3-Amino-5-hydroxybenzoic acid in antibiotic biosynthesis VI. Directed biosynthesis studies with ansamycin antibiotics.

Biosynthesis of the ansamycin antibiotic actamycin (2) was markedly increased by the addition of the precursor 3-amino-5-hydroxybenzoic acid (1) to the producing Streptomyces fermentation. Similar addition of the 4-chloro, 6-chloro, N-methyl and O-methyl analogues 4, 6, 5 and 7 of the amino acid 1 reduced actamycin production and did not yield structurally modified ansamycins. These results with the analogues 4, 5 and 7 indicate that the corresponding chlorine, N-methyl and O-methyl substituents present in the nuclei of various ansamycins are introduced at biosynthetic stages beyond the level of the amino acid 1.