Abstract

The rifamycins are antibiotics derived from Streptomyces mediterranei.¹ Their chemical structure is novel, with a long aliphatic bridge spanning an aromatic system. They act by inhibiting bacterial RNA polymerase, as do the actinomycins. Of the five compounds originally isolated, only rifamycin B was obtained in stable crystalline form, and three substances derived from this have come into clinical use: rifamycin SV, ² rifampicin,³ and rifamycin B-diethylamide or rifamide (Rifocin-M - Lepetit).⁴