ISOLATION OF DIMERIC NONACTIC ACID FROM THE NONACTIN-PRODUCING STREPTOMYCES SPEC JA-5909-1

The formation of possible intermediates of nonactin (I) biosynthesis b y Streptomyces spec. JA 5909-1 was investigated. In addition to monome r nonactic acid (II), the dimeric nonactic acid (III) was isolated sug gesting that III could be an intermediate of nonactin biosynthesis. Th e structure of III was settled by electrospray mass-spectrometry and h igh-field FT-NMR methods. III displays no antibacterial and antifungal activities supporting the view that cation complex formation by nacti n-type antibiotics requires the entire macrotetrolide ring.