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Keywords:

  • antibiotics;
  • biosynthesis;
  • drug discovery;
  • natural products;
  • spiro compounds;
  • structure elucidation

Abstract

In an antibiotic lead discovery program, the known strain Streptomyces armeniacus DSM19369 has been found to produce three new natural products when cultivated on a malt-containing medium. The challenging structural elucidation of the isolated compounds was achieved by using three independent methods, that is, chemical degradation followed by NMR spectroscopy, a computer-assisted structure prediction algorithm, and X-ray crystallography. The compounds, named armeniaspirol A–C (24), exhibit a compact, hitherto unprecedented chlorinated spiro[4.4]non-8-ene scaffold. Labeling experiments with [1-13C] acetate, [1,2-13C2] acetate, and [U-13C] proline suggest a biosynthesis through a rare two-chain mechanism. Armeniaspirols displayed moderate to high in vitro activities against Gram-positive pathogens such as methicillin-resistant S. aureus (MRSA) or vancomycin resistant E. faecium (VRE). As analogue 2 was active in vivo in an MRSA sepsis model, and showed no development of resistance in a serial passaging experiment, it represents a new antibiotic lead structure.