3-Hydroxyrifamycin S and further novel ansamycins from a recombinant strain R-21 of Nocardia mediterranei.

The structures of 3-hydroxyrifamycin S and six further novel ansamycins isolated from the recombinant strain R-21 of Nocardia mediterranei were identified by spectroscopic methods. Three types of structure were distinguished: Type 1: Ansamycins of the rifamycin S type Type 2: Ansamycins of the rifamycin G type Type 3: Ansamycins of the rifamycin W type.