Two new gibberellins, A24 and A25, from Gibberella fujikuroi; their isolation, structure, and correlation with gibberellins A13 and A15

Abstract

The isolation is described of two new gibberellins from Gibberella fujikuroi—gibberellin A₂₄(IIa), the first fungal gibberellin with an aldehydic function, and gibberellin A₂₅(IIIa), the corresponding carboxylic acid. Their structures, deduced from spectroscopic data, were confirmed by correlation with gibberellin A₁₅(IVa), and by the partial synthesis of gibberellin A₂₅ trimethyl ester from gibberellin A₁₃. In the solid state gibberellin A₂₄ appears to exist in the lactol form (IVb), whereas in solution an equilibrium between the free aldehyde (IIa) and the lactol form (IVb) was detected by variable temperature n.m.r. studies.