alpha-hydroxylabd-13(16),14-dien-18-oate with m-chloroperbenzoic acid gave methyl (13S)-ent-16-hydroxy-8 alpha,13-epoxylabd-14-en-18-oate and its epimer at C-13. Biotransformation of the former (which exhibits antileishmania activity) with Rhizopusnigricans cultures produced the methyl (13S)-ent-11 beta,16-dihydroxy-8 alpha,13-epoxilabd-14-en-18-oate (carbomanoyl, which inhibits the activity of the adenylatecyclase