Thiazo rifamycins—I

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, 1 H and 13 C 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 ).