Feeding experiments with 13C and 180-labeled precursors revealed that the molecular framework of the polycyclic xanthone antibiotics, the lysolipins X (1) and I (2), is derived from the polyketide pathway (12 malonate units), the Ci pool (methionine), molecular oxygen, and the nitrogen pool.Surprisingly, an intact malonate moiety serves as the three-carbon starter unit of the polyketide backbone, and 9 of the 12 oxygen atoms of 1 originate from molecular oxygen, including both of the xanthone oxygen atoms. The orientation of the malonate unit incorporated intact into lysolipin is unique and opposite from those in tetracycline and cycloheximide, i.e., the activated carbon of malonyl CoA is bound to the nitrogen of the lysolipin isoquinoline ring and the COa-derived carbon serves as the starter of the polyketide chain. From the biogenetic origin of the oxygen atoms several unusual prearomatic deoxygenation steps early in the biosynthesis have to be postulated.The polycyclic xanthone antibiotics form a small but distinct family of more than 20 members of microbial natural products. Their biological activities range from antibacterial (mainly Gram-positive bacteria including anaerobes,1-2 but also Gram-negative bacteria3), to anticoccidial,4 antifungal10•6 (e.g. yeasts, dermatophytes), and cytotoxic activities30•6 (e.g. HeLa cells).The lysolipins are antibacterial, antifungal (only 2), as well as cytotoxic compounds.3 After the albofungins,la~°t he lysolipins were the second group of the xanthone family of antibiotics to be discovered. These lipophilic antibiotics act lytically against cell walls, i.e., as inhibitors of cell wall biosynthesis (antagonism against lipid-bound mureine precursors).3® Lysolipin X (1) is the natural end product formed by Streptomyces violaceoniger (Tü 96) and the immediate precursor of lysolipin I (2), its dehydration product (Figure 1). While the absolute configuration of 2 could be established by X-ray analysis and chemical derivatization, the configuration of C-ll and C-12 in 1 is uncertain, because the instability of the molecule toward weak acids or light does not allow any chemical modificaf

An unexpected amino acid metabolism is used by a subspecies of the soil bacterium Streptomyces violaceoniger to produce the antifungal antibiotic pyridazomycin 1‐C1. Feeding studies with isotopically labeled precursors indicate that 1 is constructed from ornithine, glycine, and probably oxaloacetate.

Über einen unerwarteten Aminosäuremetabolismus produziert eine Subspezies des Bodenbakteriums Streptomyces violaceoniger das fungizide Antibioticum Pyridazomycin 1‐Cl. So ergaben Fütterungsversuche mit isotopenmarkierten Vorstufen, daß 1 aus Ornithin, Glycin und wahrscheinlich Oxalacetat aufgebaut wird.

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