Asymmetric Synthesis of the Indolo[2,3‐α]quinolizine Alkaloid (+)‐Cuscutamine via a Diastereoselective Intramolecular Pictet‐Spengler Reaction

Abstract A concise total synthesis of Cuscutamine was achieved involving a diastereoselective intramolecular acyl iminium ion mediated Pictet‐Spengler reaction. This synthetic strategy provided a direct route to (11 S , 13 R )‐Cuscutamine ( 2 ) in only 3 steps with an overall yield of 56 % and an enantiomeric ratio of 88 %. The diastereoselectivity of the reaction is consistent with previous studies that proceed via more highly puckered …