Electron impact induced intramolecular hydrogen transfer reactions in polymethylene glycol di-p-toluenesulfonates
摘要:
AbstractThe mechanisms of formation of the ionized acid and the protonated acid fragments in the electron impact induced fragmentation of the title compounds were investigated. The well known mechanisms of hydrogen transfer through mono‐ and bicyclic transition states that occur in the molecular ions of carboxylic esters are not the main pathways giving rise to these fragments. The major component of the m/z 172 peak corresponding formally to ionized p‐toluenesulfonic acid in fact has a different structure; its formation involves a complex mechanism including a double hydrogen transfer reaction.
The Asymmetric Synthesis of the [D8]-Labeled (−)-(S)-Dihydroxyverbacine, the Terminal Precursor in the Biogenesis of the Macrobicyclic Spermine Alkaloids Aphelandrine and Orantine
The asymmetricsynthesis of the unlabeled and [D8]-labeled terminal precursors, 4 ((−)-(S)-dihydroxyverbacine) and 19, respectively, in the biogenesis of the spermine alkaloids aphelandrine (5) and orantine (6), respectively, is described. A partial synthesis of the alkaloid (−)-(S)-[(E)-4-methoxycinnamoyl]buchnerine (10) is also presented.
Development of an isotope-coded activity-based probe for the quantitative profiling of cysteine proteases
作者:Paul F. van Swieten、Rene Maehr、Adrianus M.C.H. van den Nieuwendijk、Benedikt M. Kessler、Michael Reich、Chung-Sing Wong、Hubert Kalbacher、Michiel A. Leeuwenburgh、Christoph Driessen、Gijsbert A. van der Marel、Hidde L. Ploegh、Herman S. Overkleeft
DOI:10.1016/j.bmcl.2004.04.046
日期:2004.6
Quantification studies of complex protein mixtures have been restricted mainly to whole cell extracts. Here we describe the synthesis of two sets of isotope-coded activity-based probes that allow quantitative functional proteomics experiments on the cathepsins. (C) 2004 Elsevier Ltd. All rights reserved.
The Enantiomerization Barrier of 5-Methyl-cyclohepta-1,2,4,6-tetraene
作者:Ralf Warmuth
DOI:10.1021/ja015743e
日期:2001.7.1
Structure−Property Correlations in Model Compounds of Oligomer Liquid Crystals
orientational order parameters, bond conformations, and molecular dimensions. For the dimers in particular, the solute shapes were estimated from phase diagrams of the dimer/MBBA systems, the crystalstructures were determined by X-ray diffraction, and the melting points and enthalpies of fusion were evaluated from DSC measurements. From the dimers, the so-called odd−even effect was clearly observed in not only