Rifamycin S (1) was allowed to react with Na₂SO₃ under mild alkaline conditions to afford sodium rifamycin SV-3-sulfonate (3). Oxidation of 3 with MnO₂ gave sodium rifamycin S-3-sulfonate (4a). The reaction of 4a with aromatic amines and aliphatic secondary amines led to 3-aminorifamycin derivatives 5a-g. A novel cleavage reaction of the ansa-ring occurred to give compounds 7a-g, when 4a was allowed to react with aliphatic primary amines having at least one hydrogen atom at the α-position.