Determination of metoserpate,buquinolate, and diclofenac in pork,eggs, and milk using liquid chromatography–tandem mass spectrometry

In this work, a method was developed for the simultaneous determination of residual metoserpate, buquinolate and diclofenac in pork, milk, and eggs. Samples were extracted with 0.1% formic acid in acetonitrile, defatted with n‐hexane, and filtered prior to analysis using liquid chromatography–tandem mass spectrometry. The analytes were separated on a C₁₈ column using 0.1% acetic acid and methanol as the mobile phase. The matrix‐matched calibration curves showed good linearity over a concentration range of 5–50 ng/g with coefficients of determination (R²) ≥0.991. The intra‐ and inter‐day accuracies (expressed as recovery percentage values) calculated using three spiking levels (5, 10, and 20 μg/kg) were 80–108.65 and 74.06–107.15%, respectively, and the precisions (expressed as relative standard deviation) were 2.86–13.67 and 0.05–11.74%, respectively, for the tested drugs determined in various matrices. The limits of quantification (1 and 2 μg/kg) were below the uniform residual level (0.01 mg/kg) set for compounds that have no specific maximum residue limit (MRL). The developed method was tested using market samples and none of the target analytes was detected in any of the samples. The validated method proved to be practicable for detection of the tested analytes in pork, milk, and eggs.     

A masked-alkene metathesis-based synthesis of isopulo’upone

A metathesis-based formal synthesis of (±)-isopulo’upone has been completed featuring a masked olefin metathesis/elimination sequence followed by an intramolecular Diels-Alder reaction to construct the 5,6-fused bicyclic core.     

A total synthesis of 11-O-methyldebenzoyltashironin

A concise total synthesis of 11-O-methyldebenzoyltashironin is reported in which oxidative dearomatization-IMDA-RCM triad constitutes the key ring forming steps, while an unorthodox DIBAL-H mediated stereo- and regioselective reductive epoxide openings and implementation of the vinyl bromide-carbonyl equivalency concept were pivotal to the success of this endeavor.     

Synthesis of 2,6-disubstituted piperidine alkaloids from ladybird beetles Calvia 10-guttata and Calvia 14-guttata

Optically pure (+)-calvine, (+)-2-epicalvine, (2S,6S)-(6-pentylpiperidin-2-yl)acetic acid methyl ester and (2R,6S)-(6-pentylpiperidin-2-yl)acetic acid methyl ester, four piperidine alkaloids isolated from ladybird beetles of the genus Calvia (Coccinellidae), were synthesised from a common precursor using cyclisative Pd(II)/Cu(II)-catalysed carboamination-(methoxy)carbonylation tandem reaction of alkenylamines as a key step. The first single-crystal X-ray analysis of (+)-calvine confirmed its proposed absolute configuration to be (2S,6S) corresponding to that of natural product.     

Photooxidation of glycated and non‐glycated phosphatidylethanolamines monitored by mass spectrometry

Phosphatidylethanolamines (PE) are one of the major components of cells membranes, namely in skin and in retina, that are continuously exposed to solar UV radiation being major targets of photooxidation damage. In addition, due to the presence of the free amine group, PE can also undergo glycation, in hyperglycemic conditions which may increase the susceptibility to oxidation. The aim of this study is to develop a model, based on mass spectrometry (MS) analysis, to identify photooxidative degradation of selected PE (POPE: PE 16:0/18:1, PLPE: PE 16:0/18:2, PAPE: PE 16:0/20:4) and glycated PEs due to UV irradiation. Photooxidation products were analysed by electrospray ionization MS (ESI‐MS) and tandem MS (ESI‐MS/MS) in positive and negative mode. Emphasis is placed in the influence of glycation in the generation of distinct photooxidation products. ESI‐MS spectra of PE after UV photo‐irradiation showed mainly hydroperoxy derivatives, due to oxidation of unsaturated fatty acyl chains. Glycated PE gave rise to several new photooxidation products formed due to oxidative cleavages of the glucose moiety, namely between C1 and C2, C2 and C3, and C5 and C6 of this sugar unit. These new products were identified by ESI‐MS/MS in positive mode showing distinct neutral loss depending on the different structure of the polar head group. These new identified advanced glycated photooxidation products may have a deleterious role in the etiology of diabetic retinopathy and in diabetic retinal microvascular complications. Copyright © 2013 John Wiley & Sons, Ltd.     

微米BCN棒的制备及相关材料的物理性质

轻元素共价键硼碳氮（ＢＣＮ）化合物随组分和原子环境的变化，表现了由半金属到宽湿润地导体之间可调的物理性质，利用偏压辅助的热丝化学气相沉积方法，成功地制备了直径为２０μｍ、长度为１００μｍ的微米量级ＢＣＮ棒，并进一步研究了它的化学成分和原子键态。     

The surface potential of solvent and the intraphase pre-existing potential

Using own and literature data, the differences of real solvation energy for ferricenium and ferrocene in six solvents are found. These quantities are confronted with the calculated difference of the dielectric response energies plus nonelectrostatic energies for the redox couple. Such a comparison allows determining the sum of the surface and intraphase potentials. The comparison of these sums with the experimental values of the surface potential differences obtained by the measuring of Volta potentials allowed determining the differences of pre-existing intraphase potentials formed by solvent molecules on the ferrocene molecule. Thus, the intraphase potentials are evaluated for the first time, using an approach not based on the molecular-dynamic modeling. Using some approximations, the surface potentials of the studied solvents are found.     

An approach to the synthesis of furanoheliangolides through Diels-Alder reactions

The core structure of the natural sesquiterpene lactones furanoheliangolides, an 11-oxabicyclo[6.2.1]undecane system, was synthesized through a pathway involving two Diels-Alder reactions.