Terpenoids produced by actinomycetes:: Napyradiomycins from Streptomyces antimycoticus NT17

Napyradiomycin SR (1), 16-dechloro-16-hydroxynapyradiomycin C2 (2), 18-hydroxynapyradiomycin Al (3), 18-oxonapyradiomycin Al (4), 16-oxonapyradiomycin A2 (5), 7-demethyl SF2415A3 (6), 7-demethyl A80915B (7), and (R)-3-chloro-6-hydroxy-8-methoxy-alpha-lapachone (8) were isolated from the culture broth of Streptomyces antimycoticus NT17. These compounds are derivatives of the napyradiomycins isolated previously from Chainia rubra or Streptomyces aculeolatus. The structures of the new compounds, some of which exhibit antibacterial activities, were established by comparing their NMR data with data of related known compounds. The unique structure of 1, containing a highly strained ring, was established by NMR and was confirmed by X-ray analysis. Two of the compounds are C-16 stereoisomers of napyradiomycin A2 and are named napyradiomycins A2a (9a) and A2b (9b).