Isolation and characterization of the first halogen containing polyether antibiotic X-14766A, a product of Streptomyces malachitofuscus subsp. downeyi.

This report describes the isolation and chemical characterization of antibiotic X-14766A, the first halogen containing polyether antibiotic, from fermented cultures of Streptomyces malachitofuscus subsp. downeyi. The structure of this novel antibiotic was determined by X-ray analyses of the thallium and rubidium salts. In addition to the chlorine atom, which is attached to a salicylic acid chromophore, the molecule contains a tricyclic di-spiroketal ring system and an ethyl ester group.