Two new macrolides produced by Streptomyces sp. CS.

A strong antifungal and antitumor agent, 24-demethylbafilomycin C1 (1) has been isolated from Streptomyces sp. CS1). The structure of 1 is different from those of bafilomycins at the replacement of the isopropyl group with ethyl group at C-23, and different from hygrolidins at C-2 substitution and the orientations of the substituents at C-21, C-22 and C-23 in the pyranose ring2-5). Therefore it belongs to a new subfamily of 16-membered macrolides. The isolation of 1 from this strain in previous work encouraged us to search for this type of metabolites further, which led to the isolation of compound 1 and two new bafilomycin derivatives 2 and 3. Their structures were elucidated based on the NMR experiments.