Extension of the erythromycin biosynthetic pathway

Erythromycin A is slowly metabolized to a new antibiotic, erythromycin E (5), when incubated with fermentations of certain strains of the producing organism Streptomyces erythreus. Erythromycin E contains a novel ortho ester grouping not previously encountered in macrolide antibiotics. The isolation of erythromycin E extends and further delineates the latter stages of the erythromycin biogenetic pathway.