Oxidative biotransformation of stemofoline alkaloids.

Biotransformations of stemofoline (), (2')-hydroxystemofoline (), (11)-1',2'-didehydrostemofoline () and stemocurtisine () were studied through fermentation with TISTR 3370. Three new stemofoline derivatives; 6 -hydroxystemofoline (), (2', 6 )-dihydroxystemofoline () and (11,6)-1',2'-didehydro-6-hydroxystemofoline (), together with the known compound 1',2'-didehydrostemofoline--oxide (), were produced by C-hydroxylation and N-oxidation reactions. Stemocurtisine was not biotransformed under these conditions. The transformed product was four times more potent (IC = 11.01 ± 1.49 µM) than its precursor (IC = 45.1 ± 5.46 µM) as an inhibitor against acetylcholinesterase.