Biotransformation of tetrahydro-alpha-santonins by Absidia coerulea.

The fungus, Absidia coerulea was employed to bioconvert tetrahydro-alpha-santonins, 1,2,4alpha,5alpha-tetrahydro-alpha-santonin (1), and its 4-epimer (2), from which 10 products (3-12) were obtained. Furthermore, their structures were determined, based on their chemical and spectroscopic data analyses. Among them, 3-5, 7, 9, 11 and 12 were observed to be seven new compounds. The reactions mainly involved in these bio-process included hydroxylation(s) (C-4, C-11, and C-1), reduction (C-3 ketone to alcohol).