New Synthesis of Diazepino[3,2,1‐ij]quinoline and Pyrido[1,2,3‐de]quinoxalines via Addition–Elimination Followed by Cycloacylation

This paper describes a convenient and efficient synthesis of new fused tricyclic diazepino[3,2,1‐ij]quinolines and substituted pyrido[1,2,3‐de]quinoxalines. o‐Phenylenediamines are transformed in the tricycle nucleus in only a few‐step synthetic sequence to produce ethyl 2,8‐dioxo‐1,2,3,4‐tetrahydro‐8H [1,4]diazepino[3,2,1‐ij]quinoline‐7‐carboxylate, ethyl 8‐oxo‐1,2,3,4‐tetrahydro‐8H‐[1,4]diazepino[3,2,1‐ij]quinoline‐7‐carboxylate and ethyl 2,7‐dioxo‐2,3‐dihydro‐1H,7H‐pyrido[1,2,3‐de]quinoxaline‐6‐carboxylate. The method is economical and simple to perform.     

Coordination properties of new bis(1,4,7-triazacyclononane) ligands: a highly active dizinc complex in phosphate diester hydrolysis

The synthesis and characterization of three new bis([9]aneN(3)) ligands, containing respectively 2,2'-bipyridine (L(1)), 1,10-phenanthroline (L(2)), and quinoxaline (L(3)) moieties linking the two macrocyclic units, are reported. Proton binding and Cu(II), Zn(II), Cd(II), and Pb(II) coordination with L(1)-L(3) have been studied by potentiometric titrations and, for L(1) and L(2), by spectrophotometric UV-vis measurements in aqueous solutions. All ligands can give stable mono- and dinuclear complexes. In the case of L(1), trinuclear Cu(II) complexes are also formed. The stability constants and structural features of the formed complexes are strongly affected by the different architecture and binding properties of the spacers bridging the two [9]aneN(3) units. In the case of the L(1) and L(2) mononuclear complexes, the metal is coordinated by the three donors of one [9]aneN(3) moiety; in the [ML(2)](2+) complexes, however, the phenanthroline nitrogens are also involved in metal binding. Finally, in the [ML(3)](2+) complexes both macrocyclic units, at a short distance from each other, can be involved in metal coordination, giving rise to sandwich complexes. In the binuclear complexes each metal ion is generally coordinated by one [9]aneN(3) unit. In L(1), however, the dipyridine nitrogens can also act as a potential binding site for metals. The dinuclear complexes show a marked tendency to form mono-, di-, and, in some cases, trihydroxo species in aqueous solutions. The resulting M-OH functions may behave as nucleophiles in hydrolytic reactions. The hydrolysis rate of bis(p-nitrophenyl)phosphate (BNPP) was measured in aqueous solution at 308.1 K in the presence of the L(2) and L(3) dinuclear Zn(II) complexes. Both the L(2) complexes [Zn(2)L(2)(OH)(2)](2+) and [Zn(2)L(2)(OH)(3)](+) and the L(3) complex [Zn(2)L(3)(OH)(3)](+) promote BNPP hydrolysis. The [Zn(2)L(3)(OH)(3)](+) complex is ca. 2 orders of magnitude more active than the L(2) complexes, due both to the short distance between the metal centers in [Zn(2)L(3)(OH)(3)](+), which could allow a bridging interaction of the phosphate ester, and to the simultaneous presence of single-metal bound nucleophilic Zn-OH functions. These structural features are substantially corroborated by semiempirical PM3 calculations carried out on the mono-, di-, and trihydroxo species of the L(3) dizinc complex.     

Anti-Multiple Myeloma Potential of Secondary Metabolites from Hibiscus sabdariffa—Part 2

Multiple Myeloma (MM) is an aggressive tumor causing millions of deaths every year and currently available therapies are often unsuccessful or correlated with severe side effects. In our previous work we demonstrated that the Hibiscus sabdariffa hydroalcoholic extract inhibits the growth of the MM cell line and we isolated two metabolites responsible for the activity: Hib-ester and Hib-carbaldehyde. Herein we report their interaction with proteasome, one of the main targets in the fight against MM. The molecular modelling study outlined a good interaction of both compounds with the target and these results prompted us to investigate their potential to inhibit proteasome. Metabolites were then isolated from the calyces and an extract with a high content of Hib-ester and Hib-carbaldehyde was prepared. An anticancer profile was drawn, evaluating apoptosis, autophagy and proteasome inhibition, with the anticancer properties being mainly attributed to the Hib-ester and Hib-carbaldehyde, while the proteasome inhibition of the extract could also be ascribed to the presence of anthocyanins, a class of secondary metabolites already known for their proteasome inhibitory activity.     

Green Deep Eutectic Solvents for Microwave-Assisted Biomass Delignification and Valorisation

Aiming to fulfil the sustainability criteria of future biorefineries, a novel biomass pretreatment combining natural deep eutectic solvents (NaDESs) and microwave (MW) technology was developed. Results showed that NaDESs have a high potential as green solvents for lignin fractionation/recovery and sugar release in the following enzymatic hydrolysis. A new class of lignin derived NaDESs (LigDESs) was also investigated, showing promising effects in wheat straw delignification. MW irradiation enabled a fast pretreatment under mild condition (120 °C, 30 min). To better understand the interaction of MW with these green solvents, the dielectric properties of NaDESs were investigated. Furthermore, a NaDES using the lignin recovered from biomass pretreatment as hydrogen bond donor was prepared, thus paving the way for a “closed-loop” biorefinery process.     

Comparative analysis of the performance of commonly available density functionals in the determination of geometrical parameters for zinc complexes

A set of 44 Zinc‐ligand bond‐lengths and of 60 ligand‐metal‐ligand bond angles from 10 diverse transition‐metal complexes, representative of the coordination spheres of typical biological Zn systems, were used to evaluate the performance of a total of 18 commonly available density functionals in geometry determination. Five different basis sets were considered for each density functional, namely two all‐electron basis sets (a double‐zeta and triple‐zeta formulation) and three basis sets including popular types of effective‐core potentials: Los Alamos, Steven‐Basch‐Krauss, and Stuttgart‐Dresden. The results show that there are presently several better alternatives to the popular B3LYP density functional for the determination of Zn‐ligand bond‐lengths and angles. BB1K, MPWB1K, MPW1K, B97‐2 and TPSS are suggested as the strongest alternatives for this effect presently available in most computational chemistry software packages. In addition, the results show that the use of effective‐core potentials (in particular Stuttgart‐Dresden) has a very limited impact, in terms of accuracy, in the determination of metal‐ligand bond‐lengths and angles in Zinc‐complexes, and is a good and safe alternative to the use of an all‐electron basis set such as 6‐31G(d) or 6‐311G(d,p). © 2009 Wiley Periodicals, Inc. J Comput Chem 2009     

WIDECARS spectra fitting in a premixed ethylene–air flame

WIDECARS measures temperature and mole fractions of most of the major species in ethylene–air flames. One of the issues in implementing this technique is fitting the experimental spectra to theory to obtain flame conditions (temperature, species mole fractions). Individual spectra contain many species resonances, and theory is slow to compute. Libraries of precalculated spectra can be used, but a library of sufficient density for accurate interpolation is large given the many variables. A new fitting algorithm is presented which utilizes a less‐dense library, and additional spectra are calculated during fitting to maintain accuracy. The iterative convergence method converts the problem of minimizing fit error, which converges slowly, to a zero finding problem, which converges reliably, rapidly, and accurately to best fit. Various practical fitting issues, such as the effects of dye laser mode noise and variability, phase‐matching efficiency, and shifts of the spectrum on the spectrometer are addressed. The technique is demonstrated in the analysis of experimental measurements in an equivalence ratio 2.1 ethylene–air flame above the surface of a McKenna burner. Precision errors because of experimental and fitting effects are discussed. Copyright © 2015 John Wiley & Sons, Ltd.     

Lab on Fiber Technology for biological sensing applications

This review presents an overview of “Lab on Fiber” technologies and devices with special focus on the design and development of advanced fiber optic nanoprobes for biological applications. Depending on the specific location where functional materials at micro and nanoscale are integrated, “Lab on Fiber Technology” is classified into three main paradigms: Lab on Tip (where functional materials are integrated onto the optical fiber tip), Lab around Fiber (where functional materials are integrated on the outer surface of optical fibers), and Lab in Fiber (where functional materials are integrated within the holey structure of specialty optical fibers). This work reviews the strategies, the main achievements and related devices developed in the “Lab on Fiber” roadmap, discussing perspectives and challenges that lie ahead, with special focus on biological sensing applications.

     

ChemInform Abstract: Orthorhombic TmGe≈1.9, with a ZrSi2—ErGe1.83 Intergrowth Structure.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.