Functionalization of β-carbolines is a challenge as numerous natural alkaloids with different biological activities present this heterocycle. The RCM is used herein with allyl-, vinyl-, ethynyl-, and propargyl-β-carbolines to generate additionally fused hetero-and carbocycles, and it is combined with other cyclization processes to achieve great molecular complexity in one synthetic step. Thus, an RCM–Diels–Alder sequence gives pentacyclic compounds ...