Fungal products. Part XVII. Microbiological hydroxylation of gibberellin A9 and its methyl ester

Abstract

Gibberellin A₉(1) is metabolised by re-suspended cultures of Gibberella fujikuroi, mutant B1-41a, principally to gibberellins A₂₀(17) and A₄₀(18). Other metabolites, detected by g.l.c.–mass spectrometry include gibberellin A₁₀(2) and A₁₁(24); two didehydrogibberellin A₉ derivatives (12) and (14); 16α,17-dihydro-16,17-dihydroxy-gibberellin A₉(26); 3-epi-gibberellin A₄(4); and a monohydroxygibberellin A₉, possibly (19). Gibberellin A₉ is partially metabolised by cultures of Rhizopus nigricans to give only gibberellin A₁₀(2). Gibberellin A₉ methyl ester, however, is converted into the methyl esters of the 16α- and 16β-epimers (26) and (27) of 16,17-dihydro-16,17-dihydroxygibberellin A₉, gibberellin A₂₀(17), gibberellin A₄₀(18), gibberellin A₄₅(20), and a monohydroxygibberellin A₉, possibly (19).