STRUCTURE OF THE NEW SPIROKETAL-MACROLIDE A82548A

A new member of the spiroketal-containing macrolide class of fermentat ion-derived natural products was isolated from mycelial extracts of St reptomyces diastatochromogenes. The principal component, A82548A, was shown to possess a 22-membered macrolide ring system onto which was in corporated both a spiroketal and a hemiketal moiety. Relative stereoch emistry was established by single crystal X-ray diffraction studies. A bsolute stereochemistry was determined via hydrolysis of the amino sug ar glycosidically linked to the aglycone, which was identified as L-ke darosamine. The overall three-dimensional structure is closely related to that of the macrolides cytovaricin, rutamycin, and ossamycin.