Synthesis of febrifugine derivatives and a solution to the puzzle of the structural determination of febrifugine

The stereo-structure of piperidine lactone (), a synthetic intermediate of the antimalarial agent febrifugine ) with a piperidine ring in the trans relative configuration, was re-revised to the cis-form. We determined that isomerization to the trans-form from the cis-form occurred in the stage ( from ) of deprotection in Bakerʹs synthesis.