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

The microbiological transformation of 7-oxo-ent-kaur-16-ene by the fungus Gibberella fujikuroi gave fujenoic acid as the main compound, whilst the incubation of 18-hydroxy-7-oxo-ent-kaur-16-ene and 3 alpha,18-dihydroxy-7-oxo-ent-kaur-16-ene afforded the corresponding 6 beta-hydroxy-derivatives. These facts indicate that the formation of fujenoic acid in this biotransformation should occur via a 7-oxo-6 beta-hydroxy derivative. In the three biotransformations. an 11 beta-hydroxylation was also produced. in low yield, indicating that a 7-oxo-group also directs hydroxylation at C-11. (c) 2005 Elsevier Ltd. All rights reserved.