Isolation of dimeric nonactic acid from the nonactin-producing Streptomyces spec. JA 5909-1

The formation of possible intermediates of nonactin (I) biosynthesis by Streptomyces spec. JA 5909-1 was investigated. In addition to monomer nonactic acid (II), the dimeric nonactic acid (III) was isolated suggesting that III could be an intermediate of nonactin biosynthesis. The structure of III was settled by electrospray mass-spectrometry and high-field FT-NMR methods. III displays no antibacterial and antifungal activities supporting the view that cation complex formation by nactin-type antibiotics requires the entire macrotetrolide ring.