Interfacial properties and thermal stability of modified poly(m‐phenylene isophthalamide) thin films

Poly(m‐phenylene isophthalamide) (PMIA) is a resistant to high temperatures and chemically stable engineering material. The application as coatings and membranes, however, is limited by its poor interaction with other materials. In this report, we describe the molecular modification of PMIA through reaction with dimsyl sodium and 2‐iodine‐1‐ethanol. The substitution of 58% of amide hydrogen by ethanol (etOH) groups produces a material (MPMIA) able to develop regularly structured films on silicon substrate. The morphology of the films is dependent on the ionic strength of the precursory solution. MPMIA starts a degradation process by losing the etOH group. MPMIA has a better affinity with poly(p‐cresolformaldehyde) than with a pristine one, increasing the range of composition in which thermal stability and miscibility are observed. Thin films of these blends have different morphologies that vary from nanometric porous to two‐phase microstructured grains, according to the composition. Copyright © 2012 John Wiley & Sons, Ltd.     

Aromatic garlands,as new foldamers,to mimic protein secondary structure

Proteins modulate the majority of all biological functions and are composed of highly organized secondary structural elements such as helices, turns, and sheets. Many of these functions are affected by a small number of key structural element, protein–protein interactions. Their mimicry by peptide and non-peptide scaffolds has become a major focus of contemporary research. This paper examines oligomeric system as new foldamers, which either reproduce the local topography of the helix, or project appropriately functionality in a similar manner to residues of an alpha-helix.     

Studies on the Imide-Amide Rearrangement of Cyclic Phosphorimidates

Abstract

The imide-amide rearrangement of cyclic phosphorirnidates 1 leads to the formation of phosphoramidates 3, either thermally (> 180°C) or by the action of a Lewis acid (BF₃ OEt₂, 60°C)¹. In an attempt to develop a synthetic pathway to β aminoalcohols based on this rearrangement, we have thoroughly studied the influence of the structure of the reactants on the Lewis acid catalysed rearrangement. This study brought some insight into the mechanism of this particular reaction, namely the identification of a new polymeric structure 2. not yet described, which is converted into 3 by thermolysis². The formation of 2 at rt was followed by ³ P NMR. In the case of R′? Ph, the reactivity observed for R₂N was: i-Pr₂N > Pyrrolidine > n-Bu²N For R²=i-Pr₂, the observed R′ group effect was: Bn > 4-NO₂Bn > Ph. No reaction was observed for R′ ? Ts, n-Oct. In the case of the groups R′ ? Bn and R₂=i Pr₂ the Lewis acid effect was also studied: BF₃OEt₂, BF₃MeOr-Bu, Sc(OTf)₃ or CITi(Oi-Pr)₃ or Me₂SnCl₂.     

Molecular recognition of guanosine and 2-acetylaminofluorene-modified guanosine. A comparative study

Abstract

The ability of an abiotic receptor, 7-acetylamino-2-methyl–1,8-naphthyridine, to bind to guanosine was analysed by a combination of NMR determinations and molecular modeling studies. The results indicate that this receptor simulates the base-pairing properties of cytidine in its Watson-Crick interaction with guanosine. Binding of the same receptor to N-(guanosin-8-yl)-2-acetylaminofluorene, the guanosine adduct containing the carcinogen 2-acetylaminofluorene, was found to occur in a similar manner. The calculated binding energies show that the molecular recognition of the adduct is lower than that of the unmodified guanosine. The theoretical studies suggest that the predominance of an abnormal low energy syn conformation for the adduct is the main structural feature accounting for the observed decrease of the host-guest interaction.     

Focused microwave irradiation-assisted synthesis of N-cyclohexyl-1,2,4-oxadiazole derivatives with antitumor activity

A facile synthesis of 3,5-disubstituted 1,2,4-oxadiazole derivatives under focused microwave irradiation (FMWI) is reported. Arylamidoximes 1a–i and dicyclohexylcarbodiimide (DCC) were carried out in DMF under FMWI to obtain 1,2,4-oxadiazoles 2a–i in 61–81% yields. All compounds exhibited antiproliferative activities in vitro against three human cancer cell lines HCT-116, PC-3, and SNB-19.     

Tellurium in organic synthesis: the enantioselective synthesis of the pheromone blend components of Mayetiola destructor,Drosophila mulleri and Contarinia pisi

The components of the pheromone blend of Mayetiola destructor, Drosophila mulleri, and Contarinia pisi were synthesized in high enantiomeric excess (99% ee) from a common enantiopure dianion prepared from an enantiopure hydroxytelluride.     

1H and 13C NMR spectral data of bioactive cage‐like polycyclic compounds

Bioactive cage‐like polycyclic compounds have attracted the attention of several research groups because of their unique appearance and their biological activities. Their structures were established on the basis of ¹H NMR and ¹³C NMR spectroscopic data. The ¹H and ¹³C signal assignments and most homonuclear hydrogen coupling constants were assigned by use of techniques such as 1D ¹H and ¹³C NMR and 2D gCOSY, non‐edited gHSQC and gHMBC. The gNOESY experiments proved the endo‐stereochemistry. Copyright © 2010 John Wiley & Sons, Ltd.