Synthesis and Prediction of the Ubiquinol‐cytochrome c Reductase Inhibitory Activity of 3,4‐Dihydroisoquinolines and 2‐Azaspiro[4.5]decanes (Spiropyrrolines)

Isoquinolines rank as the second largest group among the plant alkaloids. Natural isoquinolines and synthetic isoquinoline derivatives exhibit numerous biological activities. In this study, the approaches to synthesis of new 3,4‐dihydroisoquinoline and 2‐azaspiro[4.5]decane (spiropyrroline) derivatives annelated by C(3)─C(4) bonds with a cyclohexyl or cyclopentyl moiety have been developed. In accord with the results of biological activity prediction by the pass software, molecular docking was carried out on the ubiquinol‐cytochrome c reductase (bc₁ complex) model. Compounds 6e and 12a , d were found out as potential Q₀ site inhibitors of the bovine bc₁ complex.     

Synthesis of Anti-Inflammatory Spirostene-Pyrazole Conjugates by a Consecutive Multicomponent Reaction of Diosgenin with Oxalyl Chloride,Arylalkynes and Hydrazines or Hydrazones

Steroid sapogenin diosgenin is of significant interest due to its biological activity and synthetic application. A consecutive one-pot reaction of diosgenin, oxalyl chloride, arylacetylenes, and phenylhydrazine give rise to steroidal 1,3,5-trisubstituted pyrazoles (isolated yield 46–60%) when the Stephens–Castro reaction and heterocyclization steps were carried out by heating in benzene. When the cyclization step of alkyndione with phenylhydrazine was performed in 2-methoxyethanol at room temperature, steroidal α,β-alkynyl (E)- and (Z)-hydrazones were isolated along with 1,3,5-trisubstituted pyrazole and the isomeric 2,3,5-trisubstituted pyrazole. The consecutive reaction of diosgenin, oxalyl chloride, phenylacetylene and benzoic acid hydrazides efficiently forms steroidal 1-benzoyl-5-hydroxy-3-phenylpyrazolines. The structure of new compounds was unambiguously corroborated by comprehensive NMR spectroscopy, mass-spectrometry, and X-ray structure analyses. Performing the heterocyclization step of ynedione with hydrazine monohydrate in 2-methoxyethanol allowed the synthesis of 5-phenyl substituted steroidal pyrazole, which was found to exhibit high anti-inflammatory activity, comparable to that of diclofenac sodium, a commercial pain reliever. It was shown by molecular docking that the new derivatives are incorporated into the binding site of the protein Keap1 Kelch-domain by their alkynylhydrazone or pyrazole substituent with the formation of more non-covalent bonds and have higher affinity than the initial spirostene core.     

History-dependent ion transport through conical nanopipettes and the implications in energy conversion dynamics at nanoscale interfaces

The dynamics of ion transport at nanostructured substrate–solution interfaces play vital roles in high-density energy conversion, stochastic chemical sensing and biosensing, membrane separation, nanofluidics and fundamental nanoelectrochemistry. Further advancements in these applications require a fundamental understanding of ion transport at nanoscale interfaces. The understanding of the dynamic or transient transport, and the key physical process involved, is limited, which contrasts sharply with widely studied steady-state ion transport features at atomic and nanometer scale interfaces. Here we report striking time-dependent ion transport characteristics at nanoscale interfaces in current–potential (I–V) measurements and theoretical analyses. First, a unique non-zero I–V cross-point and pinched I–V curves are established as signatures to characterize the dynamics of ion transport through individual conical nanopipettes. Second, ion transport against a concentration gradient is regulated by applied and surface electrical fields. The concept of ion pumping or separation is demonstrated via the selective ion transport against concentration gradients through individual nanopipettes. Third, this dynamic ion transport process under a predefined salinity gradient is discussed in the context of nanoscale energy conversion in supercapacitor type charging–discharging, as well as chemical and electrical energy conversion. The analysis of the emerging current–potential features establishes the urgently needed physical foundation for energy conversion employing ordered nanostructures. The elucidated mechanism and established methodology can be generalized into broadly-defined nanoporous materials and devices for improved energy, separation and sensing applications.     

One-pot,three-component synthesis of spiro[indeno[1,2-b]quinoline-10,3′-pyrroles] via the Hantzsch-type reaction of 1H-pyrrole-2,3-diones

A new methodology for the synthesis of spiro[indeno[1,2-b]quinoline-10,3′-pyrrole] derivatives via a Hantzsch-type reaction has been developed. This process involves the one-pot, three-component reaction of a 1H-pyrrole-2,3-dione, an aminocyclohexenone and 1,3-indanedione in acetic acid at reflux. Operationally simple, metal-free reaction conditions, simplicity of product isolation and good yields are key advantages of this methodology.     

Metamaterial polarization converter analysis: limits of performance

In this paper, we analyze the theoretical limits of a metamaterial-based converter with orthogonal linear eigenpolarizations that allow linear-to-elliptical polarization transformation with any desired ellipticity and ellipse orientation. We employ the transmission line approach providing a needed level of the design generalization. Our analysis reveals that the maximal conversion efficiency for transmission through a single metamaterial layer is 50 %, while the realistic reflection configuration can give the conversion efficiency up to 90 %. We show that a double layer transmission converter and a single layer with a ground plane can have 100 % polarization conversion efficiency. We tested our conclusions numerically reaching the designated limits of efficiency using a simple metamaterial design. Our general analysis provides useful guidelines for the metamaterial polarization converter design for virtually any frequency range of the electromagnetic waves.     

Vibrational Coupling between Organic and Inorganic Sublattices of Hybrid Perovskites

The interplay of electronic and nuclear degrees of freedom in semiconductor hybrid organic–inorganic perovskites determines many of their fundamental photophysical properties. For instance, charge carriers are dressed with phonons, that is, form polarons, and combination modes composed of strongly mixed localized vibrations and delocalized phonons can provide pathways for electronic energy relaxation and dissipation. Mixing of the different types of nuclear motion in vibrational combination modes requires their strong coupling. The direct measurement of coupling between the high‐frequency N?H stretch modes of the organic methylammonium and formamidinium ions and low‐frequency Pb?I phonon modes of the inorganic sub‐lattice in hybrid organic–inorganic perovskites is presented. The results reveal direct and substantial coupling between the non‐covalently interacting organic and inorganic sub‐lattices.