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- Title
Total Synthesis and Absolute Configuration of Epicoccamide D, a Naturally Occurring Mannosylated 3-Acyltetramic Acid.
- Authors
Loscher, Sebastian; Schobert, Rainer
- Abstract
The endofungal metabolite epicoccamide D was synthesised in eighteen steps and 17 % yield as the first member of the family of natural glycotetramic acids. The modular character of the synthesis opens access also to analogues featuring different sugars and spacers. It comprises several high-yielding key steps. The β- D-mannosyl group was introduced by using an α- D-glucosyl imidate donor with subsequent oxidative-reductive epimerisation at C-2′. The pyrrolidine ring was closed quantitatively by a Lacey-Dieckmann condensation of an N-(β-ketoacyl)- N-methyl alaninate. The resulting 3-[ω-(β- D-mannosyl)octadec-2-enoyl]tetramic acid was hydrogenated in the presence of the rhodium catalyst ( R, R)-[Rh(Et-DUPHOS)][BF4] to establish the (7 S)-stereocentre. This was possible only after blocking the acyltetramic acid as a BF2-chelate to prevent capture of the metal catalyst. We also assigned the hitherto unknown configuration of the natural product as being 5 S,7 S by comparison of its 13C NMR spectroscopic and optical rotation data with those of our two synthetic 5 S,7 R/ S-diasteromers.
- Subjects
CHEMICAL synthesis; RHODIUM catalysts; PYRROLIDINE; PLATINUM group catalysts; METAL catalysts
- Publication
Chemistry - A European Journal, 2013, Vol 19, Issue 32, p10619
- ISSN
0947-6539
- Publication type
Article
- DOI
10.1002/chem.201301914