Enantioselective catalysis in water: Mukaiyama-aldol condensation promoted by copper complexes of bisoxazolines supported on poly(ethylene glycol)

(S)-3-Phenyl-2-aminopropanol-derived bisoxazolines supported on a modified poly(ethylene glycol) were shown to be effective Cu(II) ligands for the enantioselective Mukaiyama-aldol condensation of various aldehydes with the trimethylsilyl keteneacetal of methyl isobutyrate carried out in water. Enantiomeric excesses comparable to those obtained with nonsupported ligands in the same solvent were observed. The solubility of the ligand in water, ensured by the presence of the polymeric support, allowed a very convenient catalyst-recycling procedure involving simple removal of the reaction product by extraction in Et(2)O and addition of fresh reagents to the catalyst-containing aqueous solution. The chemical and stereochemical efficiency of the catalyst was only marginally eroded over its use in three reaction cycles.     

Trace element determination in seawater by ICP-SFMS coupled with a microflow nebulization/desolvation system

Direct and simultaneous determination of Al, Ag, As, Cd, Co, Cr, Cu, Fe, Mn, Mo, Pb, Sb, U, V and Zn in diluted (1:10 v:v) seawater from the Antarctic Ocean and the Venice Lagoon at the ng mL^–1 and pg mL^–1 level has been performed by using an inductively coupled plasma sector field mass spectrometer (ICP-SFMS). Samples were analysed by using a PFA microflow nebulizer coupled with a desolvation system or a PFA microflow nebulizer coupled with a Teflon spray chamber, respectively. Measurements were carried out at low (LR, m/m=300), medium (MR, m/m=3,000) and high (HR, m/m=7,500) resolutions depending on the studied isotope. To avoid contamination, sample pre-treatment was carried out in a clean laboratory equipped with a Class 100 vertical laminar flow hood. Concentration ranges (minimum–maximum in ng mL^–1) found in the Antarctic seawater samples (in depth profiles) were: Ag 0.0004–0.0018, As 0.69–1.32, Cd 0.031–0.096, Co 0.018–0.065, Cr 0.18–0.46, Cu 0.04–1.58, Fe 0.13–1.63, Mn 0.02–0.12, Mo 5.97–12.46, Pb 0.007–0.074, Sb 0.033–0.088, U 0.5–1.9, V 0.6–2.5 and Zn 0.16–0.80. Concentration ranges (min–max in ng mL^–1) found in the Venice Lagoon water samples (temporal profile from a benthic chamber experiment) were: Al 0.24–0.61, Ag 0.007–0.031, As 1.42–2.27, Cd 0.050–0.182, Co 0.440–1.461, Cr 0.15–0.34, Cu 0.81–2.46, Fe 0.25–1.66, Mn 11.6–31.7, Mo 6.50–10.6, Pb 0.047–0.225, Sb 0.240–0.492, U 1.7–3.3, V 1.3–2.8 and Zn 5.20–21.5. The detection limits range between 0.06 pg mL^–1 for Ag and U to 15 pg mL^–1 for Fe. In order to check the accuracy of the analytical procedure, measurements of the trace elements in a certified reference material (coastal Atlantic seawater, CASS-4-NRCC) were compared with the certified values. In addition, the results from the Antarctic and Venice Lagoon samples were compared with those obtained by using different analytical techniques.     

Through-space interactions between face-to-face,center-to-edge oriented arenes: importance of polar-pi effects

Two series of conformationally restricted polycyclic compounds (1-3 and 4-7) have been synthesized as model systems for studying the through-space interactions between face-to-face, center-to-edge (parallel-offset) oriented arenes. These compounds feature different X substituents on one of the interacting rings. By monitoring the variation of the delta Gz for the rotation around the aryl-aryl bond in 1-7 as a function of X by 2D [1H,1H] EXSY NMR spectroscopy, it was found that the barriers increase on passing from electron-donating to electron-withdrawing substituted derivatives. Quantum mechanical calculations [MP2/DVZ (2d,p)//B3LYP/DVZ(2d,p)] gave barrier values and variations in agreement with the experimental data. The results are consistent with a repulsive arene-arene interaction dominated by electrostatic effects.     

InBr3-catalyzed Friedel-Crafts addition of indoles to chiral aromatic epoxides: a facile route to enantiopure indolyl derivatives

Aromatic optically active epoxides can be opened in a regioselective and clean way with indoles in the presence of catalytic amount of InBr3 (1 mol %). The reaction takes place with a SN2 pathway affording the 2-aryl-2-(3'-indolyl)ethan-1-ols with excellent enantioselectivity (ee up to 99%).     

Efficient synthesis of an enantiopure beta-lactam as an advanced precursor of thrombin and tryptase inhibitors

A new and efficient synthesis of a beta-lactam that is an advanced precursor of inhibitors of thrombin and tryptase is reported. The reaction sequence is based on the use of an inexpensive enantiomerically pure starting material and is designed to allow access to both enantiomers of the target molecules by epimerization of a side-product obtained along the synthesis. An improved procedure for the epimerization step that takes advantage of the use of a polymer-supported and recyclable phase-transfer catalyst is described.     

Die Oxydoreduktionsreaktionen des Germaniums an der Quecksilbertropfelektrode

Zusammenfassung Die Reduktionsvorgänge bzw. Oxydationsvorgänge des zweiwertigen Germaniums zum Metall bzw. zur Germaniumsäure imph-Bereich 0 bis 6 wurden untersucht. Es handelt sich in allen Fällen um nicht reversible Prozesse, teils weil das Germanium kein Amalgam bildet, teils wegen des gleichzeitigen Vorhandenseins vieler verschiedener Ionenformen. Reduktion und Oxydation werden beiph > 1 von der Acidität in gewohnter Weise beeinflußt, weil — wie wir annehmen — das Germanium-II-Ion unter diesen Umständen als basisches Ion vorliegt. Beiph <0,5 ist die Acidität ohne Einfluß auf das Halbwellenpotential des Reduktionsvorganges. Darin ist eine Bestätigung für die Anwesenheit von in stark saurer Lösung beständigen GeCl ₃ ^- -Ionen zu erblicken.

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Summary A study was made of the redox reactions of bivalent germanium leading to the metal or to germanic acid in theph range 0–6. All cases dealt with irreversible reactions, partly because germanium does not form an amalgam, and partly because of the simultaneous presence of many different ionic forms. Atph > 1, the reduction and oxidation are affected in the usual way by the acidity, because — as we assume — the germanium(II) ion is present under these conditions as a basic ion. Atph < 0.5, the acidity is without influence on the half wave potential of the reduction process. This may be viewed as a confirmation of the presence of the stable GeCl ₃ ^- ions in strong acid solution.

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Résumé On a expérimenté les processus de réduction et d'oxydation du germanium bivalent en métal ou en acide germanique dans le domaine deph de 0 à 6. Il ne s'agit pas de processus réversibles dans tous les cas parce que le germanium ne donne pas d'amalgame et à cause de la présence simultanée de différentes formes ioniques variées. La réduction et l'oxydation sont influencées pourph > 1, comme d'usage, par l'acidité car, comme nous le supposons, dans ces conditions, l'ion Germanium bivalent se trouve à l'état d'ion basique. Pourph < 0,5, l'acidité est sans influence sur le potentiel de demi-palier et sur le processus de réduction. Il faut supposer en solution fortement acide la présence d'ion GeCl ₃ ^- instable.

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Mit 3 Abbildungen.     

Imidazolyl derivatives of the chroman ring. 1

The synthesis of 2-(1H-imidazol-1-yl)-2,3-dihydro-2H-1-benzopyran-4-ones (I) through 3-bromo-2,3-dihydro-4H-1-benzopyran-4-ones or more conveniently through chroman ring closure from 2-(1H-imidazol-1-yl)-2′-hydroxyacetophenones is described. The ring closure also works well for the pyrazolyl derivatives. Compounds I and the corresponding imidazolylchromanols, -chromenes, and -chromans derived from the former, were pharmacologically investigated.     

Toxic elements content in PM<Subscript>10</Subscript> samples from a coastal area of the Northern Adriatic Sea

PM₁₀ samples were collected during winter and summer seasons at two different sites in the area of Trieste (Italy). The content of As, Cd, Cr, Mn, Ni, Pb and V in the PM₁₀ samples was determined by inductively coupled plasma-mass spectrometry, with the purpose of evaluating the relevance of PM₁₀ inhalation as a route of human exposure to these elements. The results showed that the ambient air concentration of the aforementioned elements were below the limits or target values for both sites and season. Site and season-specific correlation analysis was conducted for the identification of metals with similar origin: very good correlation for the couple Ni-V was found in both sites and seasons, showing the influence of combustion of heavy oils in PM₁₀ composition. The inter-site and seasonal variability of both PM₁₀ and metal concentrations were examined. A stronger impact by the vehicular traffic on the PM₁₀ and metal concentrations was found for the urban site in both seasons. Because of the great importance of the “Bora” wind on the local climate, variability of PM₁₀ and toxic elements concentration with wind were analysed, allowing determination of the effect of wind on dilution of the pollutants for the urban site during both seasons.      

A hyphenated microLC-Q-TOF-MS platform for exosomal lipidomics investigations: application to RCC urinary exosomes

Urinary exosomes are released from every renal epithelial cell type facing the urinary space and therefore, they may carry molecular markers of renal dysfunction and structural injury. Here, we present a hyphenated microLC-Q-TOF-MS platform for lipidomics studies applied to investigate the urinary exosome lipid repertoire. Lipids were separated by reversed-phase chromatography using a linear gradient of formic acid 0.2% and tetrahydrofuran, in 40 min of analysis. Features (m/z with associated own retention time) were extracted by MarkerLynx(TM) (Waters) and processed, demonstrating good analytical performance in terms of repeatability and mass accuracy of the microLC Q-TOF MS platform. In particular, a stable retention time (RSD less than 4%) and relative intensity (RSD from 2.9% to 11%) were observed. Moreover, the method takes advantages by the use of a lock spray interface (Waters) that allows readjusting the m/z data after acquisition, obtaining inaccuracy below 6 ppm in measuring the m/z value of the reference compound during chromatographic run. The method was employed in a preliminary application to perform comparative analysis from healthy control subjects and renal cell carcinoma (RCC) patients, in order to possibly highlight differences in lipid composition to be exploited as potential tumor biomarker. Differential lipid composition in RCC urinary exosomes was achieved and tentatively identified by accurate mass, providing a preliminary indication of a relationship between lipid composition of urinary exosomes and RCC disease. Among the total features significantly different in RCC exosomes, the ion at m/z 502.3 was taken as an example for molecular confirmation by MS/MS fragmentation analysis.