Bioconversion of ascomycin and its 6-alkoxyderivatives

Abstract Ascomycin is known to be O -demethylated to 32- O -desmethyl-ascomycin by bioconversion using the strain Actinoplanes sp. ATCC 53771. Using modified screening media, the conversion rate could be improved from previously published 15% to up to 35%. Together with 32- O -desmethyl-ascomycin, two further metabolites, the already known 32- O -desmethyl-19-hydroxymethylascomycin and the new 32- O -desmethyl-32-epi-ascomycin were isolated and characterized. Prompted by the observed demethylation capability of ATCC 53771, we studied whether this strain was also able to dealkylate 6-alkoxy derivatives of ascomycin to 6-hydroxy-ascomycin. Although the 6-alkoxy derivatives were demethylated at various positions of the molecule, production of the hypothetical metabolite 6-hydroxy-ascomycin by biotransformation could not be shown. However, work up of the fermentation broth allowed the isolation and characterization of a new metabolite, the 6-ethoxy-15-desmethyl-ascomycin.