Structures of the Metabolites from Steviol Methyl Ester by Gibberella fujikuroi

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Steviol methyl ester (methyl ent-13-hydroxykaur-16-en-19-oate)^* was converted into five new metabolites together with a known compound, methyl ent-7α, 13-dihydroxykaur-16-en-19-oate, by Gibberella fujikuroi in the presence of a plant growth retardant. The structures of these new metabolites were elucidated to be methyl ent-7β, 13-dihydroxykaur-16-en-19-oate, methyl ent-11α, 13-dihydroxykaur-16-en-19-oate, methyl ent-7β, 11α, 13-trihydroxykaur-16-en-19-oate, methyl ent-11α, 13, 15β-trihydroxykaur-16-en-19-oate and methyl ent-13, 15β-dihydroxy-11-oxokaur-16-en-19-oate mainly by spectroscopic analyses.