A chiral crown ether Is successfully used as a pseudo stationary phase In capillary zone electrophoresis to separate optically active amines. On the basis of the results obtained from the separation of more than 20 amines, two recognition mechanisms are proposed: (I) the four crown ether substituents act as chiral barriers for the guest molecules and (II) lateral electrostatic Interactions occur between host and guest. These results are confirmed by thermodynamic studies on the hostguest complexes. Best resolutions are achieved If the chiral center Is adjacent to the amine functionality. However, even racemates with a chiral center In the ^-position to the amine could be resolved excellently. For the separation of aliphatic amino acids a method has been developed allowing detection by an Indirect detection mode.
Marked for life. For the characterization of larger proteins new NMR spectroscopy methods that focus on side‐chain methyl groups have been developed by using selectively isotope‐labeled precursor compounds. Here we report on the synthesis of a 13C‐methyl‐group‐labeled methionine precursor on a preparative scale, and its incorporation into the SH2 domain of the protein PLC‐γ1 (see scheme).
More than six decades after proposing copper acetylide, Cu2C2, as catalytically active species in ethynylation reactions by Walter Reppe, the explosive species have been experimentally identified and investigated during catalysis in detail now. Taking into account specific safety precautions, unequivocal qualitative characterization was achieved by Raman spectroscopy and X‐ray powder diffraction of supported copper catalysts Cu/Bi/SiO2 during and after activation and catalysis in comparison to bulk Cu2C2 materials. Quantification of Cu2C2 succeeded by thermal analysis and Raman spectroscopy. Its formation in aqueous suspension is studied starting from copper(II) oxide catalysts including dissolution, reduction and precipitation steps. Copper acetylide formation can be correlated with catalytic performance in the ethynylation of formaldehyde to 1,4‐butynediol.
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