title: α- and β-Lipomycin: total syntheses by sequential stille couplings and assignment of the absolute configuration of all stereogenic centers.
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.
authors.affiliation: Institut für Organische Chemie, Albert-Ludwigs-Universität Freiburg, Albertstrasse 21, 79104 Freiburg (Germany) http://www.brueckner.uni-freiburg.de.
authors.forename: Max L
authors.initials: ML
authors.lastname: Hofferberth
authors.forename: Reinhard
authors.initials: R
authors.lastname: Brückner
keywords: configuration determination; cross-coupling; natural products; polyenes; tetramic acids