Biotransformation of digitoxigenin by Cochliobolus lunatus

The biotransformation of digitoxigenin (1) by Cochliobolus lunatus was investigated. The biotransformation reaction was carried out in a 4-day process, resulting in the isolation of four products, whose structures were elucidated as 1β-hydroxydigitoxigenin (2), 7β-hydroxydigitoxigenin (3), 8β-hydroxydigitoxigenin (4) and digitoxigenone (5). The production of these derivatives under the employed conditions has never been described so far. This is also the first report on the production of compound 4 by a biotransformation reaction. (author)