Incubation of ent-19-hydroxy-13-epi-manoyl oxide with Gibberella fujikuroi afforded ent-12α,19-dihydroxy-13 -epi-manoyl oxide and ent-7β, 12α, 19-trihydroxy-13 -epi-manoyl oxide, the first of which was transformed by chemical methods into varol (ent-12α-hydroxy-13-epi-manoyl oxide). The incubation of ent-3β-hydroxy-13-epi-manoyl oxide (ribenol) with the same fungus gave the 12β-hydroxy, the 11β-hydroxy and the 11β,12β-dihydroxy derivatives of ribenol, the first of which was identical with varodiol. © 1989.
Fraga, B. M., González, pedro, Guillermo, R., Hernández, M. G., & Rovirosa, J. (1989). The microbiological transformation of some ent-13-epi-manoyl oxide diterpenes by Gibberella fujikuroi. Phytochemistry, 28(7), 1851–1854. https://doi.org/10.1016/S0031-9422(00)97873-7