Hydroxylation of yohimbine in superacidic media: One-step access to human metabolites 10 and 11-hydroxyyohimbine

Two major human metabolites of yohimbine (1), 10- and 11-hydroxyyohimbine ( 2 and 3), were prepared by direct hydroxylation of 1 under superacidic cond itions. In this medium, the four positions of the benzene part of yohimbine were hydroxylated and the corresponding monohydroxylated compounds (2-5) w ere isolated. The structures of 2-5 were elucidated by spectroscopic method s including 1D and 2D NMR techniques.