Esperamicin P, the tetrasulfide analog of esperamicin A1.

A minor congener of esperamicin A1 [1], designated esperamicin P (BMY-41339, 2), was isolated from a fermentation broth of Actinomadura verrucosospora and determined to differ from esperamicin A1 by having a methyl tetrasulfide moiety instead of a methyl trisulfide. It was active against xenografted tumors in mice and exhibited antimicrobial activity. Interconversions of 2 and 1 have been observed for DMSO solutions of both congeners at room temperature.