Arenaric acid (Pa), a new pentacyclic polyether related to the antibiotics
K-41A and oxolonomycin, was isolated as its sodium salt (Ib) from the cultu
re broth of an estuarine bacterial isolate of the genus Streptomyces. The s
tructure of arenaric acid was established by spectroscopic methods involvin
g comprehensive 2D NMR measurements.