Structures 1, 2 and 3 have been assigned to rifamycins P, Q and Verde, novel metabolites isolated from a mutant strain of Nocardia mediterranea both on the basis of spectroscopic evidence (UV, IR, MS, 1H and 13C NMR) in comparison with the model compounds rifamycin S (4), rifampicin (5) and 4-dimethylamino-4-deoxy-rifamycin SV (6), and of an unambiguous synthesis from rifamycin S (4).
