Ansamitocin libraries by combining mutasynthesis with chemical synthesis; A new version of total synthesis

Blocked mutants of Actinosynnema pretiosum, the producer of the highly cytotoxic antitumor agent ansamitocin, serve as powerful tools that allow synthetic chemists to generate natural product libraries. The power of this approach can be dramatically expanded when mutasynthesis is combined with chemical synthesis. This report provides illustrative examples of the application of this strategy to produce libraries based on the ansamycin antibiotics.