title: Cohaerins G-K, azaphilone pigments from Annulohypoxylon cohaerens and absolute stereochemistry of cohaerins C-K.
abstract: Four azaphilones, for which the trivial names cohaerins G, H, I and K are proposed, were isolated from the methanolic stromatal extract of Annulohypoxylon cohaerens together with the known metabolites cohaerins C-F and 4,5,4',5'-tetrahydroxy-1,1'-binaphthyl (BNT). Their planar structures were determined by NMR spectroscopy and by mass spectrometry. While their core structure is identical with cohaerin C and F, respectively, subgroups 2-hydroxy-6-methylphenyl and (1R,2R,4S)-4-hydroxy-2-methyl-6-oxocyclohexyl account for the structural diversity as substituents at C-3 of the azaphilone core. The absolute stereochemistry was assigned by NOE NMR experiments, CD spectroscopy and derivatisation with Mosher's acid; in addition, the stereochemistry of cohaerins C-F was revised. The metabolites showed cytotoxic effects besides a weak antimicrobial activity.
authors: Helmholtz Centre for Infection Research GmbH, Department Microbial Drugs, Inhoffenstraße 7, 38124 Braunschweig, Germany.
authors: Frank
authors: F
authors: Surup
authors: Kathrin I
authors: KI
authors: Mohr
authors: Rolf
authors: R
authors: Jansen
authors: Marc
authors: M
authors: Stadler
mesh_terms: D000890:Anti-Infective Agents / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D001203:Ascomycota / Q000737:chemistry*; D001578:Benzopyrans / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology; D001688:Biological Products / Q000737:chemistry* / Q000494:pharmacology; D015394:Molecular Structure; D010860:Pigments, Biological / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology
chemical_list: D000890:Anti-Infective Agents; D001578:Benzopyrans; D001688:Biological Products; D010860:Pigments, Biological; C494154:azaphilone
keywords: Annulohypoxylon cohaerens; Azaphilone; Chemotaxonomy; Cohaerin; Natural products; Secondary metabolites; Structure elucidation; Xylariaceae