Search results for "ZINC"

Inhibition of imidazolidinone intermediate formation in the aldol reactions catalyzed by zinc–prolinamide complexes

2011

Abstract The use of zinc salts as cocatalysts in aldol condensations catalyzed by single prolinamide (and in the extension by other more complex prolinamides) can prevent the formation of the parasitic intermediate imidazolidinone, with faster and also more stereoselective reactions than those catalyzed by the free amine. This new finding, together with this ion’s already known properties, make zinc salts highly suitable additives for aldol reactions catalyzed for prolinamide derivatives.

Tristetraprolin Regulates the Expression of the Human Inducible Nitric-Oxide Synthase Gene

2005

The expression of human inducible NO synthase (iNOS) is regulated both by transcriptional and post-transcriptional mechanisms. Stabilization of mRNAs often depends on activation of p38 mitogen-activated protein kinase (p38 MAPK). In human DLD-1 cells, inhibition of p38 MAPK by the compound 4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)1H-imidazole (SB203580) or by overexpression of a dominant-negative p38 MAPKalpha protein resulted in a reduction of human iNOS mRNA and protein expression, whereas human iNOS promoter activity was not affected. An important RNA binding protein regulated by the p38 MAPK pathway and involved in the regulation of the stability of several mRNAs is tr…

In-situ high-pressure x-ray diffraction study of zinc ferrite nanoparticles

2016

We have studied the high-pressure structural behavior of zinc ferrite (ZnFe2O4) nanoparticles by powder X-ray diffraction measurements up to 47 GPa. We found that the cubic spinel structure of ZnFe2O4 remains up to 33 GPa and a phase transition is induced beyond this pressure. The high-pressure phase is indexed to an orthorhombic CaMn2O4-type structure. Upon decompression the low- and high-pressure phases coexist. The compressibility of both structures was also investigated. We have observed that the lattice parameters of the high-pressure phase behave anisotropically upon compression. Further, we predict possible phase transition around 55 GPa. For comparison, we also studied the compressi…

Enantioselective zinc/BINOL-catalysed alkynylation of aldimines generated in situ from α-amido sulfones.

2012

Chiral nonracemic N-Cbz-protected propargylic amines have been prepared by the addition of terminal alkynes to imines generated in situ from α-amido sulfones in the presence of diethylzinc and BINOL-type ligands as catalysts. The reactions give good yields and high enantioselectivities (ee values up to 95 %) for a good number of aromatic and heteroaromatic α-amido sulfones and alkynes.

Electrochemical oxidation of substituted pyrroles.III.Anodic oxidation of 2,5-diphenyl-3-acetylpyrrole

1991

The electrochemical oxidation of 2,5-diphenyl-3-acetylpyrrole (I) is described. The cyclic derivative 1,6a-dihydro-2,5,6a-triphenyl-3,4-diacetylbenzo[g]pyrrolo[3,2-e]indole (II) was obtained in very good yield. However, when water was present in the reaction medium, a different derivative, 4-acetyl-2-hydroxy-2,5-diphenyl-3-(4′-acetyl-2′,5′-diphenyl-3′-yl)-2H-pyrrole (III), was obtained as the main product. 2,2′,5,5′-Tetraphenyl-4,4′-diacetyl-3,3′-dipyrryl (IV), a potentially useful intermediate for the synthesis of condensed pyrroles, was synthesized by zinc reduction of III.

Double stimuli-responsive polysaccharide block copolymers as green macrosurfactants for near-infrared photodynamic therapy

2019

The NIR absorbing photosensitizer phthalocyanine zinc (PC(Zn)) was stabilized in aqueous media as water-dispersible nanoparticles with a reduction- and pH-responsive full polysaccharide block copolymer. A cellular uptake and also photo switchable intracellular activity of the cargo upon irradiation at wavelengths in the near infrared region were shown. The block copolymer was synthesized by applying a copper-free click strategy based on a thiol exchange reaction, creating an amphiphilic double-stimuli-responsive mixed disulfide. The dual-sensitive polysaccharide micelles represent a non-toxic and biodegradable green macrosurfactant for the delivery of phthalocyanine zinc. By encapsulation i…

Front Cover: Facile Synthesis and Self‐Assembly of Zinc (2‐Diethoxyphosphorylethynyl)porphyrins (Eur. J. Inorg. Chem. 10/2019)

2019

The Difficult Marriage of Triarylcorroles with Zinc and Nickel Ions.

2022

The coordination chemistry of corrole has witnessed a great improvement in the past few years and its Periodic Table has been widened to be so large that it is compared with that of porphyrins. However, Ni and Zn ions, commonly used with porphyrins for both synthetic and theoretical purposes, are sparsely reported in the case of corroles. Here, we report synthetic protocols for preparing Ni and Zn triarylcorrole complexes. In the case of Zn, the preliminary oxidation of the free base corrole in DMSO to the neutral corrole radical is a necessary step to obtain the coordination of the metal ion, because the direct reaction led to the formation of an open-chain tetrapyrrole. The Ni complex cou…

On the G‐Quadruplex Binding of a New Class of Nickel(II), Copper(II), and Zinc(II) Salphen‐Like Complexes

2021

αα- and αβ-Zinc-meso-A2B2-tetraarylporphyrins with large optical responses to triethylamine

2012

Synthesis and separation of αα- and αβ-meso-A(2)B(2)-zinc(II) tetraarylporphyrin atropisomers with A = mesityl and B = ortho-phenylethynyl-phenyl are reported. Both isomers exhibit large optical responses upon axial NEt(3) coordination which are visible to the human eye and could therefore be beneficial for the design of smart amine sensing materials. The larger spectral changes as compared to Zn(TPP) are attributed to pronounced distortions of the porphyrin π-system due to steric interactions of the coordinating amine with the porphyrin periphery. This effect as well as the coordination site of NEt(3) at the αα-isomer have been studied by NMR experiments and were rationalized by DFT calcul…