Hexacyclinic acid, a Polyketide fromStreptomyces with a Novel Carbon Skeleton

An unusual type I polyketide defined in a unique hexacyclic skeleton was determined as the structure of hexacyclinic acid (1). The structure was elucidated by X-ray analysis in connection with chemical–spectroscopic methods, and the biosynthesis was explored through feeding experiments with 13C-labeled precursors. The compound was isolated by application of the OSMAC approach to Streptomyces cellulosae S 1013.