Alkaline metal oxoantimonates(III), A3[SbO3] (A = K or Cs)

The two title trialkaline trioxoantimonates(III), tripotassium trioxoantimonate(III), K₃[SbO₃], (I), and tricaesium trioxo­antimonate(III), Cs₃[SbO₃], (II), crystallize in the cubic Na₃[AsS₃] structure type in space group P2₁3. The structures show discrete Ψ-tetrahedral [SbO₃]³⁻ anions with C_3v point-group symmetry. The Sb—O distances are 1.923 (4) Å in (I) and 1.928 (2) Å in (II), and the O—Sb—O bond angles are 99.5 (2)° in (I) and 100.4 (1)° in (II).     

Synthesis of a mitochondria-targeted spin trap using a novel Parham-type cyclization

A new cyclic nitrone spin trap, [4-(3′,3′-dibutyl-2′-oxy-3′H-isoindol-5′-yloxy)butyl]triphenylphosphonium bromide (MitoSpin), bearing a lipophilic cation has been prepared by a route that involves a novel Parham-type lithiation-cyclization of an isocyanate to give the isoindolinone core. MitoSpin accumulates in a membrane potential dependent way in energized mitochondria and its oxidation could potentially be used in the study of oxidative stress resulting from reactive oxygen species generated in mitochondria.     

Development and validation of a rapid assay based on liquid chromatography–tandem mass spectromtetry for determining macrolide antibiotic residues in eggs

A simple and rapid method able to determine residues of erythromycin A, tylosin and tilmicosin in whole eggs is presented here. The analytical protocol involves a one-step extraction followed by liquid chromatography (LC)–tandem mass spectrometry. Analytes were extracted from 1 g of egg spiked with an internal standard (josamycin) with acetonitrile. In terms of accuracy, matrix effect and ion signal stability, no extract cleanup was found to be necessary. After partial solvent removal, the final extract was injected into the LC column. Extraction was effective, since absolute recovery of the analyte in egg at their maximum residue limit (MRL) level was 85–102%. Estimated limits of quantification (S/N = 10) were 0.2–0.5 ng/g. Based on the EU Commission Decision 2002/657/EC, the method was in-house validated in terms of ruggedness, specificity, linearity, within-laboratory reproducibility, decision limit (CCα) and detection capability (CCβ). The within-laboratory reproducibility, expressed as RSD (n = 18 at the MRL levels), was not higher than 13%. After validation, a short study on EA depletion in eggs was conducted after administration of this drug to laying hens.     

Barium oxoaluminate hydride

The crystal structure of Ba₃(AlO₄)H is isotypic with Ba₃SiS₅ and contains AlO₄^5? and H^? anions. The hydride and oxide anions are coordinated by six Ba and five Ba/one Al atoms in an octahedral geometry. The hydrogen content was ex­amined by MAS–NMR experiments of the deuterated compound.     

Kinetic 12C/13C isotope fractionation by invertase: evidence for a small in vitro isotope effect and comparison of two techniques for the isotopic analysis of carbohydrates

The natural ¹³C/¹²C isotope composition (δ¹³C) of plants and organic compounds within plant organs is a powerful tool to understand carbon allocation patterns and the regulation of photosynthetic or respiratory metabolism. However, many enzymatic fractionations are currently unknown, thus impeding our understanding of carbon trafficking pathways within plant cells. One of them is the ¹²C/¹³C isotope effect associated with invertases (EC 3.2.1.26) that are cornerstone enzymes for Suc metabolism and translocation in plants. Another conundrum of isotopic plant biology is the need to measure accurately the specific δ¹³C of individual carbohydrates. Here, we examined two complementary methods for measuring the δ¹³C value of sucrose, glucose and fructose, that is, off‐line high‐performance liquid chromatography (HPLC) purification followed by elemental analysis and isotope ratio mass spectrometry (EA‐IRMS) analysis, and gas chromatography‐combustion (GC‐C)‐IRMS. We also used these methods to determine the in vitro ¹²C/¹³C isotope effect associated with the yeast invertase. Our results show that, although providing more variable values than HPLC～EA‐IRMS, and being sensitive to derivatization conditions, the GC‐C‐IRMS method gives reliable results. When applied to the invertase reaction, both methods indicate that the ¹²C/¹³C isotope effect is rather small and it is not affected by the use of heavy water (D₂O). Copyright © 2009 John Wiley & Sons, Ltd.     

TMSCl-promoted isocyanide-based MCR of ethylenediamines: an efficient assembling of 2-aminopyrazine core

New trimethylchlorosilane (TMSCl) promoted multicomponent reaction (MCR) of ethylenediamine(s), diverse carbonyl compounds, and isocyanides is proposed for the synthesis of a variety of highly substituted 3,4,5,6-tetrahydropyrazin-2-amines including corresponding spirocyclic compounds.     

Chiral amines in the diastereoselective Mannich-related multicomponent synthesis of diarylmethylamines, 1,2-diarylethylamines, and β-arylethylamines

The multicomponent synthesis of diarylmethylamines, 1,2-diarylethylamines and β-arylethylamines has been undergone starting from aryl- or benzylzinc reagents, aldehydes, and primary or secondary chiral amines. Good to high diastereoselectivities have been obtained from both l-proline ester derivatives 1 and (±)-trans-1-allyl-2,5-dimethylpiperazine (4). The use of R-(+)-1-phenylethylamine (7) provides important diastereoisomeric excesses (∼60%) in conjunction with very high chemical yields. This work constitutes a preliminary entry to the intended development of a more flexible reaction system, involving easily cleavable chiral amines.     

Ytterbium triflate catalyzed synthesis of chlorinated lactones

The direct synthesis of chlorolactones from differently substituted alkenoic acids, using either sodium hypochlorite or chloramine T as the source of electrophilic chlorine and ytterbium triflate hydrate as the Lewis acid is described. In both cases the reactions proceeded in good yields affording selectively five- or six-membered chlorolactones.