AbstractThe 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.