Synthesis of 18R-hydroxy-epiallo-yohimbines from (−)-3-iso-19,20-dehydro-β-yohimbine: an enantiospecific route to deserpidine and reserpine analogues from secologanin

(−)-3-Iso-19,20-dehydro-β-yohimbine has been converted into epiallo-yohimbines and, via a novel regio- and stereoselective hydration, into the 18R-hydroxy derivative, an analogue of deserpidine. Its 11-methoxy derivative, also prepared from secologanin, is a potential precursor for a reserpine analogue.