Total synthesis and absolute configuration of epicoccamide D, a naturally occurring mannosylated 3-acyltetramic acid. 2013

Sebastian Loscher, and Rainer Schobert
Organic Chemistry Laboratory, University Bayreuth, Universitaetsstrasse 30, NW 1, 95447 Bayreuth, Germany.

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 (7S)-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 5S,7S by comparison of its (13) C NMR spectroscopic and optical rotation data with those of our two synthetic 5S,7R/S-diasteromers.

UI MeSH Term Description Entries
D008358 Mannose A hexose or fermentable monosaccharide and isomer of glucose from manna, the ash Fraxinus ornus and related plants. (From Grant & Hackh's Chemical Dictionary, 5th ed & Random House Unabridged Dictionary, 2d ed) D-Mannose,Mannopyranose,Mannopyranoside,D Mannose
D008362 Mannosides Glycosides formed by the reaction of the hydroxyl group on the anomeric carbon atom of mannose with an alcohol to form an acetal. They include both alpha- and beta-mannosides. Mannoside
D011760 Pyrrolidinones A group of compounds that are derivatives of oxo-pyrrolidines. A member of this group is 2-oxo pyrrolidine, which is an intermediate in the manufacture of polyvinylpyrrolidone. (From Merck Index, 11th ed) Pyrrolidinone,Pyrrolidone,Pyrrolidones
D002384 Catalysis The facilitation of a chemical reaction by material (catalyst) that is not consumed by the reaction. Catalyses
D006001 Glycoconjugates Carbohydrates covalently linked to a nonsugar moiety (lipids or proteins). The major glycoconjugates are glycoproteins, glycopeptides, peptidoglycans, glycolipids, and lipopolysaccharides. (From Biochemical Nomenclature and Related Documents, 2d ed; From Principles of Biochemistry, 2d ed) Glycoconjugate
D006865 Hydrogenation Addition of hydrogen to a compound, especially to an unsaturated fat or fatty acid. (From Stedman, 26th ed) Hydrogenations
D001688 Biological Products Complex pharmaceutical substances, preparations, or matter derived from organisms usually obtained by biological methods or assay. Biologic,Biologic Drug,Biologic Product,Biological,Biological Drug,Biological Medicine,Biological Product,Biologics,Biopharmaceutical,Natural Product,Natural Products,Biologic Drugs,Biologic Medicines,Biologic Pharmaceuticals,Biologic Products,Biological Drugs,Biological Medicines,Biologicals,Biopharmaceuticals,Products, Biological,Drug, Biologic,Drug, Biological,Drugs, Biologic,Drugs, Biological,Medicine, Biological,Medicines, Biologic,Medicines, Biological,Pharmaceuticals, Biologic,Product, Biologic,Product, Biological,Product, Natural
D012238 Rhodium A hard and rare metal of the platinum group, atomic number 45, atomic weight 102.905, symbol Rh. Rhodium-103,Rhodium 103

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