Synthesis of [2H]gibberellins from steviol using the fungus Gibberella fujikuroi

²H]Steviol (ent-13-hydroxykaur-16-en-19-oic acid) was synthesized from steviol acetate norketone (ent-13-acetoxy-16-oxo-17-norkauran-19-oic acid) by the Wittig reaction using (methyl-d₃)triphenylphosphonium bromide. A mixture of steviol analogs was produced containing from one to four ²H/molecule. ²H]Steviol was fed to strain LM-45-399 of the fungus Gibberella fujikuroi which was grown on synthetic medium (ICI, 0% N) in the presence of the growth retardant CCC. ²H]GA₁, ²H]GA₁₈, ²H]GA₂₃ and ²H]GA₅₃ were isolated from the fungal medium after 4 days. This strain converted steviol to 13-hydroxy GAs in the highest yields of the four Gibberella strains tested, and in amounts suitable for metabolic studies with higher plants.