Biosynthetic relationships in the desertomycin family

Abstract

The minor metabolites oasomycin E, 8, and F, 9, isolated from the culture broth of Streptoverticillium baldacii subsp. netropse(strain FH-S 1625), were structurally characterized as new 42-membered macrolactones of the desertomycin family. A detailed analysis of the fermentation time-course of the producing organism, pH-static fermentations and in vitro conversions of the oasomycins result in a complete picture of the biosynthetic relationships of the desertomycin family. Desertomycin A, 1, the first product detected in the biosynthetic sequence, undergoes an oxidative deamination leading to oasomycin F, 9, which is converted via lactonization of the side chain into the main product oasomycin B, 5. In the late stage of the fermentation, enzymatic demannosylation resulted in the aglyca of the oasomycins 1, 8 and 7. In pH-static fermentations these results were successfully used to direct the fermentation process to produce the desired members of the desertomycin family.