Balmoralmycin, a new angucyclinone, and two related biosynthetic shunt products containing a novel ring system.

A new angucyclinone, named balmoralmycin (1), was isolated as an inhibitor of protein kinase C-alpha (PKC-alpha) from the Streptomyces strain P6417. Chemical screening of extracts of the same strain resulted in the detection of two decaketides with unusual structural features (2 and 3). Both compounds belong to a recently described structural class of secondary metabolites which arises from engineered biosynthesis of a recombinant Streptomyces strain. The isolation of compounds of this class from a wild-type strain has never been reported before.