Chem. Pharm. Bull. 53(2) 256—257 (2005)

Mastigophorenes A—D (1—4) are dimeric herbertenetype sesquiterpenoids found only in the liverwort Mastigophora diclados (BRID.) NEES. They have usually been isolated with their precursor herbertenediol (5). Our recent investigation of a liverwort sample collected from Madagascar, however, did not show any trace of mastigophorenes A and B but revealed the presence of 3—5. The remarkable neurotrophic activity of mastigophorenes A, B, and D has attracted considerable attention from synthetic chemists. The synthesis of these compounds was started by Bringmann and coworkers who used biomimetic oxidative dimerization of the protected monomeric precursor and atropoenantioselective synthesis via lactone methodology. Fukuyama et al. used the same method to obtain a large amount of sample for biological evaluation. Even though no experimental evidence has been reported, it was obvious that the biosynthesis of 1 and 2 was from the oxidative phenolic coupling of ( )-herbertenediol. To obtain structurally interesting and biologically active compounds and to evaluate the mechanism of introducing an oxygen functional group at a nonactivated carbon atom in organic compounds, biotransformation of secondary metabolites is a topic of systematic investigations in our laboratory. Carbon–carbon bond formation from the biotransformation of organic compounds is not common. Moreover, biotransformation using microorganism could give information on the enzymes involved in sesquiterpene biosynthesis. The present communication deals with the bioconversion of herbertenediol (5) into 1 and 2 by Penicillium sclerotiorum.