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

3-Hydroxyrifamycin S and further novel ansamycins from a recombinant strain R-21 of Nocardia mediterranei. Rifamycin Z, a novel ansamycin from a mutant of Nocardia mediterranea. Rifamycin G, a further product of Nocardia mediterranei metabolism. Isolation of 11,12-<i>seco</i>-Rifamycin W Derivatives Reveals a Cleavage Pattern of the Rifamycin <i>Ansa</i> Chain Biosynthetic origins of the oxygen atoms in the ansamycin antibiotics rifamycin B, O, and S Early intermediates in the biosynthesis of ansamycins. II. Isolation and identification of proasamycin B-M1 and protorifamycin I-M1. Juanlimycins A and B, Ansamycin Macrodilactams from <i>Streptomyces</i> sp. Juanlimycins A and B, Ansamycin Macrodilactams from <i>Streptomyces</i> sp. 31-Homorifamycin W, a novel metabolite from Amycolatopsis mediterranei. Isolation and structure of a new ansamycin antibiotic kanglemycin A from a Nocardia.