Solid-phase microextraction gas chromatography/mass spectrometry: a new method for species identification of truffles

This study describes a rapid method to identify different truffle species by analysis of their volatile compound fraction using static headspace solid-phase microextraction gas chromatography/mass spectrometry. The volatile organic compounds (VOCs) were extracted using a new 2-cm 50/30 microm DVB/CAR/PDMS fiber placed for 10 min in the headspace of the truffle sample with the vial maintained at 20 degrees C (in a thermostatically controlled analysis room). The mass spectra of the VOC chromatograms were represented as 'fingerprints' of the analysed samples. Next, stepwise factorial discriminant analysis afforded a limited number of characteristic fragment ions that allowed a classification of the truffle species studied. This new method provides an effective approach to rapid quality control and identification of truffle species by analysis of their volatile fraction. Moreover, this method offers the advantage of minimizing thermal, mechanical, and chemical modifications of the truffles, thereby reducing the risk of analytical artifacts.     

N-Haloamidines-V: Reaction of N-chloro-N'-aroyl-acetamidines and -benzamidines with enamines

The reaction between N-chloro-N'-aroyl-amidines and β,β-disubstituted enamines affords 1 - aroyl - 4 -amino - 4,5 - dihydro - imidazoles in low yields, the main reaction product being N - (2 - morpholino - 2,2 -disubstituted) - ethylidene - N' - aroyl - amidines. A similar reaction course was not observed with enamines bearing a hydrogen atom in the β-position. In this case only products derived from electrophilic chlorination on enamines were isolated.     

Baeyer-Villiger oxidation with potassium peroxomonosulfate supported on acidic silica gel

[reaction: see text] Potassium peroxomonosulfate deposited onto silica SiO2 x KHSO5 efficiently reacts with ketones in dichloromethane at room temperature to give the corresponding esters or lactones in quantitative yields. This method avoids hydrolysis of the reaction products. The Baeyer-Villiger reaction is catalyzed by potassium hydrogensulfate present in the supported reagent.     

Resonance assignments and secondary structure analysis of E. coli thioredoxin by magic angle spinning solid-state NMR spectroscopy

De novo site-specific 13C and 15N backbone and sidechain resonance assignments are presented for uniformly enriched E. coli thioredoxin, established using two-dimensional homo- and heteronuclear solid-state magic angle spinning NMR correlation spectroscopy. Backbone dihedral angles and secondary structure were derived from the statistical analysis of the secondary chemical shifts, and are in good agreement with solution values for the intact full-length thioredoxin, with the exception of a small number of residues located at the termini of the individual secondary structure elements. A large number of cross-peaks observed in the DARR spectra with long mixing times correspond to the pairs of carbon atoms separated by 4-6 angstroms, suggesting that DARR could be efficiently employed for observation of medium- and long-range correlations. The 108 amino acid residue E. coli thioredoxin is the largest uniformly enriched protein assigned to this degree of completeness by solid-state NMR spectroscopy to date. It is anticipated that with a combination of two-dimensional correlation experiments and high magnetic fields, resonance assignments and secondary structure can be generally derived for other noncrystalline proteins.     

离子性指数、极化效应指数烷烃^13C NMR化学位移的 关系研究

定义了烷烃分子中碳原子的离子性指数(INI)，用离子性指数(INI)、极化效应指数(PEI)及N^i~H(i=αβΥ)结构信息参数研究了烷烃的^13CNMR化学位移模型，结果表明，烷烃^13CNMR化学位移(CS)可用下式来定量描述：CS=194.6156-37.7394(INI)+98.6505(ΣPEI)+27.1630(INI/ΣPEI)-652.9106(ΣPEI/INI)+0.7735N^α~H+2.2468N^β~H-0.1742N^γ~H。用上式估算了304个碳原子的化学位移，平均绝对误差仅为0.77δ，标准差0.9860δ，预测值与实验值非常吻合。     

Highly stereoselective synthesis, structure, and application of (E)-9-[2-(silyl)ethenyl]-9H-carbazoles

(E)-N-(Silyl)vinylcarbazole has been easily prepared via a new catalytic route, silylative coupling (SC) of vinylcarbazole with vinyltrisubstituted silanes catalyzed by [RuH(Cl)(CO)(PCy3)2]. X-ray structures of two silylvinylcarbazoles as first N-vinylcarbazole derivatives have been resolved. The Pd-catalyzed Hiyama coupling reaction (also as the tandem reaction with SC) of synthesized (E)-N-(triethoxysilyl)vinylcarbazole with iodobenzene has been performed to afford (E)-N-(phenylvinyl)carbazole with high yield and stereoselectivity.     

Synthesis of donor-acceptor alkynylcyclopropanes by diastereoselective cyclopropanation of electron-deficient alkenes with alkoxyalkynyl Fischer carbene complexes

The reaction of electron-deficient alkenes with alkoxyalkynyl Fischer carbene complexes (FCCs) represents a straightforward route to a new type of captodative (donor-acceptor) alkynylcyclopropanes, which have been prepared in moderate to high yields and in a diastereoselective manner. Some studies regarding the employment of additives to facilitate the recovery of the metal moiety after the reaction are also described. Finally, the first example of a cyclopropanation reaction through employing Fischer carbene complexes under microwave irradiation is presented; this method proved to be an advantageous alternative to the thermal reaction.     

Synthesis of tetrahydroimidazo[1,5-b]-β-carboline derivatives with complex basic substituents

Novel tetrahydroimidazo[1,5-b]-β-carbolines derivatives 6 bearing complex basic chains as substituents on the imidic nitrogen have been prepared in a one-pot reaction. This simple experimental procedure overcomes the direct handle of isocyanates which can be favorably generated “in situ” from carbonyldiimidazole (CDI) and different amines. The stereochemistry of the novel compounds was determined by nmr experiments.     

Excess molar volumes and excess viscosities for then-hexane+dichloromethane+tetrahydrofuran ternary system at 25°C

Exces molar volumes, and excess viscosities of then-hexane+dichloromethane+tetrahydrofuran system have been determined at 25°C by measuring densities and viscosities. Different expressions exist in the literature to predict these excess properties from binary data. The empirical correlation of Cibulka is shown to be the best in this system.