Studies in terpenoid biosynthesis. Part IX. The sequence of oxidation on ring B in kaurene–gibberellin biosynthesis
The formation of 7β-hydroxy-(–)-kaur-16-en-19-oic acid and its incorporation into gibberellic acid and the kauranoid metabolites of Gibberella fujikuroi are described. The results of incubation of 7β-hydroxy-[6β-3H,17-14C]-(–)-kaur-16-en-19-oic acid have shown that the 6β-hydrogen atom is lost in the formation of gibberellic acid. However 6β,7β-dihydroxy-(–)-kaur-16-en-19-oic acid is not incorporated into gibberellic acid. Experiments with [1-3H2,1-14C]geranyl pyrophosphate suggest that the 6β-hydrogen atom migrates to C-7 during ring contraction.