Pigments of fungi. Part 12. Structure and absolute stereochemistry of antibiotic tetrahydroanthraquinones from the fungus Dermocybe splendida Horak. X-Ray structure determination of austrocortirubin phenylboronate and austrocortilutein acetonide

(1S,3S)-(+)-Austrocortirubin (6), (1S,3S)-(+)-austrocortilutein (8) and (1S,3R)-(+)- austrocortilutein (10) have been isolated from fresh fruit bodies of the fungus Dermocybe splendida and their structures established by chemical, spectroscopic, and X-ray crystallographic methods. Absolute stereochemistry has been established by chemical correlation with (2R)-methyl 2-(2′-methyl-5′-oxotetrahydrofuryl)acetate (27) and confirmed by single crystal X-ray analysis of the acetonide derivative (23) of (1S,3S)-austrocortilutein. The tetrahydroanthraquinones (6), (8) and (10) are active at low concentration against a range of bacteria and fungi.