Stereoselective Synthesis of (−)-Desethyleburnamonine, (−)-Vindeburnol and (−)-3-epitacamonine: Observation of a Substrate Dependent Diastereoselectivity Reversal of an Aldol Reaction

Starting from (-)-acetoxyglutarimide, the enantioselective multistep synthesis of (-)-desethyleburnamonine, (-)-vindeburnol and (-)-3-epitacamonine has been demonstrated via a common hydroxyl-lactam intermediate with very good overall yields. The acetoxy function from (-)-acetoxyglutarimide was initially used as a handle to induce enantioselectivity and then as a latent source of the ketone carbonyl group. Most importantly, substrate dependent reversal of the diastereoselectivity in ester aldol reactions of hexahydroindolo[2,3-a] quinolizinones has been reported.