Preparation of 13-hydroxygibberellin A12-7-aldehyde

Abstract

7β and 7α-Hydroxykaurenolides have been efficiently 13-hydroxylated by cultures of Rhizopus arrhizus. The products have been chemically converted into the title compound. In an alternative prepation, gibberellin A₁₂-7-aldehyde, [18-²H]gibberellin A₁₂-7-aldehyde (prepared from 7β, 18-dihydroxy-kaurenolide), and [6-³H]gibberellin A₁₂-7-aldehyde (prepared, by hydrogen–tritium exchange, from gibberellin A₁₂-7-aldehyde), have been 13-hydroxylated by cultures of Rhizopus arrhizus to give the unlabelled and the [18-²H]-and [6-³H]-labelled title compound. 13-Hydroxylation of gibberellin A₁₂-7-alcohol by cultures of Rhizopus arrhizus, followed by oxidation, also gave 13-hydroxygibberellin A₁₂-7-aldehyde.