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84.
The 70 eV mass spectra of a number of 13C- and D-labelled analogs of 1-heptene have been measured, as well as the metastable transitions in the non-labelled compound. Isotopic distributions in the major fragment ions have been calculated from the high and low resolution data. The results show that considerable skeletal rearrangement must take place before formation of most of the fragment ions. Loss of methyl and ethyl radicals occurs mainly from the two ends of the molecule. Ethylene fragments come primarily from the unsaturated end of the molecule, but show evidence of significant prior skeletal rearrangement. The predicted McLafferty rearrangement accounts for only 2/3 of the C4H8+ ions formed, less for the C3H6+ ions. At least 80% of C4H9+ ions appear to be formed by allylic cleavage, as expected, but this mechanism can only account for a maximum of 20% of the formation of the complementary ion C3H5+. Both, this latter ion and C3H6+, are probably generated by loss of hydrogen from C3H7+. Figures obtained for label retention in 1-[13C]- and 1-D-labelled analogs were nearly identical for most fragment ions, probably indicating that the hydrogen atoms in position 1 remain on C(1) even following skeletal rearrangement. A similar result was found for the 7-[13C]- and 7-D-labelled compounds. The main exceptions in the case of the products labelled in position 1 (C4H7+, C3H3+) seem to be due to initial loss of an hydrogen atom from this position followed by further fragmentation. 相似文献
85.
Yao M Mantha S Shah VR Vachharajani NN Arnold ME Pursley JM Srinivas NR 《Biomedical chromatography : BMC》2002,16(3):175-182
A high performance liquid chromatographic-mass spectrometric (LC/MS) assay was developed and validated for the determination of BMS-204352 in dog K(3)EDTA plasma. A 0.5 mL aliquot of control plasma was spiked with BMS-204352 and internal standard (IS) and buffered with 1 mL of 5 mM ammonium acetate. The mixture was then extracted with 3 mL of toluene. After separation and evaporation of the organic phase to dryness using nitrogen at 40 degrees C, the residue was reconstituted in the mobile phase and 25 microL of the sample were injected onto a Hypersil C(18) column (2 x 50 mm; 3 microm) at a flow rate of 0.5 mL/min. The mobile phase was consisted of two solvent mixtures (A and B). Solvent A was composed of 5 mM ammonium acetate and 0.1% triethylamine in 75:25 v/v water:methanol, pH adjusted to 5.5 with glacial acetic acid, and solvent B was 5 mM ammonium acetate in methanol. A linear gradient system was used to elute the analytes. The mass spectrometer was programmed to admit the de-protonated molecules at m/z 352.7 (IS) and m/z 357.9 (BMS-204352). Standard curves of BMS-204352 were linear (r(2) > or = 0.998) over the concentration range of 0.5-1000 ng/mL. The mean predicted quality control (QC) concentrations deviated less than 5.1% from the corresponding nominal values (ie 4, 80, 400 and 2000 ng/mL); the within- and between-assay precision of the assay were within 5.5% relative standard deviation. Stability of BMS-204352 was confirmed after at least three freeze/thaw cycles and BMS-204532 was stable in dog plasma when stored frozen at or below -20 degrees C for at least 16 weeks in spiked QC samples and for at least 4 1/2 weeks for in vivo study samples. BMS-204352 and IS were stable in the injection solvent at room temperature for at least 24 h. The assay was applied to delineate the pharmacokinetic disposition of BMS-204352 in dogs following a single intravenous dose administration. In conclusion, the assay is accurate, precise, specific, sensitive and reproducible for the pharmacokinetic analysis of BMS-204532 in dog plasma. 相似文献
86.
Levels of138Ce and140Nd have been studied using the138Ba(α,4nγ)138Ce and140Ce(α, 4nγ)140Nd reactions. Singleγ-ray spectra,γ-γ coincidence spectra, angular and time distributions with respect to the beam bursts have been measured. A number of higher excited states with excitation energies up to about 5 MeV and with spin value up to 12 are populated in both nuclei. The lower states with spins and parities 7?, 5?, 6? and 10+ can be explained by two-quasiparticle neutron configurations of the types (h 11/2 ?1 ,d 3/2 ?1 ) 7? , (h 11/2 ?1 ,S 1/2 ?1 ) 5?, 6? and (h 11/2 ?2 ) 10+. Several high-spin states observed in138Ce and140Nd can be explained qualitatively as four-quasiparticle states with two-proton-two-neutron configurations. The 3? state at an energy of 2,137.4 keV is observed in138Ce. The evidence for the existence of the low-lying 3? states in140Nd at 2,124.0 keV is discussed. Beside the known 9.6 ms (7?) isomeric state in138Ce another state at 3,538.5keV (10+) with a half life of about 200 ns has been observed. The observed levels in the138Ce and140Nd nuclei are compared with theoretical predictions using delta force interaction. 相似文献
87.
Mthandazo Dube Dayma Llanes Mohamad Saoud Robert Rennert Peter Imming Ccile Hberli Jennifer Keiser Norbert Arnold 《Molecules (Basel, Switzerland)》2022,27(9)
Neglected tropical diseases affect the world’s poorest populations with soil-transmitted helminthiasis and schistosomiasis being among the most prevalent ones. Mass drug administration is currently the most important control measure, but the use of the few available drugs is giving rise to increased resistance of the parasites to the drugs. Different approaches are needed to come up with new therapeutic agents against these helminths. Fungi are a source of secondary metabolites, but most fungi remain largely uninvestigated as anthelmintics. In this report, the anthelmintic activity of Albatrellus confluens against Caenorhabditis elegans was investigated using bio-assay guided isolation. Grifolin (1) and neogrifolin (2) were identified as responsible for the anthelmintic activity. Derivatives 4–6 were synthesized to investigate the effect of varying the prenyl chain length on anthelmintic activity. The isolated compounds 1 and 2 and synthetic derivatives 4–6, as well as their educts 7–10, were tested against Schistosoma mansoni (adult and newly transformed schistosomula), Strongyloides ratti, Heligmosomoides polygyrus, Necator americanus, and Ancylostoma ceylanicum. Prenyl-2-orcinol (4) and geranylgeranyl-2-orcinol (6) showed promising activity against newly transformed schistosomula. The compounds 1, 2, 4, 5, and 6 were also screened for antiproliferative or cytotoxic activity against two human cancer lines, viz. prostate adenocarcinoma cells (PC-3) and colorectal adenocarcinoma cells (HT-29). Compound 6 was determined to be the most effective against both cell lines with IC50 values of 16.1 µM in PC-3 prostate cells and 33.7 µM in HT-29 colorectal cells. 相似文献
88.
In life sciences,molecules are categorized into biological macromolecules(protein,DNA,RNA etc.)and small molecules(neurotransmitters,vitamins,drugs,natural products,water etc.).The main methodology of chemistry for life sciences is using chemical techniques and tools to explore and manipulate the functions of biological macromolecules.This methodology can be traced back to W hler’s synthesis of urea from"inorganic"compounds in 1828.Today,we realize that chemistry can advance a molecular understanding of biology,and the harnessing of biology can advance chemical knowledge as well[1–4].Chemicals are widely used as probes to investigate biological functions[5–7]. 相似文献
89.
An efficient and chemoselective method for the Friedel–Crafts acylation of aromatic compounds using P2O5/Al2O3 and carboxylic acids. Both aromatic and aliphatic carboxylic acids reacted easily to afford the corresponding aromatic ketones in good yields. 相似文献
90.
Reduction of phenyl-substituted pyridinium methoiodides with sodium borohydride in water afforded besides the desired tetrahydropyridines substantial amounts of amine-borane complexes. Reduction in methanol afforded tetrahydropyridines in high yield, with almost no amine-boranes formed. 相似文献