Biotransformation of a mulinane diterpenoid by Aspergillus alliaceus and Mucor circinelloides

The biotransformation of mulin-11,13-dien-20-oic acid (1), a diterpene isolated from extracts of Azorella compacta was evaluated using Aspergillus alliaceus UI 315 and Mucor circinelloides ATCC 7941. Cultures of A. alliaceus containing 1 produced the known metabolite 16-hydroxy-mulin-11,13-dien-20-oic acid (2) in 19.5% yield; alternatively, biotransformation of 1 by cultures of M. circinelloides produced two new metabolites identified as mulin-11,13-dien-16,20-dioic acid (3) and 7 alpha,13 beta-dihydroxy-mulin 11-en-20-oic acid (4) on the basis of their spectroscopic data.