naphthalene derivative (5-6-5 ring-membered fused chelate) when compared to the situation in complexes 5-8 (5-5-5 ring-membered fused chelate) would account for this feature.     

Modulation of cross polarization in motionally averaged solids by Variable Angle Spinning NMR

In systems where the dipolar couplings are partially averaged by molecular motion, cross-polarization is modulated by sample spinning. The cross-polariation efficiency in Variable Angle Spinning (VAS) and Switched Angle Spinning (SAS) experiments on mobile samples is therefore strongly dependent on the spinning angle. We describe simulations and experimental measurements of these effects over a range of spinning angles from 0° to 90°.     

Submicron foaming in gelatine by nanosecond and femtosecond pulsed laser irradiation

We compare the foaming characteristics induced by irradiation with single ns and fs laser pulses of UV, VIS and IR wavelengths on gelatines differing in gel strength (bloom values 75 and 225) and in crosslinking degree. We have observed that while laser irradiation with nanoseconds leads to the formation of a microfoam layer at 266 nm, and melting and crater formation at longer wavelengths (532 and 1064 nm), fs pulse irradiation leads to submicron foaming at all wavelengths studied (266, 400 and 800 nm). These results show the possibility of controlling the submicrometric foam structure in this biomaterial and can shed light into the working mechanisms of fs laser nanoprocessing in biomaterials, where increase of temperature, thermoelastic stress generation, and stress-induced bubble formation are mediated by the generated plasma.     

All-cis-1,2,3,4,5,6-cyclohexanehexacarboxylate two-dimensional gadolinium(III) complexes: Synthesis,X-ray crystal structure and magnetic properties

The first gadolinium(III) complexes with the trideprotonated form of the 1,2,3,4,5,6-cyclohexanehexacarboxylic acid (H₃clhex³⁻) of formulae [Gd(H₃clhex)(H₂O)₄]_n·3nH₂O (1) and [Gd(H₃clhex)(H₂O)₄]_n·6nH₂O (2) have been prepared through the gel technique and their structures determined by single crystal X-ray diffraction. The structure of 1 is made up of 6³ honey-comb layers which are generated by [Gd(H₂O)₄]³⁺ cations and H₃clhex³⁻ anions acting as three-fold nodes and three-fold connectors, respectively. The structure of 2 consists of a [4⁴,6²] two-dimensional network extended in the ac plane where the H₃clhex⁻³ groups act as four-fold connectors and the [Gd(H₂O)₄]³⁺ units as four-fold nodes. Compound 1 crystallises in a non-centrosymmetric space group P2₁. Its absolute structure could be determined reliably, indicating the spontaneous resolution of a homochiral crystal and the freezing of one of the conformations of the all-cis H₃clhex⁻³ ligand. Compound 2 crystallises in the P2₁/n space group, the presence of an inversion centre making both conformations to occur. 1 and 2 are different solvates of the same system, the latter one synthesised under a higher pH value of the gel than the former. The investigation of the magnetic properties of 1 and 2 in the temperature range 1.9–300 K reveals a Curie law behaviour for the two compounds.     

Structure,microstructure and optical properties of cerium oxide thin films prepared by electron beam evaporation assisted with ion beams

Cerium oxide thin films were prepared by combined electron beam evaporation and ion beam assisted deposition techniques (EBE–IBAD). Their crystallographic structures, microstructures, and optical properties were studied as a function of the substrate temperature (200 °C and 500 °C) and the dose of Ar⁺ or O₂⁺ ion assistance during growth. X-ray diffraction was used to estimate the crystallographic texture, grain size, microstrain and lattice constant. Sample microstructure was studied by scanning electron microscopy. Transmission UV–vis spectroscopy was employed to obtain optical information (band gap, density, and refractive index). All films showed a cubic CeO₂ structure with different preferential growth depending on the preparation conditions. The bombardment with Ar⁺ ions during film deposition proved to be very effective for changing the film structure, hindering columnar growth and producing smaller grain sizes and higher values of microstrain and lattice constant. Films grown at 200 °C and Ar⁺ ion assistance showed the highest density, the smallest grain size (～10 nm) and a high expansion of the lattice constant (up to ～1%). This expansion is related to the presence of Ce³⁺ at the grain boundaries. Ion assistance during the growth leads to films with higher values of refractive index and lower values of band gap.     

Pentacyanido(L)ferrate(III) complexes: Crystal structures, electrochemical and DFT studies (L = pyrazine, 4,4′-bipyridine, azide)

The crystal structures of two pentacyanido(L) ferrate(III) complexes, [P(C₆H₅)₄]₂[Fe(CN)₅(prz)]·4H₂O 1, [P(C₆H₅)₄]₂[Fe(CN)₅(4,4′-bipy)]·3H₂O 2, have been solved. Within the two complex anions the iron atoms are hexacoordinated by five cyanido ligands, the sixth position being occupied by the nitrogen atom arising from pyrazine and, respectively, 4,4′-bipyridine. The electrochemical properties of compounds 1, 2 and of the azido derivative, (Ph₄As)₂[Na(H₂O)₄][Fe(CN)₅(N₃)] 3, have been investigated by cyclic voltammetry. A relatively complicated redox behavior of these complexes was found, due especially to the electron transfer involving the central metallic ion that changes reversibly its oxidation state (Fe^III/Fe^II redox site) and also to the coligand (4,4′-bipyridine, pyrazine or azide) which intervenes in a distinct electron transfer. The experimental data have been rationalized through DFT calculations.