Conformational analysis of N-isopropylbenzohydroxamic acids: crystal structure, DFT, and NMR studies

X-ray crystal structure determinations together with density functional theory (DFT) calculations in vacuo and NMR studies in solution have been carried out for 4-MeOC₆H₄CONPrⁱOH 2a and 3,5-(NO₂)₂C₆H₃CONPrⁱOH 2b. The results were compared with that for the respective N-methyl benzohydroxamic acids. For crystal structures as well as for DFT-optimized geometries of 2 (both isomers) in vacuo, the effect of substituents in aromatic ring manifested by changing of charges is inconspicuous. Studies of potential energy surfaces showed that libration barrier around ω ₁ = 0° is low enough to make electron conjugation feasible, and that for 2b rotation barrier around C(O)N bond is higher by 6 kcal/mol and additionally, that rotation around N–C bond is hindered. A careful analysis of low-temperature ¹H NMR spectra confirmed the greater stability of Z-2a, the greater rigidity of E-2b and the influence of solvent on both isomers population. Despite solvent-dependent conformational alteration, both 2a and 2b crystallize exclusively as E isomers from ethyl acetate solution. Correlations of absolute ¹H, ¹³C, and ¹⁵N shielding calculations with experimental data were also analyzed. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

(2,2′‐Bipyridine)bis(tri‐tert‐butoxysilanethiolato‐κS)lead(II) and (4,7‐diphenyl‐1,10‐phenanthroline‐κ2N,N′)bis(tri‐tert‐butoxysilanethiolato‐κS)lead(II) benzene hemisolvate

In the title mononuclear lead silanethiolates, [Pb(C₁₂H₂₇O₃SSi)₂(C₁₀H₈N₂)], (I), and [Pb(C₁₂H₂₇O₃SSi)₂(C₂₄H₁₆N₂)]·0.5C₆H₆, (II), the Pb atom shows a distorted square‐pyramidal coordination with a PbON₂S₂ core in which one S atom lies in an axial position. Intermolecular π–π and C—H...π interactions stabilize the structures. The benzene solvent molecule in (II) lies on an inversion centre.     

Convergent beam camera for structure analysis of microcrystals

An X-ray tube with external miniature anode was constructed and mounted inside of a cylindrical diffraction camera in the immediate vicinity of the crystal holder. The distance of specimen from tube focus is 15 mm. This special construction allows to obtain diffractograms of small crystal specimens (∼ 10⁻³ mm in diameter) at reasonable exposure time (several hours).     

Immunomodulatory Properties of Polysaccharide-Rich Young Green Barley (Hordeum vulgare) Extract and Its Structural Characterization

Young green barley (YGB) water extract has revealed a beneficial impact on natural killer (NK) cells’ ability to recognize and eliminate human colon cancer cells, without any side effects for normal colon epithelial cells. The direct anticancer effect of the tested compounds has been also shown. The mixture of oligosaccharides found in this extract was characterized by chemical analyses and via FT-IR spectroscopy and MALDI-TOF MS techniques. The YGB preparation contained 26.9% of proteins and 64.2% of sugars, mostly glucose (54.7%) and fructose (42.7%), with a small amount of mannose (2.6%) and galactose (less than 0.5%). Mass spectrometry analysis of YGB has shown that fructose oligomers contained from 3 to 19 sugar units. The number of fructans was estimated to be about 10.2% of the dry weight basis of YGB. The presented results suggest the beneficial effect of the consumption of preparations based on young barley on the human body, in the field of colon cancer prevention.     

Ueber die Bestimmung der Phosphors?ure in Phosphoriten

Ohne Zusammenfassung     

N-Phenacyldibromobenzimidazoles—Synthesis Optimization and Evaluation of Their Cytotoxic Activity

Antifungal N-phenacyl derivatives of 4,6- and 5,6-dibromobenzimidazoles are interesting substrates in the synthesis of new antimycotics. Unfortunately, their application is limited by the low synthesis yields and time-consuming separation procedure. In this paper, we present the optimization of the synthesis conditions and purification methods of N-phenacyldibromobenzimidazoles. The reactions were carried out in various base solvent-systems including K₂CO₃, NaH, KOH, t-BuOK, MeONa, NaHCO₃, Et₃N, Cs₂CO₃, DBU, DIPEA, or DABCO as a base, and MeCN, DMF, THF, DMSO, or dioxane as a solvent. The progress of the reaction was monitored using HPLC analysis. The best results were reached when the reactions were carried out in an NaHCO₃–MeCN system at reflux for 24 h. Additionally, the cytotoxic activity of the synthesized compounds against MCF-7 (breast adenocarcinoma), A-549 (lung adenocarcinoma), CCRF-CEM (acute lymphoblastic leukemia), and MRC-5 (normal lung fibroblasts) was evaluated. We observed that the studied cell lines differed in sensitivity to the tested compounds with MCF-7 cells being the most sensitive, while A-549 cells were the least sensitive. Moreover, the cytotoxicity of the tested derivatives towards CCRF-CEM cells increased with the number of chlorine or fluorine substituents. Furthermore, some of the active compounds, i.e., 2-(5,6-dibromo-1H-benzimidazol-1-yl)-1-(3,4-dichlorophenyl)ethanone (4f), 2-(4,6-dibromo-1H-benzimidazol-1-yl)-1-(2,4,6-trichlorophenyl)ethanone (5g), and 2-(4,6-dibromo-1H-benzimidazol-1-yl)-1-(2,4,6-trifluorophenyl)ethanone (5j) demonstrated pro-apoptotic properties against leukemic cells with derivative 5g being the most effective.     

Die Indizierung der Silbertitration mit Hilfe der Glaselektrode

Zusammenfassung Die Elektrodenfunktionen eines Glases, bestehend aus (Mol-%) 27% Na₂O, 8% Al₂O₃ und 65% SiO₂, wurden gegenüber verschiedenen Kationen geprüft. Die Glaselektrode zeigt eine ausgeprägte Silberfunktion und läßt sich als Indicatorelektrode bei der Fällungstitration des Silberions mit Halogenid im neutralen Medium einsetzen. Als günstigster Titrator erwies sich Magnesiumchlorid, das zu einem deutlichen Potentialsprung im Äquivalenzpunkt führt. Zweiwertige Kationen beeinflussen die Indizierung nicht, wohl aber stören größere Mengen an Alkaliionen.

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Summary The electrode functions of a glass, containing (mol-%) 27% Na₂O, 8% Al₂O₃, and 65% SiO₂, have been tested against different cations. Such a glass electrode exhibits a distinct silver function and can be applied as indicator electrode to the precipitation titration of silver ion with halogenide in neutral medium. Magnesium chloride proved to be the most favourable titrator, yielding clear jumps in potential at the equivalence point. The indication is not influenced by divalent cations, larger amounts of alkali ions, however, interfere.

     

(Cyclopentadienyl){(N,N-dimethylaminoethyl)cyclopentadienyl} complexes of zirconium: Crystal structure of [(η-C5H5)(η-C5H4CH2CH2NHMe2)ZrCl2]2[ZrCl6]

[(η⁵-C₅H₅)ZrCl₃] reacts with [C₅H₄CH₂CH₂NMe₂]Li yielding the coordination polymer [(C₅H₅)(C₅H₄CH₂CH₂NMe₂)ZrCl₂]_n (1) as a brown solid which is very sensitive to moisture. The reaction of 1 with 1.35 equivalent of HCl (methanolic solution) yields pale yellow green crystals of [(η⁵-C₅H₅)(η⁵-C₅H₄CH₂CH₂NHMe₂)ZrCl₂]₂[ZrCl₆] (2). Compound 2 was fully characterized on the basis of NMR data and X-ray crystal structure analysis. The formation of this product indicates the elimination of C₅H₄CH₂CH₂NMe₂ as well as C₅H₅ ligands from the Zr(IV) metal centre.     

Resemblance analysis of molecular systems on the grounds of DFT-evaluated parameters. Platinum complexes and their anticancer activity

The molecular properties characterizing diammine platinum complexes have by way of example been analyzed and selected because of their role in anticancer activity. The research was done with the use of the nonstandard quantitative method to compare molecular properties resulting from density functional theory (DFT). Among different molecular parameters considered, the multipole moment components were found mainly to have clear correspondence to the trans (anticancer neutral) and cis classes of platinum complexes. The results led to the selection and conjecture of the specific significance of some molecular characteristics contrasted with other assemblies of parameters. © 1996 John Wiley & Sons, Inc.