Pityriarubins, Biologically Active Bis(indolyl)spirans from Cultures of the Lipophilic Yeast Malassezia furfur

Indole alkaloids, such as pityriarubin A (1), may be of importance for the pathogenesis of the common skin disease pityriasis versicolor. The metabolite 1 is produced in cultures of the lipophilic yeast Malassezia furfur with tryptophan present as the sole source of nitrogen. The structures of the pityriarubins were derived from spectroscopic investigations, and insight into their biosynthesis was gained by feeding experiments with [1′‐13C]tryptophan.