Some recent studies on the metabolites of fungi and lichens

Various anthraquinonoid colouring matters grouped into (a) monomeric anthraquinones, (b) bianthraquinones and (c) modified bianthraquinones were isolated from Pen icillium islandicum, P. rugulosum, and other fungi. The unusual cagelike structures of hepatotoxic luteoskyrin, (—)rubroskyrin, (+)rugulosin and their analogues are elucidated. The absolute stereochemical structures of these fungal colouring matters have been established on the basis of the x-ray crystallographical analysis of a bromination product of (+)tetra-hydrorugulosin. The photoreaction of (—)luteoskyrin is discussed in elucidat-irig the structure of the product, lumiluteoskyrin. In addition, (—)flavoskyrin, isolated from a strain of Penicillium islandicurn, has now been proved to be a modified bianthraquinone. An unusual dimerization reaction of the dihydro-anthraquinones which were synthesized as model compounds for flavoskyrin is also discussed. (+)Rugulosin, skyrin, some fungal modified bixanthones and their related compounds have recently been found in certain lichens. The