Biotransformation of methyl ent-17-hydroxy-16beta-kauran-19-oate by Rhizopus stolonifer.

Methyl ent-17-hydroxy-16beta-kauran-19-oate was fed to a 2-day-old culture of the fungus Rhizopus stolonifer, fermenting at room temperature (25 degrees C) in an orbital shaker (21). After 11 days, both broth and mycelia were extracted with ethyl acetate. Two novel compounds were isolated from this experiment: methyl ent-9alpha,17-dihydroxy-16beta-kauran-19-oate and methyl ent-7alpha,17-dihydroxy-16beta-kauran-19-oate. Their structures were fully confirmed by spectroscopic methods.