Microbial Transformation of (+)- and (−)-2′-Demethoxydehydro-griseofulvin by Streptomyces cinereocrocatus

To elucidate the microbial activities of Streptomyces cinereocrocatus, (+)- and (—)-2′- demethoxydehydrogriseofulvin (1c and 3c) were synthesized and subjected to microbial transformation. The microbial transformation of the (—)-enantiomer (3c) afforded (+)-2′-demethoxy-2′,3′-dihydrodehydrogriseofulvin (18) as the sole product in a high yield (60%). On the other hand, the microbial transformation of the (+)-enantiomer (1c) gave (+)-2′-demethoxygriseofulvin (6) (12%) and a mixture of (—)- and (+)-2′-demethoxy-2′,3′-dihydrodehydrogriseofulvin (14 and 18) (8%). The results indicate that the microbial transformations take place directly and/or after isomerization with hydrogenations, depending on the kinds of substrates concerned, i.e., (+)- and (—)-2′-demethoxydehydrogriseofulvin analogs. It was concluded that the modes of microbial transformation of dehydrogriseofulvin analogs are greatly influenced by the structure of the substrates, i.e. the substituent at the 2’-position and/or the enantiomeric nature.