ansamycin

noun

an·​sa·​my·​cin ˌan-sə-ˈmī-sᵊn 

: any of several antibiotics (such as the rifamycins and streptovaricins) that are derived from actinomycetes and share a chemical structure in which nonadjacent positions on an aromatic ring are connected by an aliphatic chain

The structural complexity of rifamycin and other ansamycins has made biosynthetic manipulation an attractive route for the generation of pharmacologically useful analogs.

—Kenji Watanabe et al., Proceedings of the National Academy of Sciences