Pigments of fungi. Part 11. (+)-Austrocorticin, austrocorticinic acid, austrocorticone, and related pigments; the first naturally occurring anthraquinones derived from a propionate-triggered octaketide

Abstract

The anthraquinones (7), (9), (11), (13), (15), and (17) have been isolated from the orange fruit bodies of an Australian toadstool belonging to the genus Dermocybe. Five of these six pigments bear a unique C₂ side chain at C-3 in the anthraquinone nucleus, the biogenetic origin of which has been studied by feeding ¹³C labelled precursors to young toadstools. High specific incorporation of isotope from sodium [3-¹³C]propionate into the C-3′ methyl group of pigments (7), (11), (13), (15), and (17) indicates that a propionate ‘starter’ effect is operating. The sixth pigment (9) is derived in the same organism by ‘normal’ acetate-triggered octaketide assembly.