Microbial conversion of ansamitocin.

Bacteria, actinomycetes, yeasts, and fungi were screened for their ability to modify the structure of ansamitocins, a group of antitumor ansamycin antibiotics. Many strains, mostly actinomycetes, were found to convert ansamitocin P-3 to one or more products. These products, compounds A, B, C, and D, were prepared using Bacillus megaterium IFO 12108, Streptomyces coelicolor IFO 3807, Streptomyces castaneus IFO 13670 and Streptomyces minutiscleroticus IFO 13361, and were identified as 20-O-demethylansamitocin P-3, maytansinol, 15-hydroxyansamitocin P-3 and N-demethylansamitocin P-3, respectively. Other maytansinoids also underwent these microbial conversions.