Synthesis of Regioisomeric Functionalized Benzodifurans and Angelicins

Arenofurans have important biological and pharmacological activities. Compared to benzofurans, the reports on the synthesis of benzodifurans are rather limited. Here, we report the synthesis of a linear and an angular 3,3′‐bis(carboxymethyl)substituted benzodifuran and 4′‐carboxymethyl‐substituted angelicins from phloroglucinol, using 4‐halomethyl‐substituted dipyrones as key intermediates in the synthetic route. This strategy shows that the stability of a pyrone ring depends on the type of substituent at C(4) and the conditions used.     

N,N′‐Butane‐1,4‐diylbis­(bromo­acetamide)

The title compound, C₈H₁₄Br₂N₂O₂, lies about an inversion centre and adopts a pleated conformation, with the C(O)—NH—CH₂—CH₂ and NH—CH₂—CH₂—CH₂ torsion angles of the butane­diamine residue being −89.5 (6) and −62.1 (7)°, respectively. These data are useful in discerning the structure of polymers containing such a unit. A skew conformation is found for the Br—CH₂—C(O)—NH torsion angle [−124.2 (4)°]. The mol­ecular packing is stabilized by strong hydrogen bonds between amide groups and also by weak CH₂⋯OC inter­actions. In this way, each mol­ecule inter­acts with its six closest neighbours through eight hydrogen bonds.     

Phase and interface behaviors in type-I and type-V Lennard-Jones mixtures: theory and simulations

Density gradient theory (DGT) and molecular-dynamics (MD) simulations have been used to predict subcritical phase and interface behaviors in type-I and type-V equal-size Lennard-Jones mixtures. Type-I mixtures exhibit a continuum critical line connecting their pure critical components, which implies that their subcritical phase equilibria are gas liquid. Type-V mixtures are characterized by two critical lines and a heteroazeotropic line. One of the two critical lines begins at the more volatile pure component critical point up to an upper critical end point and the other one comes from the less volatile pure component critical point ending at a lower critical end point. The heteroazeotropic line connects both critical end points and is characterized by gas-liquid-liquid equilibria. Therefore, subcritical states of this type exhibit gas-liquid and gas-liquid-liquid equilibria. In order to obtain a correct characterization of the phase and interface behaviors of these types of mixtures and to directly compare DGT and MD results, the global phase diagram of equal-size Lennard-Jones mixtures has been used to define the molecular parameters of these mixtures. According to our results, DGT and MD are two complementary methodologies able to obtain a complete and simultaneous prediction of phase equilibria and their interfacial properties. For the type of mixtures analyzed here, both approaches have shown excellent agreement in their phase equilibrium and interface properties in the full concentration range.     

Pyrene-benzoylthiophene bichromophores as selective triplet photosensitizers

Combination of the pyrene and benzoylthiophene units constitutes an interesting approach to design bichromophoric photosensitizers with increased intersystem crossing quantum yield and enhanced selectivity. The potential of this strategy has been illustrated in the present work by using a model photoisomerization reaction.     

Synthesis of analogs of amathamide A and their preliminary antimicrobial activity

Syntheses of three non-brominated analogs of amathamide A (1), a natural alkaloid isolated from the Tasmanian marine bryozoan Amathia wilsoni, are described. Antimicrobial activity against Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Pseudomona aeruginosa, and Candida albicans was tested. Test results for amathamide A (1) showed a weak activity against C. albicans and E. coli. The three non-natural analogs 2-4 proved to be inactive compounds.     

Gradient ion-pair chromatographic method for the determination of iron N,N'-ethylenediamine-di-(2-hydroxy-5-sulfophenylacetate) by high performance liquid chromatography-atmospheric pressure ionization electrospray mass spectrometry

The most effective remedy for iron deficiency is the use of synthetic iron chelates, specifically chelates derived from polyaminecarboxylic acids as EDDHSA (N,N'-ethylenediamine-di-(2-hidroxy-5-sulfophenylacetic) acid). A gradient ion-pair chromatographic method was developed to quantify the total amount of chelated iron in EDDHSA/Fe3+ fertilizers. Two mobile phases were used containing, respectively, 35 and 75% acetonitrile in a 0.005 M tetrabutylammonium hydroxide aqueous solution at pH 6.0. The stationary phase was a reverse phase C-18 column (150mm x 3.9mm i.d., dp = 5 microm). Two chromatographic peaks appeared and were identified by Electrospray Mass Spectrometry. The first peak corresponds to the monomer of EDDHSA/Fe3+ and the second peak has been assigned to condensation molecules. Quality parameters indicate that the method is suitable for the quantification of iron chelate by EDDHSA fertilizers.     

Some issues on the calculation of interfacial properties by molecular simulation

Some of the pitfalls that may befall molecular simulations of interfaces are discussed. They are all related to the calculation of the pressure tensor profiles, which are needed in order to compute surface tensions. We focus on three controversial points: (1) the calculation of the pressure tensor profiles for polyatomic systems, in particular, when the SHAKE algorithm is employed, (2) the addition of long-range corrections to compensate the truncation of the potential, and (3) the importance of including adequate error intervals with the results. Most of the conclusions are general, but some specifically apply to multiple site molecular-dynamics simulations.     

A study of simplified molecular models in phase equilibrium prediction

Monfort, J.P. and Rojas R., M.D.L., 1978. A study of simplified molecular models in phase equilibrium prediction. Fluid Phase Equilibria, 2: 181–198.The accuracy of three molecular models of solution (Wilson, UNIQUAC and NRTL) is tested for 34 binary systems and 9 ternary systems. The aim of this paper is to attempt some evaluation of these models. Vapor-liquid calculations show a slight superiority of the UNIQUAC equation in the representation of experimental data, while liquid-liquid calculations using a method of determination of binary energetic parameters from mutual solubility data show a better prediction with the NRTL equation.     

The γ‐form of n‐eicosanol

In the crystal of the title compound, C₂₀H₄₂O, the mol­ecules are packed in layers parallel to the (100) plane. The alkyl chains are parallel to the [30] direction and these molecular chains are hydrogen‐bonded into chains parallel to the c axis. All C—C bonds of the alkyl chain show an antiperiplanar (trans) conformation, with a slight deviation from the ideal value (180°) in the C—C bonds close to the hydrogen bonds. The length of the alkyl chain is 27.92 (2) Å and the tilt angle is 59.7 (2)°.