Isolation of 11,12-seco-Rifamycin W Derivatives Reveals a Cleavage Pattern of the Rifamycin Ansa Chain

This study reported the isolation and characterization of 11 rifamycin congeners including six new ones (1–6) from the agar fermentation extract of Amycolatopsis mediterranei S699. Compounds 1 and 2 are rifamycin glycosides named as rifamycinosides A and B, respectively. Their polyketide skeleton represents a novel cleavage pattern of the rifamycin ansa chain. Compounds 6 and 8 showed potential T3SS inhibitory activity, and 6 induced G2/M phase arrest and caused DNA damage in HCT116 cells.