Synthesis and characterizations of hemiditactic homopolymers derived of poly(3‐allyl‐3‐methylmalic acid): An example of a new class of polymer's ditacticity

A number of works have been focused on the study of polymers microtacticity and the probability of iso‐, syndio‐, and atactic arrangement of monomers such as polypropylene and poly(methacrylic esters) before the 1980s. This type of study was fewer in the last four decades despite the importance of stereochemical knowledge of macromolecules in the biomedical field. NMR analysis was the invaluable tool for the study of stereochemistry. This work detailed the synthesis and the physicochemical and microtacticity characterizations of new semicrystalline and amorphous polyesters, poly(3‐allyl‐3‐methylmalic acid) (PAlMMLA) derivatives which are part of the poly(malic acid) family. This polymer is biodegradable and biocompatible. It can also be chemically modified for a possible combination with bioactive molecules. It can be synthesized from chiral product leading a stereoregular and semicrystalline structure. In the case of a racemic starting product, the obtained macromolecular structure is amorphous. Semi‐crystalline polyester presented a highly diisotactic structure. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2408–2418     

Procyanidin B3 synthesis: a study of leaving group and Lewis acid activator effects upon interflavan bond formation

A range of electrophilic ethers were prepared via DDQ oxidation and alcoholic trapping (propanol, crotyl alcohol and propargyl alcohol) at the C4 position of (+)-catechin. The Lewis acid-mediated C4-substitution of each of these ethers was examined and it was found that the propargyl ether was the best overall electrophile. A range of Lewis acids were then examined as activators and it was found that BF₃·OEt₂ was the best in terms of both yield and stereochemical control at the C4 position. This newly developed set of conditions was then used to prepare the natural product nutraceutical procyanidin B3 with complete control of stereochemistry.     

Novel Antimicrobial Peptides from a Cecropin-Like Region of Heteroscorpine-1 from Heterometrus laoticus Venom with Membrane Disruption Activity

The increasing antimicrobial-resistant prevalence has become a severe health problem. It has led to the invention of a new antimicrobial agent such as antimicrobial peptides. Heteroscorpine-1 is an antimicrobial peptide that has the ability to kill many bacterial strains. It consists of 76 amino acid residues with a cecropin-like region in N-terminal and a defensin-like region in the C-terminal. The cecropin-like region from heteroscorpine-1 (CeHS-1) is similar to cecropin B, but it lost its glycine-proline hinge region. The bioinformatics prediction was used to help the designing of mutant peptides. The addition of glycine-proline hinge and positively charged amino acids, the deletion of negatively charged amino acids, and the optimization of the hydrophobicity of the peptide resulted in two mutant peptides, namely, CeHS-1 GP and CeHS-1 GPK. The new mutant peptide showed higher antimicrobial activity than the native peptide without increasing toxicity. The interaction of the peptides with the membrane showed that the peptides were capable of disrupting both the inner and outer bacterial cell membrane. Furthermore, the SEM analysis showed that the peptides created the pore in the bacterial cell membrane resulted in cell membrane disruption. In conclusion, the mutants of CeHS-1 had the potential to develop as novel antimicrobial peptides.     

Silver catalyzed C–C and C–S coupling of aryl halides and thiols with boronic acids

An efficient Ag(I) catalyzed carbon–carbon and carbon–sulfur bond formation reaction of aryl halides and thiols with boronic acids has been demonstrated. Using this protocol, substrates with a wide range of functional group including electron-rich, and electron deficient substituents have been explored. These reactions are particularly useful to prepare symmetrical and unsymmetrical biphenyls and thioethers. These products were isolated in high yield.     

An improved method of ring closing metathesis in the presence of basic amines: application to the formal synthesis of (+)-lentiginosine and other piperidines and carbamino sugar analogs

A generalized method for performing ring closing metathesis in the presence of basic amines has been established and successfully used in the formal synthesis of (+)-lentiginosine as well as some valuable intermediates for the synthesis of several other azasugars and aminocyclitols.     

Synthesis and radiopharmacological study of new metallated thiazolidines and dithioacetals of N-allyl-substituted cysteamine and methylcysteamine

New germa- and silathiazolidines or germa- and siladithioacetals with N-allyl-substituted cysteamine and methylcysteamine ligands have been synthesized and their pharmacological properties (toxicity, radioprotective activity) have been studied. A notable decrease in the toxicity and a rather large increase in the radioprotective activity of these new organometallic derivatives compared to N-allyl-substituted cysteamine and methylcysteamine were observed.     

Vapour–liquid equilibria, azeotropic data, excess enthalpies, activity coefficients at infinite dilution and solid–liquid equilibria for binary alcohol–ketone systems

Isothermal vapour–liquid equilibria (VLE), solid–liquid equilibria and excess enthalpies have been measured for the systems cyclohexanone + cyclohexanol and 2-octanone + 1-hexanol. Additionally in this paper binary azeotropic data at different pressures for 1-pentanol + 2-heptanone and 1-hexanol + 2-octanone have been determined with the help of a wire band column. Furthermore activity coefficients at infinite dilution for methanol, ethanol, 1-butanol and 1-propanol in 2-octanone at different temperatures have been measured with the help of the dilutor technique. These data together with literature data for alcohol–ketone systems were used to fit temperature-dependent group interaction parameters for the group contribution method modified UNIFAC (Dortmund) and the group contribution equation of state VTPR.     

Interfacial insights on the dibenzo-based crown ether assisted cesium extraction in [BMIM][Tf2N]–water binary system

The distribution coefficient of Cs is estimated using dibenzo-21-crown-7 (DB21C7) and di-benzo-18-crown-6 (DB18C6) in 1-butyl-3-methylimidazolium bis (trifluroromethanesulphonyl) imide (BMIMTF2N) ionic liquid by performing solvent extraction experiments. In addition, molecular dynamics studies on the extraction of cesium (Cs⁺) ion transfer from the aqueous phase to the BMIMTF2N phase is reported. The experimental findings gave a cesium distribution coefficient of 0.218 and 0.326, which agrees closely with the values of 0.2 and 0.5 obtained from MD simulation for the ionophores DB18C6 and DB21C7, respectively. Thus MD simulation may be helpful in screening the solvents prior to the experiments.

     

Colourimetric and spectroscopic discrimination between nucleotides and nucleosides using para-sulfonato-calix[4]arene capped silver nanoparticles

The complexation of nucleosides and nucleotides by hybrid nanoparticles capped by para-sulfonato-calix[4]arene shows clear discrimination between purine and pyrimidine based molecules. For the pyrimidine nucleotides there is appearance of a new absorption band around 550 nm, and a colour change from yellow to orange red and pink.