The m/z 91 rearrangement ion in the mass spectra of some 1,4-benzodiazepines

With the aid of isotope labeling and by substituent shifts, the relatively strong m/z 91 ion in the mass spectra of 7-chloro-2-methoxy-5-phenyl-3H-1,4-benzodiazepine and related compounds was shown to contain the 5-phenyl ring and the 3-CH₂ group. Mechanisms involving the opening of the 7-membered ring and the migration of the phenyl ring from C-5 to C-3 are postulated for the formation of this ion. This rearrangement ion was also observed in the mass spectra of some 1-alkyl-7-chloro-1,3-dhydro-5-phenyl-2H-1,4-benzodiazepin-2-ones.     

A novel stereocontrolled synthesis of (z,z)-3,13-octadecadien-1-yl acetate,the sex pheromone of synanthedon species

Starting from 10-undecenoic acid, a stereocontrolled synthesis of (Z,Z)-3,13-octadecadien-1-yl acetate with high stereochemical purity was achieved by the use of Wittig-olefinations for the introductions of (Z)-double bonds.     

Synthesis of 9-azabicyclononanes from (z,z)-cycloocta-1,5-diene 1

The transannular N-heterocyclization of cycloocta-1-5-diene with NBS in the presence of cyanamide is a preparative useful method for the synthesis of 9-azabicyclononanes; a mixture of endo, endo-2,5-dibromo-N-azabicyclo[3.3.1]nonane is obtained in high yield.     

On the origin of the peaks of some substituted ions in the mass spectra of lecithins

Preliminary results concerning the origin of the peaks of some substituted ions in the mass spectra of lecithins, obtained under electron impact and chemical ionization conditions, are reported.     

Ion-chromatographic measurements of ammonium,fluoride, acetate,formate and methanesulphonate ions at very low levels in antarctic ice

Ion chromatography is used to determine the concentrations of organic (formate, acetate and methanesulphonate) and inorganic (fluoride and ammonium) ions present in Antarctic ice at less than 10⁻⁹ g g⁻¹ levels. With suitable columns, the simultaneous measurement of these ions requires only 6 min. A sample volume of 5 ml is sufficient to reach the 10⁻¹⁰ g g⁻¹ level. The determination of such low concentrations requires stringent contamination-free techniques. For formate and acetate, the samples should never come into contact with plastics. Except for methanesulphonate, all the ions studied can be produced by dissolution of the various gaseous compounds present in a polluted atmosphere. Therefore a glass device with pure nitrogen circulation was designed for air-free melting of samples. To prevent possible biological activity on organic matter, samples were analysed immediately after melting. Measurements of ammonium ion in these Antarctic ice samples demonstrate that the problem of contamination by surrounding ammonia was not completely eliminated in previous studies. The serious contamination problems encountered, particularly for carboxylic acids, cast doubt on some earlier results for remote areas.     

On the origin of some red soils from Sardinia (Italy): A neutron activation analysis investigation

In Sardinia, the Italian island in the middle of the MediterraneanSea, there are many red soils developed on limestone or dolomite. Soil andunderlying bedrock samples from 5 different sites have been submitted to chemicaland mineralogical characterization, by using standard X-ray diffraction analysis,spectrochemical methods and instrumental neutron activation analysis. Obtainedresults are presented and discussed in terms of precision and accuracy. Traceelement concentration variation with depth is discussed as well as the enrichment/depletionratios between soils and rocks, and the rare-earth element distribution. Dataanalysis suggests for some soils a formation process based on the evolutionof the underlying bedrock, and for the other soils a formation process partlybased on the evolution of the local rock but with meaningful contributionsof external sources, both eolian and/or alluvial.     

Electrophile and solvent dependent syntheses of cyclic ethers from (z,z)-cycloocta-1,-5-diene

The isomer ratio in the formation of disubstituted 9-oxabicyclo-[4.2.1]nonane and 9-oxabicyclo[3.3.1]nonane derivatives 2 and 3 by an oxyhalogenation procedure depends both on the electrophile and on the solvent utilized.     

An investigation on the nature of the peptide at m/z 904, overexpressed in plasma of patients with colorectal cancer and familial adenomatous polyposis

In an investigation devoted to the search for plasma markers for colorectal cancer (CRC), carried out by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry, a series of overexpressed peptides were identified in the plasma of patients. Among them the peptide with molecular weight 903 Da was the most abundant one, with a mean +/- (SD) relative abundance of 37 +/- 17% and a frequency over 60%. Interestingly, also in plasma samples of ten subjects affected by familial adenomatous polyposis (FAP), the peptide with molecular weight 903 was overexpressed. In this investigation, MALDI/MS/MS experiments were carried out on the ion at m/z 904 detected in the MALDI mass spectra of CRC and FAP patients. The data analysis by SwissProt.2007.01.09 indicates that this peptide is due to the sequence RPPGFSPF, found in the kininogen-1 precursor, which is an alpha-2-thiol proteinase inhibitor. In the case of subjects affected by a particular FAP syndrome, the MALDI/MS/MS spectra were quite different from those obtained from CRC and FAP patients. In fact, two sequences have been evidenced: RPPGFSPF belonging to kininogen-1 precursor, and PRKSSSSR belonging to Forkhead box protein 01A.     

Tris(dialkylamino)phosphine Chalcogenide Complexes of Tin(IV) Chloride: A Multinuclear (31P, 77Se,and 119Sn) NMR Characterization

Abstract

Four octahedral complexes of the type SnCl₄.2L [L = (R₂N)₃P(E): E = Se; R = Me(1), Et(2) and E = S; R = Me(3), Et(4)] have been studied in solution by multinuclear (³¹P, ⁷⁷Se, and ¹¹⁹Sn) NMR spectroscopy. ³¹P and ⁷⁷Se NMR data were informative of changes associated with complex formation. The solution structure of the complexes was confirmed by their ¹¹⁹Sn NMR spectra that showed two triplet features for each complex, attributed to a mixture of the expected cis and trans isomers. The triplet signal is due to the coupling with two equivalent phosphorus atoms, consistent with an octahedral geometry around the tin center. In addition, density functional theory (DFT)/B3LYP calculations have been carried out to support the interpretations of NMR data. The results are discussed and compared with those reported for related complexes.

GRAPHICAL ABSTRACT      

The influence of metal ions on the synthesis of MeAPO-5 (Me-Co,Mg) in the presence of acetate ions

Metal-substituted type 5 aluminophosphate structures have been prepared hydrothermally in a buffer solution consisting of acetic acid and a high concentration of template. The acetate ion added to the reaction mixture decreases the interaction of the metal ions with the gel and keeps the initial pH of the mother liquor. There was almost no change in the pH of the reaction mixture during the preparation. The most suitable pH range to synthesize single crystals of MeAPO-5 (Me = Co, Mg) was found to be around pH 5.5. The morphologies of the as-synthesized MeAPO-5 crystals were strongly dependent on the pH of the solution. The size of the crystals increased with increasing metal contents. Owing to the roles of acetate ions, MeAPO-5 crystals were obtained at high concentrations of template and metal ion. Increasing the amount of water and reducing the reaction temperature resulted in the formation of CHA-type structures.     

Cation exchange column chromatography in aqueous ammonium acetate: Separation of U(VI), Al(III), Sr(II), Ba(II) and Hg(II) from other metal ions

Summary A rigorous analysis of the effect of various concentrations (0.02–1.60M) of ammonium acetate on the distribution coefficients (K) of a number of metal ions using cation exchanger Dowex 50W-X8 (100–200 mesh NH₄ ⁺-form) has been made. On account of the low affinity of U(VI) for resin in 0.20M NH₄OAc it can be separated from all other metal ions. HighK values of Sr(II), Ba(II) and Hg(II) at higher 0.50M NH₄OAc are responsible for their separation from others. The abnormal column Chromatographic behaviour of Al(III) permits its separation from other metal ions including U(VI), Sr(II), Ba(II), Hg(II). A number of binary and ternary separations have been achieved.     

Selective detection of ferric,cobalt(II) and molybdate ions usingm-(Mercaptoacetamido)-phenol as a reagent

Summary m-(Mercaptoacetamido)phenol (m-MAP) is used for the selective and characteristic detection of ferric ion, cobalt and molybdate. The reagent produces deep green precipitate at pH 6 with ferric ion in the absence of tartrate, purple red precipitate with cobalt around pH 7 even in the presence of tartrate, and reduces molybdate to a yellow green to blue solution below pH 3. The sensitivity of the cobalt test is exceptionally high. The three elements can be tested in the presence of each other and the related metal ions.

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Zusammenfassung m-Merkapto-acetamidophenol (m-MAP) wurde für den selektiven Nachweis von Eisen(III), Kobalt und Molybdat herangezogen. Das Reagens gibt bei pH 6 mit Eisen(III) in Abwesenheit von Tartrat einen tiefgrünen Niederschlag, bei pH 7 mit Kobalt auch in Gegenwart von Tartrat einen purpurroten Niederschlag. Es reduziert Molybdat unter pH 3 und führt so zu einer gelb-grünen bis blauen Lösung. Die Empfindlichkeit des Kobaltnachweises ist besonders groß. Die drei Elemente können nebeneinander und in Gegenwart verwandter Metalle nachgewiesen werden.

     

Ethyl (benzothiazol-2-ylsulfonyl)acetate: a new reagent for the stereoselective synthesis of alpha,beta-unsaturated esters from aldehydes

The title reagent engaged in the modified Julia olefination with aldehydes under mild reaction conditions (DBU, CH(2)Cl(2), rt or -78 degrees C) to yield alpha,beta-unsaturated esters; aryl aldehydes and aliphatic aldehydes possessing significant chain branching elements gave trans alkene products with high stereoselectivity (E : Z up to >98 : 2), while straight chain aliphatic aldehydes gave cis products preferentially (Z : E up to 92 : 8).     

Synthesis of aliphatic insect pheromones from alicyclic starting materials: (Z)-6-heneicosen-11-one and (z)-8-dodecenyl acetate

Both (Z)-6-heneicosen-11-one, the pheromone of Douglas fir tussock moth, and (Z)-8-dodecenyl acetate, the pheromone of oriental fruit moth, have been synthesized from cyclohexane-1,3-dione.     

The preparation and 119Sn and 19F NMR spectra of some trifluoromethylphenyltin(IV) compounds

The preparation of a series of new trifluoromethylphenyltin(IV) compounds, Bu_nSn(C₆H₄CF₃-3)_4-n, (C₆H₄CF₃-3)SnCl₃, (C₆H₄CF₃-2)SnCl₃, and some related adducts with 2,2¹-bipyridyl and 1,10-phenanthroline, is described. ¹¹⁹Sn and ¹⁹F chemical shifts have been determined, together with values of J(¹¹⁹Sn=F) and ³J(¹¹⁹Sn=H_itortho), and the possibility of a “through space” tinfluorine coupling mechanism is also discussed.     

Formation, isolation, spectroscopic properties, and calculated properties of some isomers of C(60)H(36)

Isomers of C(60)H(36) and He@C(60)H(36) have been synthesized by the Birch or dihydroanthracene reduction of C(60) and isolated by preparative high-pressure liquid chromatography. (3)He, (13)C, and (1)H NMR spectroscopic properties were then determined. A comparison of experimental chemical shifts against those computed using density functional theory (B3LYP) with polarized triple- and double-zeta basis sets for He and C,H, respectively, allowed provisional assignment of structure for several isomers to be made. Theoretical calculations have also been carried out to identify low-energy structures. The transfer hydrogenation method using dihydroanthracene gives a major C(60)H(36) isomer and a minor C(60)H(36) isomer with C(3) symmetry as determined by the (13)C NMR spectrum of C(60)H(36) and the (3)He NMR spectrum of the corresponding sample of (3)He@C(60)H(36). In view of the HPLC retention times and the (3)He chemical shifts observed for the Birch and dihydroanthracene reduction products, the two isomers generated by the latter procedure can be only minor isomers of the Birch reduction. A significant energy barrier apparently exists in the dihydroanthracene reduction of C(60) for the conversion of the C(3) and C(1) symmetry isomers of C(60)H(36) to the T symmetry isomer previously predicted by many calculations to be among the most stable C(60)H(36) isomers. Many of the (1)H NMR signals exhibited by C(60)H(36) (and C(60)H(18), previously reported) are unusually deshielded compared to "ordinary" organic compounds, presumably because the unusual structures of C(60)H(36) and C(60)H(18) result in chemical shift tensors with one or more unusual principal values. Calculations clearly show a relationship between exceptionally deshielded protons beta to a benzene ring in C(60)H(18) and C(60)H(36) and relatively long C-C bonds associated with these protons. The additional information obtained from 1D and 2D (1)H NMR spectra obtained at ultrahigh field strengths (up to 900 MHz) will serve as a critical test of chemical shifts to be obtained from future calculations on different C(60)H(36) isomers.