Xanthones and oxepino[2, 3-b]chromones from three endophytic fungi.
Three new metabolites, microsphaeropsones A-C (1-3) with a unique oxepino[2,3-b]chromen-6-one (ring-enlarged xanthone) skeleton, were isolated from the endophytic fungus Microsphaeropsis species, co-occurring with their putative biogenetic anthraquinoide precursors citreorosein (4) and emodin (5). From another Microsphaeropsis species, large amounts of fusidienol A (8 a), smaller amounts of emodin (5), the known aromatic xanthones 9 a and 9 b, the new 3,4-dihydrofusidienol A (8 b), and the new aromatic xanthone 9 c were isolated. The endophyte Seimatosporium species produced a new aromatic xanthone, seimatoxanthone A (10), and 3,4-dihydroglobosuxanthone A (12), closely related to alpha-diversolonic ester (13) from Microdiplodia sp.. The structures were determined mainly by extensive 1D and 2D NMR experiments and supported by X-ray single-crystal analysis of 1 and the oxidation product 7. The absolute configurations of the microsphaeropsones A-C (1-3) were established by comparison of the electronic and vibrational circular dichroism (ECD and VCD) spectra of 1 with time-dependent DFT (TDDFT) and DFT calculations by using either the solid-state structures or DFT-optimized geometries as inputs. Preliminary studies indicated that 1, 2, and enone 7 showed antibacterial, fungicidal, and algicidal properties.
Krohn
Karsten
K
Department Chemie, Universität Paderborn, Warburger Strasse 100, 33098 Paderborn, Germany. k.krohn@upb.de
Kouam
Simeon F
SF
Kuigoua
Guy M
GM
Hussain
Hidayat
H
Cludius-Brandt
Stephan
S
Flörke
Ulrich
U
Kurtán
Tibor
T
Pescitelli
Gennaro
G
Di Bari
Lorenzo
L
Draeger
Siegfried
S
Schulz
Barbara
B
D001419:Bacteria / Q000187:drug effects; D001688:Biological Products / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D002708:Chlorella / Q000187:drug effects; D002867:Chromones / Q000737:chemistry* / Q000302:isolation & purification* / Q000494:pharmacology; D002942:Circular Dichroism; D005658:Fungi / Q000737:chemistry*; D006865:Hydrogenation; D009682:Magnetic Resonance Spectroscopy; D010082:Oxepins / Q000737:chemistry*; D044004:Xanthones / Q000737:chemistry* / Q000302:isolation & purification* / Q000494:pharmacology
D001688:Biological Products; D002867:Chromones; D010082:Oxepins; D044004:Xanthones