Transformation of rifamycin S into rifamycins B and L. A revision of the current biosynthetic hypothesis.

The transformation of rifamycin S into rifamycins B and L was reinvestigated in order to establish more detailed pathways. Our results exclude rifamycin O as a common progenitor in the biosyntheses of rifamycins B and L. Rifamycins B and L are formed from rifamycin S (SV) by different pathways using different C3-precursors for the biosynthesis of their glycolic acid moieties. A thiamine-dependent enzyme (decarboxylase) seems to be involved in the transformation reaction.