Synlett 1999; 1999(S1): 893-896
DOI: 10.1055/s-1999-3103
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Site-Selective Epimerization of a Fungal Cyclodepsipeptide via a 5-Aminooxazole Intermediate

Berndt Oberhauser* , Karl Baumann, Brigitte Grohmann, Hildegard Sperner
  • *Novartis Forschungsinstitut GmbH, Brunner Str. 59, A-1235 Wien, Austria; Fax +43(1)86 63 43 54; E-mail: [email protected]
Further Information

Publication History

Publication Date:
31 December 1999 (online)

The epimerization of the cyclic depsiheptapeptide 1 at a single amino acid (Leu) was achieved in four steps. After regio-selective thionation of 1 at one of its six amide-bonds, subsequent S-benzylation of the thioamide 2 led to the thioimidate 3, which was converted to the peptide-bridged 5-aminooxazole 5 by an unusual mercury promoted intramolecular cyclization. Re-opening of the oxazole ring by acid hydrolysis regenerated the parent cyclopeptolide framework 6, but preferentially with inverted configuration at leucine.