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111.
112.
Sergio Auricchio Ada M. Truscello Mirvana Lauria Stefano V. Meille 《Tetrahedron》2012,68(36):7441-7449
2H-Azirines were found to react with imines, enaminones and enaminoesters in the presence of metal salts. Imidazoles, pyrroles and new pyrrolinones derivatives are isolated in good overall yields. The role of metal salts was investigated as they can act as Lewis acids or electron donors. Mechanisms are proposed suggesting that imidazoles arise from addition of azirine to imines via radical or ionic mechanism; pyrroles and pyrrolinones are obtained from azirines with enamino derivatives when the salt acts as a Lewis acid. In the latter case the properties of the metallic compound influence the reaction regioselectivity. 相似文献
113.
114.
Miguel A. Harvey María E. Díaz de Vivar Ricardo Baggio Sergio Baggio 《Journal of chemical crystallography》2011,41(11):1717-1721
Abstract
The title compound is monomeric with a Zn(II) hexacoordinated center. The coordination sphere is formed by four nitrogens from two phenanthroline molecules, one oxygen from a monodentate peroxodisulfate ion, and one oxygen from a water molecule. A non-coordinated water molecule completes the formula with an important role in the stabilization of the structure through the formation of two OHW–H···Opds bridges (acting as a donor) and one OCW–H···OHW bridge where it is an acceptor group (HW: hydration water; pds: peroxodisulfato; CW: coordinated water). The compound is triclinic, space group P-1 with a = 8.763 (3) ?, b = 9.068 (3) ?, c = 17.531 (6) ?, α = 96.48 (2)°, β = 103.94 (3)°, γ = 104.57 (3)°, V = 1286.0 (7) ?3 and Z = 2. The structure was solved by direct methods with a conventional R (on F) = 0.050 for 4534 reflections with Fo > 4σ(Fo). The compound is isomorphous with the Cd analogue (in Harvey et al. Aust J Chem 54:307, 2001). An eventual dependence of conformation and coordination mode of the peroxodisulfate anion on the ancillary organic ligand taking part in the coordination compounds analyzed is discussed. 相似文献115.
116.
117.
Paola Peluso Victor Mamane Emmanuel Aubert Sergio Cossu 《Journal of separation science》2013,36(18):2993-3003
The HPLC enantioseparation of nine atropisomeric 3,3′,5,5′‐tetrasubstituted‐4,4′‐bipyridines was performed in normal and polar organic (PO) phase modes using two immobilized polysaccharide‐based chiral columns, namely, Chiralpak IA and Chiralpak IC. The separation of all racemic analytes, the effect of the chiral selector, and mobile phase (MP) composition on enantioseparation and the enantiomer elution order (EEO) were studied. The beneficial effect of nonstandard solvents, such as tetrahydrofuran (THF), dichloromethane (DCM), and methyl t‐butyl ether on enantioseparation was investigated. All selected 4,4′‐bipyridines were successfully enantioseparated on Chiralpak IA under normal or PO MPs with separation factors from 1.14 to 1.70 and resolutions from 1.3 to 6.5. Two bipyridines were enantioseparated at the multimilligram level on Chiralpak IA. Differently, Chiralpak IC was less versatile toward the considered class of compounds and only five bipyridines out of nine could be efficiently separated. In particular, on these columns, the ternary mixture n‐heptane/THF/DCM (90:5:5) as MP had a positive effect on enantioseparation. An interesting phenomenon of reversal of the EEO depending on the composition of the MP for the 3,3′‐dibromo‐5,5′‐bis‐(E)‐phenylethenyl‐4,4′‐bipyridine along with an exceptional enantioseparation for the 3,3′‐dibromo‐5,5′‐bis‐ferrocenylethynyl‐4,4′‐bipyridine (α = 8.33, Rs = 30.6) were observed on Chiralpak IC. 相似文献
118.
A sample extraction and purification procedure that uses ammonium-salt-induced acetonitrile/water phase separation was developed and demonstrated to be compatible with the recently reported method for pesticide residue analysis based on fast extraction and dilution flow injection mass spectrometry (FED-FI-MS). The ammonium salts evaluated were chloride, acetate, formate, carbonate, and sulfate. A mixture of NaCl and MgSO4, salts used in the well-known QuEChERS method, was also tested for comparison. With thermal decomposition/evaporation temperature of <350 °C, ammonium salts resulted in negligible ion source residual under typical electrospray conditions, leading to consistent method performance and less instrument cleaning. Although all ammonium salts tested induced acetonitrile/water phase separation, NH4Cl yielded the best performance, thus it was the preferred salting out agent. The NH4Cl salting out method was successfully coupled with FI/MS/MS and tested for fourteen pesticide active ingredients: chlorantraniliprole, cyantraniliprole, chlorimuron ethyl, oxamyl, methomyl, sulfometuron methyl, chlorsulfuron, triflusulfuron methyl, azimsulfuron, flupyrsulfuron methyl, aminocyclopyrachlor, aminocyclopyrachlor methyl, diuron and hexazinone. A validation study was conducted with nine complex matrices: sorghum, rice, grapefruit, canola, milk, eggs, beef, urine and blood plasma. The method is applicable to all analytes, except aminocyclopyrachlor. The method was deemed appropriate for quantitative analysis in 114 out of 126 analyte/matrix cases tested (applicability rate = 0.90). The NH4Cl salting out extraction/cleanup allowed expansion of FI/MS/MS for analysis in food of plant and animal origin, and body fluids with increased ruggedness and sensitivity, while maintaining high-throughput (run time = 30 s/sample). Limits of quantitation (LOQs) of 0.01 mg kg−1 (ppm), the ‘well-accepted standard’ in pesticide residue analysis, were achieved in >80% of cases tested; while limits of detection (LODs) were typically in the range of 0.001–0.01 mg kg−1 (ppm). A comparison to a well-established HPLC/MS/MS method was also conducted, yielding comparable results, thus confirming the suitability of NH4Cl salting out FI/MS/MS for pesticide residue analysis. 相似文献
119.
Patrizia Scafato Francesca Caprioli Laura Pisani Daniele Padula Fabrizio Santoro Giuseppe Mazzeo Sergio Abbate France Lebon Giovanna Longhi 《Tetrahedron》2013
Three forms of chiroptical spectroscopies, electronic circular dichroism (ECD), vibrational circular dichroism (VCD), and optical rotatory dispersion (ORD) have been employed to study the configuration and conformational properties of the three molecules: (S)-3-phenylcyclopentanone, (S)-3-phenylcyclohexanone, and (S)-3-phenylcycloheptanone (including (S)-3-phenylcyclopentanone-2,2,5,5-d4 and (S)-3-phenylcyclohexanone-2,2,6,6-d4). ECD and VCD spectra in the mid-IR for the three molecular systems are marginally dependent on fine conformational details, as interpreted in terms of standard DFT computational methods, with common spectroscopic features to the three systems clearly identified. Accounting for vibronic coupling mechanisms reproduces the structuring of ECD n→π∗ band. The ORD curves are quite similar for the three types of molecules, but their interpretation highlights a crucial role played by conformations of the cycloalkanone ring in the case of (S)-3-phenylcycloheptanone. The same conclusions are reached by considering the VCD spectra in the CH-stretching region. 相似文献
120.
Sergio Català‐Clariana Fernando Benavente Estela Giménez José Barbosa Victoria Sanz‐Nebot 《Electrophoresis》2013,34(13):1886-1894
Biologically active peptides derived from complex bovine milk protein hydrolysates are of particular interest in food science and nutrition because they have been shown to play different physiological roles, providing benefits in human health. In this study, we used CE‐TOF‐MS for separation and identification of bioactive peptides in three hypoallergenic infant milk formulas. An appropriate sample cleanup using a citrate buffer with DTT and urea followed by SPE with Sep‐Pack® C18 and StrataXTM cartridges allowed the detection of a large number of low molecular mass bioactive peptides. This preliminary identification was solely based on the measured experimental monoisotopic molecular mass values (Mexp). Later, we evaluated the classical semiempirical relationships between electrophoretic mobility and charge‐to‐mass ratio (me vs. q/Mα, α = 1/2 for the classical polymer model) to describe their migration behavior. The assistance of migration prediction proved to be useful to improve reliability of the identification, avoiding misinterpretations and solving some identity conflicts. After revision, the identity of 24, 30, and 38 bioactive peptides was confirmed in each of the three infant milk formulas. A significant number of these peptides were reported as inhibitors of angiotensin‐converting enzyme, however, the presence of sequences with other biological activities such as antihypertensive, antithrombotic, hypocholesterolemic, immunomodulation, cytotoxicity, antioxidant, antimicrobial, antigenic, or opioid was also confirmed. 相似文献