α‐ and β‐Lipomycin: Total Syntheses by Sequential Stille Couplings and Assignment of the Absolute Configuration of All Stereogenic Centers |
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Authors: | Dr Max L Hofferberth Prof Dr Reinhard Brückner |
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Institution: | Institut für Organische Chemie, Albert‐Ludwigs‐Universit?t Freiburg, Albertstrasse 21, 79104 Freiburg (Germany) http://www.brueckner.uni‐freiburg.de |
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Abstract: | 40 years ago spectroscopy, derivatization, and degradation revealed the structures of α‐lipomycin and its aglycon β‐lipomycin except for the configurations of their side‐chain stereocenters. We synthesized all relevant β‐lipomycin candidates: the (12R,13S) isomer has the same specific rotational value as the natural product. By the same criterion the (12R,13S)‐configured D ‐digitoxide is identical to α‐lipomycin. We double‐checked our assignments by degrading α‐ and β‐lipomycin to the diesters 33 and 34 and proving their 3D structures synthetically. |
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Keywords: | configuration determination cross‐coupling natural products polyenes tetramic acids |
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