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.