Efficient synthesis and astonishing supramolecular architectures of several symmetric macrolactams

The synthesis of four C(n) symmetric macrocyclic lactams cyclo-[NH-CH(2)-CH=CH-CH(2)-CO](n) (1, n=2; 2, n=3; 3, n=4) and cyclo-[NH-CH(2)-CH(2)-CH=CH-CO](3) (4) has been achieved by two approaches. A linear route leads to precursors that are subsequently macrocyclized in a separate step. The second, convergent approach relies on the symmetry of the targets: it includes suitably activated subunits, which are subjected to macrocyclization conditions. The subunits first oligomerize, then cyclize to form either pure macrolactams or mixtures. The macrolactam units 1, 2 and 4 stack on top each other through weak interactions (hydrogen bond and van der Waals), to form endless square, rectangular and triangular prisms, respectively. These stacks are further packed side by side in crystals grown from isotropic media. The overall dipoles in the crystals from lactams 1 and 4, which result mostly from the alignment of amide groups, are zero and large, respectively. Macrolactam 2 displays an astonishing isomorphism when allowed to cool down in anisotropic liquid crystal solutions. Large hollow hexagonal tubes are then obtained through a fractal process. Contrary to the three previous rings, 3 yields crystals where prisms of any shape are absent.     

New synthesis of two tridentate bipyrazolic compounds and their cytotoxic activity tumor cell lines

Two new tripodal compounds - 4-{bis[(3,5-dimethyl-1H-pyrazole-1-yl)methyl]amino}butane-1-ol (1); ethyl 1-[((2-hydroxyethyl){[3-(ethoxycarbonyl)-5-methyl-1H-pyrazole-1-yl]methyl} amino)methyl]-5-methyl-1H-pyrazole-3-carboxylate (2) were reported. The evaluation of the cytotoxic properties in vitro of these ligands, was examined on two tumor cell lines - P815 (mastocytome murine) and Hep (carcinoma of human larynx). The concentration required to induce 50% of lysis (IC(50)) was more pronounced against P815 cell line (IC(50): 39.42 microg mL(-1) for the compound 1 and 97.74 microg mL(-1) for the compound 2) than the Hep cell line (IC(50): 83.49 microg mL(-1) for compound 1 and 185.30 microg mL(-1) for compound 2). Statistical analysis shows that the compound 1 is two to three folds more cytotoxic than the compound 2 (p < 0.05). Interestingly, the cytotoxic activity depends strongly on both the substituents linked to the aminic nitrogen and pyrazolic rings.     

Targeting DNA base pair mismatch with artificial nucleobases. Advances and perspectives in triple helix strategy

This review, divided into three sections, describes the contribution of the chemists' community to the development and application of triple helix strategy by using artificial nucleic acids, particularly for the recognition of DNA sequences incorporating base pair inversions. Firstly, the development of nucleobases that recognise CG inversion is surveyed followed secondly by specific recognition of TA inverted base pair. Finally, we point out in the last section recent perspectives and applications, driven from knowledge in nucleic acids interactions, in the growing field of nanotechnology and supramolecular chemistry at the border area of physics, chemistry and molecular biology.     

Pesticide residue levels in peppers cultivated in Souss Masa valley (Morocco) after multiple applications of azoxystrobin and chlorothalonil

Residue levels of azoxystrobin and chlorothalonil were determined in peppers grown in an experimental greenhouse. These two pesticides were selected on the basis of previous excesses of 26 and 24%, respectively, found in peppers samples cultivated in 2008 in eastern Morocco. The measurements were made over a 7 week period in which up to three successive treatments with azoxystrobin and a 4 week period in which up to three successive treatments with chlorothalonil were carried out. In all cases, plants were sprayed separately with azoxystrobin and chlorothalonil with application rates of active ingredients of 50 and 200?cc?hl^?1, respectively. Sampling was carried out at 0, 2, 4, 7, 12, 15 and 22 days for azoxystrobin and 0, 1, 3, 7, 8 and 10 days for chlorothalonil. Residue levels of azoxystrobin and chlorothalonil were determined by liquid–liquid extraction (LLE) and gas chromatography with electron-capture detector (GC-ECD). During the study, residue levels in the plantation ranged between 1.14 and 0.02?mg?kg^?1 for azoxystrobin and between 0.55 and 0.04?mg?kg^?1 for chlorothalonil. The application of an intensive washing process to the pepper samples did not lead to a significant reduction in the residue levels of either pesticide. Likewise, significant differences were not found between the residue levels in the ‘edible’ and ‘inedible’ parts of the peppers.     

Adsorption and corrosion inhibition of mild steel in hydrochloric acid solution by verbena essential oil

The inhibitive action of verbena essential oil (VEO) on the corrosion of mild Steel in 1 M HCl solutions in the temperature range 298 to 328 K was measured by use of the weight-loss method, potentiodynamic polarization, and electrochemical impedance spectroscopy. Results showed that VEO inhibited corrosion of C38 steel in 1 M HCl solution and that inhibition efficiency increased with increasing concentration of inhibitor but decreased proportionally with temperature. Potentiodynamic polarization studies suggested VEO is a mixed-type inhibitor, with the anodic type predominating. Nyquist plots were depressed semicircles with their centre below the real axis. Adsorption of VEO by the C38 steel surface followed the Langmuir adsorption isotherm. Kinetic data for dissolution were investigated.     

Studies on the inhibitive effect of potassium ferrocyanide on the corrosion of steel in phosphoric acid

In this work, the effect of potassium ferrocyanide (Pf) on the corrosion of mild steel in solutions of phosphoric acid (H₃PO₄) has been investigated in relation to the concentration of the inhibitor by weight loss, potentiodynamic polarization and AC impedance (EIS) measurements. The results obtained revealed that this compound is good a mixed-type inhibitor. The effect of temperature on the corrosion behavior with the addition of optimal concentration of Pf was studied in the temperature range 298–328 K. The value of inhibition efficiency decreases slightly with the increase in temperature. Changes in impedance parameters (charge transfer resistance, R _t, and double layer capacitance, C _dl) were indicative of adsorption of Pf on the metal surface, leading to the formation of a protective film. Adsorption of Pf on the C38 steel surface was found to obey the Langmuir adsorption isotherm. Some thermodynamic functions of dissolution and adsorption processes were also determined.     

Furan-based Polysemiacylcarbazides by Polyaddition of Bis(furanic hydrazide)s with Diisocyanates

A solution polyaddition procedure was applied to prepare furanic polyacylsemicarbazides based on 2,2′-isopropylidene-bis(5-(2-furoyl) hydrazide) and aliphatic or aromatic diisocyanates. Model compounds were prepared to facilitate the synthesis and the characterization of the polymers. A systematic study of reaction parameters (the nature of the organic phase, the temperature, the reaction time, and the concentration of monomers) was carried out. High MW polymers were obtained after 12 h reaction at 20°C with 0.2 M monomer solutions in dimethylacetamide. In fact, the polyacylsemicarbazides obtained had inherent viscosities ranging from 0.63 to 0.85 dL/g. There showed good solubility in aprotic polar solvents. The ¹H and ¹³C-NMR spectra were consistent with the expected structures. These furan-based polyacylsemicarbazides are thermally stable up to 290°C, but exhibit a complex thermal behavior. This was explained by the cyclohydration of acylsemicarbazide groups into NH-substituted oxadiazoles, resulting in rigid and high melting polymers, less stable, however, than conventional aromatic polyoxadiazoles.     

Polyterephthalates Bearing Bio-based Moieties

Dimethyl terephthalate was reacted with 5,5′-Isopropylidene-bis(ethyl 2-furoate), 1,4:3,6-dianhydrohexitols and ethan-1,2-diol in order to obtain PET incorporating bio-based moieties. Polycondensation was achieved in two steps: (i) the formation of a hydroxyethyl-terminated oligomer by reaction of starting diester mixture with excess ED and, (ii) a polycondensation step with elimination of ED was used to obtain high molar mass copolyesters. Copolymers of various compositions were synthesized and characterized by ¹H-NMR, SEC, DSC and TGA. The resulting materials are amorphous polymers (T _g = 104–127 °C) with good thermal stability.     

Quasihomogeneous Gevrey wave front and iterates of differential operators

We give a microlocal version of the theorem of the iterates for quasihomogeneous hypoelliptic operators in anisotropic Gevrey spaces.