Abstract The Rh II-catalyzed cycloaddition cascade of an indolyl-substituted α-diazo imide was used for the total synthesis of the complex pentacyclic alkaloid (±)-aspidophytine. Treatment of the resulting dipolar cycloadduct with BF 3⋅ OEt 2 induces a domino fragmentation cascade. The reaction proceeds by an initial cleavage of the oxabicyclic ring and formation of a transient N-acyl iminium ion which reacts further with the adjacent tert- ...
