Microbial transformation of isolongifolen-4-one

The microbial transformation of (+)-isolongifolen-4-one (4) by a number of fungi by means of a standard two-stage fermentation technique afforded (7R)-12-hydroxyisolongifolen-4-one (5), (7S)-13-hydroxyisolongifolen-4-one (6), (11R)-11-hydroxyisolongifolen-4-one (7), (10R)-10-hydroxyisolongifolen-4-one (8), and (9R)-9-hydroxyisolongifolen-4-one (9) (Scheme). All five metabolites were found to be new. and metabolites 6 and 9 showed potent tyrosinase inhibitory activity ( Table 1). The metabolites and their derivatives were characterized on the basis of spectroscopic and single-crystal X-ray-diffraction techniques.