Fungal products. Part 20. Transformations of 2- and 3-hydroxylated kaurenoids by Gibberella fujikuroi

Abstract

ent-3α-Hydroxy- and ent-2α,3α-dihydroxy-kaur-16-en-19-oic acids have been prepared from ent-kaur-16-ene-3β,19-diol, and their metabolites from cultures of the mutant B1-41a of Gibberella fujikuroi have been analysed by g.l.c.–mass spectrometry. The metabolism of ent-2α-hydroxy, ent-2β-hydroxy-, and ent-3α-hydroxykaur-16-en-19-ols has been similarly investigated in cultures of the parent wild-type strain, GF-1a, in which gibberellin biosynthesis was blocked by a synthetic plant growth retardant. The results show that the ent-3α-hydroxylated analogues of the normal gibberellin intermediates, ent-kaur-16-en-19-ol and ent-kaur-16-en-19-oic acid, are efficiently converted into 3-hydroxylated gibberellins. They also indicate that the ent-2β-hydroxy-analogue is converted into gibberellin A₃ by dehydration and that the conversion of ent-kaurenoids into gibbereilins is reduced by the presence of ent-2α- and ent-2β-hydroxy-groups.