FIG. 6.
Proposed pathway for the biosynthesis of the 4-propenyl-2,3-dihydropyrrole-2-carboxylic acid moiety in sibiromycin, which is the suggested substrate for the NRPS enzymes catalyzing diazepine ring formation. The branching points for the anthramycin, tomaymycin, and lincomycin A biosyntheses are indicated.