The biogenesis of rifamycin S

Propionic acids labelled either with ¹⁴C in positions 1, 2, or 3, or with ¹⁴C in position 1 and ³H in position 3 have been used as precursors in biosynthesis of rifamycins by Streptomyces mediterranei. The resulting distribution of radioactivity in rifamycins S – as determined by systematic degradation – shows that 23 of the 37 carbon atoms in rifamycin S originate from propionic acid. This result and the distribution pattern of radioactivity are in agreement with those obtained recently by ¹³C-NMR. spectroscopy 7]. The S-methyl groups of methionin, labelled with ¹⁴C, are incorporated in rifamycins by Streptomyces mediterranei only in the methoxy group. The consequences of these findings for the biogenesis of other ansamycins, e.g. streptovaricins, are discussed. The similarities in the constitution and configuration of ansamycins and macrolides (cf. 9]) indicate that all these microbial metabolites are formed according to the same biogenetic pattern.