Hydroxylation of the diterpenes ent-kaur-16-en-19-oic and ent-beyer-15-en-19-oic acids by the fungus Aspergillus niger

Incubations of the fungus Aspergillus niger with ent-kaurenoic (1) afforded the spasmolytic metabolites 4 and 5, while incubation with 2 yielded metabolite 6 in high yield (40%).