Biosynthetic origins of the polycyclic xanthone antibiotic, citreamicin

The biosynthesis of citreamicin 1 has been studied by feeding 13C- and 18O-labelled precursors to Micromonospora citrea cultures. 13C-NMR spectroscopic analysis of the enriched products demonstrated a labelling pattern indicating that the antibiotic is derived from a polyketide which undergoes rearrangement by a mechanism unique for xanthone biosynthesis.