AN INEXPENSIVE STIRRING DEVICE FOR THE 'MERRY-GO-ROUND' PHOTOREACTOR FOR THE DETERMINATION OF REACTION QUANTUM YIELDS

A simple bar magnet is employed to effect stirring of the contents of reaction cells in a'merry-go-round'photoreactor.     

Microwave-assisted solid-phase synthesis of peptoids

Microwave irradiation reduces the reaction time for the solid-phase synthesis of peptoids. Under these conditions, coupling of each residue requires only 1 min. The purity and yields of peptoids synthesized in this way are as good as or better than those achieved using standard methods. [reaction: see text]     

Rationalizing the generation of broad spectrum antibiotics with the addition of a positive charge

Antibiotic resistance of Gram-negative bacteria is largely attributed to the low permeability of their outer membrane (OM). Recently, we disclosed the eNTRy rules, a key lesson of which is that the introduction of a primary amine enhances OM permeation in certain contexts. To understand the molecular basis for this finding, we perform an extensive set of molecular dynamics (MD) simulations and free energy calculations comparing the permeation of aminated and amine-free antibiotic derivatives through the most abundant OM porin of E. coli, OmpF. To improve sampling of conformationally flexible drugs in MD simulations, we developed a novel, Monte Carlo and graph theory based algorithm to probe more efficiently the rotational and translational degrees of freedom visited during the permeation of the antibiotic molecule through OmpF. The resulting pathways were then used for free-energy calculations, revealing a lower barrier against the permeation of the aminated compound, substantiating its greater OM permeability. Further analysis revealed that the amine facilitates permeation by enabling the antibiotic to align its dipole to the luminal electric field of the porin and form favorable electrostatic interactions with specific, highly-conserved charged residues. The importance of these interactions in permeation was further validated with experimental mutagenesis and whole cell accumulation assays. Overall, this study provides insights on the importance of the primary amine for antibiotic permeation into Gram-negative pathogens that could help the design of future antibiotics. We also offer a new computational approach for calculating free-energy of processes where relevant molecular conformations cannot be efficiently captured.

A rapid pathway sampling method combining Monte Carlo and graph theory, developed to describe permeation pathways through outer membrane porins, can distinguish between structurally similar analogs with different permeabilities.     

Three bis‐ortho‐diynyl­arenes (BODA)

The molecule of 3,3′,4,4′‐tetrakis­(phenyl­ethynyl)­bi­phenyl, C₄₄H₂₆, is approximately planar and is located on a crystallographic inversion center. Bis­[3,4‐bis­(phenyl­ethynyl)­phenyl] ether, C₄₄H₂₆O, has mol­ecules located on twofold symmetry axes, whereas the molecule of 2,2‐bis­[3,4‐bis­(phenyl­ethynyl)­phenyl]­propane, C₄₇H₃₂, does not exhibit any molecular symmetry.     

Synthesis and characterization of novel functional poly(vinyl alcohol-co-styrene sulfonic acid) copolymers

This paper first time reports the preparation of random anionic copolymers from vinyl acetate (VAc) bearing electro-donating substituent and sodium 4-vinylbenzenesulfonate (SSA) having electro-withdrawing substituent. Copolymers (PVA-co-SSA) of different composition have been successfully prepared by a simple free radical solution polymerization technique. Resulting final copolymer contained neutral hydrophilic as well as ionizable ion exchange sites. Evaluation of spectral data obtained from Fourier transform Infrared spectroscopy, Raman spectroscopy, and ¹H Nuclear magnetic resonance helped in identifying and confirming the chemical structure of copolymers. Characterization of copolymers by gel permeation chromatography revealed high molecular weight with moderate polydispersity index. Analysis of thermal stability and glass transition temperature of copolymers by thermogravimetric analysis and differential scanning calorimetry were found in between corresponding homopolymers. Physicochemical properties of PVA-co-SSA can be beneficial for prospective advanced application in the niche area of smart membrane technology for energy and environment.     

Thermal decomposition paths in A<Subscript>2</Subscript>CuCl<Subscript>4</Subscript> complexes: anilinium and its derivatives

The thermal decomposition paths of anilinium, 4-chloro anilinium tetrachlorocopper(II) complexes are compared to their benzilinium derivative. All these complexes crystallize in the layered structure, typical for a A₂MX₄ family, are studied in literature for their magnetic, semiconducting properties. TG analyses of (anilinium)₂CuCl₄ (A) and (4-chloro anilinium)₂CuCl₄ (B) loses one molecule of organic ammonium hydrochloride along with one molecule of amine, to form (H)CuCl₃, which subsequently completely decomposes to Cu above 500 °C. On the other hand, (benzilinium)₂CuCl₄ (C) loses two molecules of hydrochloride along with chlorine molecule first then two molecules of benzyl amine with formation of Cu above 300 °C. DSC studies on C have shown reversible endothermic phase transition at 130.95 °C (−1.98 J g⁻¹) while heating and exothermic phase transition at 117.07 °C (0.93 J g⁻¹) while cooling. Thus, the observed changes in the decomposition pathway can be correlated to the order–disorder phase transition occurred in the compound C.     

A Facile Synthesis of 7,8-DI Aryl Coumarino and Flavano Benzo-Thiophenes

The key step for the synthesis of 7-hydroxy 2,3-diarylsubstituted benzothiophenes 5a-f , by starting from substituted 2-aryl-2-((2-methoxy phenyl)thio)acetophenones 3a-f as an intermediate, consists of a Friedel-Crafts cyclization followed by demethylation by Lewis acids like BF 3 OEt 2 and AlCl 3 in DCM.     

PCC-Promoted Dehydration of Aldoximes: A Convenient Access to Aromatic,Heteroaromatic, and Aliphatic Nitriles

A simple and convenient procedure for the synthesis of nitriles by dehydration of aldoximes using a PCC (pyridiniumchlorochromate) has been developed. A variety of aromatic, heteroaromatic, and aliphatic aldoximes are converted.

Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the full spectral details.