Streptomyces hygroscopicus is a natural producer of geldanamycin. Mutasynthetic supplementation of an AHBA-blocked mutant with all possible monofluoro 3-aminobenzoic acids provided new fluorogeldanamycins. These showed strong antiproliferative activity and inhibitory effects on human heat shock protein Hsp90. Binding to Hsp90 in the low nanomolar range was determined from molecular modelling, AFM analysis and by calorimetric studies.

Supplementing an AHBA(-) mutant strain of Amycolatopsis mediterranei, the rifamycin producer, with a series of benzoic acid derivatives yielded new tetraketides containing different phenyl groups. These mutasynthetic studies revealed unique reductive properties of A. mediterranei towards nitro- and azidoarenes, leading to the corresponding anilines. In selected cases, the yields of mutaproducts (fermentation products isolated after feeding bacteria with chemically prepared analogs of natural building blocks) obtained are in a range (up to 118 mg L(-1)) that renders them useful as chiral building blocks for further synthetic endeavors. The configuration of the stereogenic centers at C6 and C7 was determined to be 6R,7S for one representative tetraketide. Importantly, processing beyond the tetraketide stage is not always blocked when the formation of the bicyclic naphthalene precursor cannot occur. This was proven by formation of a bromo undecaketide, an observation that has implications regarding the evolutionary development of rifamycin biosynthesis.

The diastereoselective synthesis of (+)‐6,7‐dimethoxy‐1,2,3,4‐tetrahydroisoquinoline‐1‐carboxylic acid (90 % ee) was accomplished by employing a combination of two synthetic methods, that is, the Petasis synthesis of amino acids and the Pomeranz–Fritsch–Bobbitt synthesis of tetrahydroisoquinoline derivatives. The stereochemical outcome of the synthesis was controlled by chiral aminoacetaldehyde acetals, which were used as the amine component of the Petasis step to yield the Pomeranz–Fritsch–Bobbitt substrate for the tetrahydroisoquinoline ring formation in one simple operation.