Biotransformation of 7-oxo-ent-kaur-16-ene derivatives by Gibberella fujikuroi

The microbiological transformation of 7-oxo-ent-kaur-16-ene by Gibberella fujikuroi gave fujenoic acid (27) as the main compound, whilst the incubation of 18-hydroxy-7-oxo-ent-kaur-16-ene and 3α,18-dihydroxy-7-oxo-ent-kaur-16-ene afforded the corresponding 6β-hydroxy derivatives. These facts indicated that the formation of fujenoic acid in this biotransformation should occur via a 7-oxo-6β-hydroxy derivative.