Fluorescence labelling of carbohydrates with 2-aminobenzamide (2AB)

2-Aminobenzamide (2AB) is a common fluorescence label attached to reducing oligosaccharides by a reductive amination procedure. Chemical investigation of the published literature procedure reveals labelling occurs by the expected mechanism for both protected and unprotected glucose derivatives to yield open-chain carbohydrates rather than result in the formation of any heterocyclic materials. Pentenyl glucosides may also be readily attached to the 2AB label by a sequence of dihydroxylation, periodate cleavage and subsequent reductive amination of the resulting aldehyde. 2AB labelling is compatible with deprotection of both acetate and benzyl protecting groups.     

A tandem mass spectrometric investigation of N-(3-ferrocenyl-2-naphthoyl) dipeptide ethyl esters and N-(6-ferrocenyl-2-naphthoyl) dipeptide ethyl esters

N‐(3‐Ferrocenyl‐2‐naphthoyl) dipeptide ethyl esters 1–4 and N‐(6‐ferrocenyl‐2‐naphthoyl) dipeptide ethyl esters 5–8 were prepared by coupling either 3‐ferrocenylnaphthalene‐2‐carboxylic acid or 6‐ferrocenylnaphthalene‐2‐carboxylic acid to the dipeptide ethyl esters GlyGly(OEt) (1, 5), AlaGly(OEt) (2, 6), GlyPhe(OEt) (3, 7) and GlyLeu(OEt) (4, 8), using the standard N‐(3‐dimethylaminopropyl)‐N'‐ethylcarbodiimide hydrochloride, 1‐hydroxybenzotriazole protocol. Electrospray ionization mass spectrometry (ESI‐MS) and laser desorption ionization mass spectrometry (LDI‐MS) were employed in conjunction with tandem mass spectrometry in the analysis of N‐(3‐ferrocenyl‐2‐naphthoyl) dipeptide ethyl esters 1–4 and N‐(6‐ferrocenyl‐2‐naphthoyl) dipeptide ethyl esters 5–8. Radical cations, [M]^+? and [M + H]⁺ species were both observed in the mass spectra. Intense sodium [M + Na]⁺ and potassium [M + K]⁺ adducts were also present. An important diagnostic ion at m/z [M–65]⁺ was observed in both the MS and MS/MS spectra of the N‐(3‐ferrocenyl‐2‐naphthoyl) dipeptide derivatives. Sequence‐specific ions were generally not observed in the MS/MS spectra of the N‐(3‐ferrocenyl‐2‐naphthoyl) series due to formation of the diagnostic [M–65]⁺ ion. Sequence‐specific ions were observed in the MS/MS spectra of the N‐(6‐ferrocenyl‐2‐naphthoyl) dipeptide esters with charge retention on the derivatized N‐terminal of the dipeptide. Both series of compounds could be successfully analyzed by MALDI without the use of a matrix (LDI). Copyright © 2011 John Wiley & Sons, Ltd.     

“Age” determination of irradiated materials utilizing inductively coupled plasma mass spectrometric (ICP-MS) detection

A gas pressurized extraction chromatography (GPEC) system has been developed to perform elemental separations on radioactive samples to determine total and isotopic compositions of Cs and Ba from an irradiated salt sample, fuel sample and two sealed radiation sources. The GPEC system employs compressed nitrogen to move liquid through the system, compared to gravity or pumped liquids that are typically used for separations. A commercially available Sr-Resin™ was used to perform the separation for the above mentioned analytes. A 1% acetic acid solution was determined to be the best extractant for Ba. A flow rate of 0.1 mL/min was determined to be optimal for the separation of Ba. Complete recovery of the Cs and Ba was achieved, within the systematic uncertainties of the experiments.     

Synthesis and structure determination of N-(alkoxycarbonylsulfenyl)-s-triazine herbicides

Various 2-substituted-4,6-bis(alkylamino)-1,3,5-triazines, 1 , have been found to react with alkoxycarbonylsulfenyl chlorides, 2 , to give the title compounds, 3 . The structural characterization of 3a in the solid state by single X-ray crystallographic analysis established that it is the isomer wherein the methoxycarbonylthio group is attached to the less sterically hindered, exocyclic nitrogen bearing the ethyl group.     

Synthesis and physical properties of N-2-phenylethyl- and N-2-(3-indolyl)ethyl-5′-deoxy-5′-adenosineacetamides

The synthesis and physical properties of N-2-phenylethyl- and N-2-(3-indolyl)ethyl-5′-deoxy-5′-adenosineacetamides ( 2 and 3 ), which are stable compounds of phenylalanyl- and tryptophanyl-AMPs, are described.     

The molecular and crystal structure of N-(4-n-butyloxybenzylidene)-4'-ethylaniline (4O.2) and N-(4-n-heptyloxybenzylidene)-4'-hexylaniline (7O.6)

757047134     

Improved liquid chromatographic determination of nine currently used (fluoro)quinolones with fluorescence and mass spectrometric detection for environmental samples

An HPLC method using C18-modified silica as stationary phase has been developed for environmental trace analysis of nine (fluoro)quinolones. Detection is done by fluorescence measurement or MS using the modes of SIM and selected reaction monitoring (SRM). Best separation is achieved with a gradient consisting of 50 mM formic acid and methanol, which is fully compatible with MS coupling. LOQs (S/N of 10) for fluorescence detection are between 10 and 60 microg/L, depending on the analyte. MS detection (SIM and SRM) yields LOQs that are better by a factor of at least an order of magnitude. Sample preconcentration and sample clean-up is accomplished by SPE (preconcentration factor of 1000), leading to LOQs in the low ng/L range. Recoveries of the preconcentration procedure are better than 80% for all analytes. The suitability for real samples has been demonstrated by analyzing surface waters, municipal waste waters, sewage treatment plant effluents, sewage sludge, and sediment taken from rivers and fish ponds. The method should also be useful for determination of residues of (fluoro)quinolones in food or other matrices. The degradation of the (fluoro)quinolones has been examined over 5 days in order to get information about the decomposition rate and the degradation products eventually occurring in the environment.     

New designer drugs N-(1-phenylcyclohexyl)-2-ethoxyethanamine (PCEEA) and N-(1-phenylcyclohexyl)-2-methoxyethanamine (PCMEA): Studies on their metabolism and toxicological detection in rat urine using gas chromatographic/mass spectrometric techniques

Studies are described on the metabolism and the toxicological detection of the phencyclidine-derived designer drugs N-(1-phenylcyclohexyl)-2-ethoxyethanamine (PCEEA) and N-(1-phenylcyclohexyl)-2-methoxyethanamine (PCMEA) in rat urine using gas chromatographic/mass spectrometric (GC/MS) techniques. The identified metabolites indicated that PCEEA and PCMEA were transformed to the same metabolites by N-dealkylation and O-dealkylation partially followed by oxidation of the resulting alcohol to the respective carboxylic acid and hydroxylation of the cyclohexyl ring at different positions and combinations of those. Finally, aromatic hydroxylation of the O-dealkylated metabolites was partially followed by hydroxylation of the cyclohexyl ring at different positions. All metabolites were partially excreted in conjugated form. The authors' systematic toxicological analysis (STA) procedure using full-scan GC/MS after acid hydrolysis, liquid-liquid extraction and microwave-assisted acetylation allowed the detection of an intake of a common drug users' dose both of PCEEA and PCMEA in rat urine. Assuming similar metabolism in humans, the STA should be suitable for proof of an intake of PCEEA and PCMEA in human urine, although their differentiation is not possible due to common metabolites.     

Derivatization procedures for the detection of beta(2)-agonists by gas chromatographic/mass spectrometric analysis

An evaluation of derivatization procedures for the detection of beta(2)-agonists is presented. The study was performed with the beta(2)-agonists bambuterol, clenbuterol, fenoterol, formoterol, salbutamol, salmeterol and terbutaline. Different derivatizating agents were employed, aiming to obtain derivatives with high selectivity to be used in the gas chromatographic/mass spectrometric analysis of beta(2)-agonists in biological samples. Trimethylsilylation was compared with different agents and the role of some catalysts was evaluated. Acylation, combined trimethylsilylation and acylation, and the formation of cyclic methylboronates were also studied. Sterical hindrance caused by different substituents at the nitrogen atom of the beta-ethanolamine lateral chain of beta(2)-agonist molecules is mainly responsible for differences in the abundances of the derivatives obtained. The use of catalysts produces an increase in the derivatization yield, especially for compounds with low steric hindrance (substituents with primary and secondary carbon atoms). The formation of trimethylsilyl (TMS) ethers is not influenced by structural molecular differences when only hydroxy groups are involved in derivatization. Combined trimethylsilylation and acylation showed that compounds with a secondary carbon atom linked to the nitrogen atom form mainly N-TFA-O-TMS derivatives, with a small amount of N-TMS-O-TMS derivatives. Compounds with tert-butyl substituents at the amino group (bambuterol, salbutamol and terbutaline) formed O-TMS derivatives as the main products, although a limited amount of trifluoroacylation at the nitrogen atom also occurred. Cyclic methylboronates were formed with bambuterol, clenbuterol, formoterol, salbutamol and salmeterol. Owing to hydroxy substituents in unsuitable positions for ring formation, this procedure was not effective for fenoterol and terbutaline. Mass spectra of different derivatives and tentative fragmentation profiles are also shown. For screening purpose (e.g. sports drug testing), derivatization with MSTFA or BSTFA alone is recommended as a comprehensive derivatization technique for beta(2)-agonists owing to minimal by-product formation; formation of cyclic methylboronates can be useful for confirmation purposes. Detection limits were obtained for the TMS and cyclic methylboronate derivatives using the derivatizing reagents MSTFA and trimethylboroxine, respectively. For most of the compounds, lower detection limits were found for the TMS derivatives.     

Separation and determination of alkylglycosides by liquid chromatography with electrospray mass spectrometric detection

The separation of alkylpolyglycosides by liquid chromatography with electrospray mass spectrometric detection, using either an alkylamide or a cyanopropyl column, and acetonitrile/water mixtures as mobile phases, was developed. Using the alkylamide column and isocratic elution, the α- and β-epimers and ring isomers (pyranosides and furanosides) of the alkylmonoglycosides were resolved. The ring isomers were also resolved in a much shorter time using the cyanopropyl column with gradient elution. Using these columns, the isomers of the alkyldiglycosides and alkyltriglycosides were also partially resolved. The equilibration time was much shorter with the cyanopropyl column, which was selected to perform quantitation studies. The response factors increased more than an order of magnitude with the length of the alkyl chain, from the methyl to the decylmonoglycoside, and decrease largely for the dodecyl and tetradecylmonoglycoside. The limits of detection were of ca. 25 μM from the hexyl up to the dodecylmonoglycoside. The procedures were applied to the characterisation and determination of alkylmonoglycosides in toiletries.     

Quantum dots assisted laser desorption/ionization mass spectrometric detection of carbohydrates: qualitative and quantitative analysis

A quantum dots (QDs) assisted laser desorption/ionization mass spectrometric (QDA‐LDI‐MS) strategy was proposed for qualitative and quantitative analysis of a series of carbohydrates. The adsorption of carbohydrates on the modified surface of different QDs as the matrices depended mainly on the formation of hydrogen bonding, which led to higher MS intensity than those with conventional organic matrix. The effects of QDs concentration and sample preparation method were explored for improving the selective ionization process and the detection sensitivity. The proposed approach offered a new dimension to the application of QDs as matrices for MALDI‐MS research of carbohydrates. It could be used for quantitative measurement of glucose concentration in human serum with good performance. The QDs served as a matrix showed the advantages of low background, higher sensitivity, convenient sample preparation and excellent stability under vacuum. The QDs assisted LDI‐MS approach has promising application to the analysis of carbohydrates in complex biological samples. Copyright © 2016 John Wiley & Sons, Ltd.     

High sensitivity determination of valproic acid in mouse plasma using semi-automated sample preparation and liquid chromatography with tandem mass spectrometric detection

A high-throughput liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) assay using automated sample preparation has been developed for the determination of valproic acid (VPA) in mouse plasma. A liquid-handling system was programmed to prepare calibration standard solutions in plasma, as well as quality controls and clinical samples. Plasma protein precipitation was performed on a 96-well plate, and the collected supernatant was directly injected into a reversed-phase LC/ESI-MS/MS system in the negative ionization mode. The calibration curve for VPA was linear over a dynamic range of 0.15-100 microg/mL. The limit of detection was 75 ng/mL and the lower limit of quantitation was 150 ng/mL. Intra- and inter-day validation assays of the semi-automated plasma analysis showed satisfactory accuracy and precision.     

Nickel(II) and copper(II) complexes of 2-acetylpyridine 4 N-(2-methylpyridinyl)-, 4 N-(2-ethylpyridinyl)- and 4 N-methyl(2-ethylpyridinyl) thiosemicarbazones

Summary Ni^II and Cu^II complexes of 2-acetylpyridine ⁴ N-(2-methylpyridinyl)-, ⁴ N-(2-ethylpyridinyl)- and ⁴ N-methyl(2-ethylpyridinyl) thiosemicarbazones (HL4pam, HL4pae, and HL4Mpae, respectively) of general formula [M(HL)X₂] have been isolated from boiling EtOH and characterized by physico-chemical and spectroscopic methods. The growth inhibition activities of the thiosemicarbazones and their complexes were measured against Aspergillus nicer and Paecilomyces variotii.     

Investigation of the stereodirection of the Ritter reaction. Crystalline and molecular structure of N-(2-phenethyl)-4-methylpiperid-4-ol and N-(2-phenethyl)-4-methyl-4-acetamido-piperidine

The stereodirection of the Ritter reaction of N-(2-phenethyl)-4-methylpiperid-4-ol to the corresponding amide has been studied. X-ray analysis has shown that the reaction occurs with retention of the configuration about atom C₄ of the piperidine ring. Attempts are made to explain the stereodirection of the direction.A. L. Mndzhoyan Institute of Fine Organic Chemistry, Armenian Academy of Sciences, Yerevan 375014. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1391–1396, October, 1994. Original article submitted September 28, 1994.     

Pd-Cu-catalyzed synthesis of N-(2E,4)- and N-(2Z,4)-enyne cyclic amines

By Pd-Cu-catalyzed coupling of (2E)- and (2Z)-3-chloroprop-2-en-1-ylamines and alkynes a stereoselective method of the synthesis was developed for a series of (2E,4)- and (2Z,4)-enyne cyclic amines.     

Synthesis and structure of N-(4-dialkylaminophenyl)hexafluoro-1,4-naphthoquinone 4-imines

The reaction of heptafluoro-1-naphthol with N,N-dialkyl-p-nitrosoanilines or N,N-dialkyl-p-phenylenediamines in the presence of HIO₃ gave the corresponding polyfluorinated N-aryl-1,4-naphthoquinone 4-imine derivatives which exist in solution as equilibrium mixtures of Z and E isomers. 2,3,5,6,7,8-Hexafluoro-N-(4-dimethylaminophenyl)-1,4-naphthoquinone 4-imine in crystal has exclusively the Z-isomer structure.     

Mass spectrometric determination of the configuration of 2-methyl-and 1,2-dimethyl-4-vinyl-ethinyl(n-butyl)-4-hydroxyperhydroquinolines

The configuration at C-2 and C-4 in the molecules of 2-methyl- and 1,2-dimethyl-4-vinylethinyl(n-butyl)-4-hydroxyperhydroquinolines was determined by mass spectrometry. The principal conclusions concerning the stereochemistry were made on the basis of differences in the values of the I_[M?15]⁺/I_[M]⁺·, I_[M?17]⁺/I_[M]⁺·, I[_M?43]⁺/I_[M]⁺· and I_[M?57]⁺/I_[M]⁺· ratios in the mass spectra of the epimeric vinylethinylic alcohols, and of the I_[M?15]⁺/I_[M]⁺· and I_[M?15]⁺/I_[M]⁺· ratios in the case of the n-butylic alcohols.