Myrtoidine and malagashanine, highly complex in dole alkaloids, are effective adjuvants in developing cures for plasmodium malaria and potent multi-drug resistant agents. Despite nearly 30 years of progress, myrtoidine and the related family of Malagasy alkaloids still present formidable challenges for synthetic chemists. Here, we developed a diastereoselective [2+2+2] tandem cyclization reaction with alkyl-substituted methylene malonate, enabling highly efficient collective total synthesis of four Malagasy alkaloids from commercially available tryptamines within 10-13 steps. The synthetic strategy included rapid and highly stereoselective assembly of the tetracyclic indoline core containing 5-7 contiguous stereogenic carbon centers, rarely seen in indole alkaloids. Among the four natural products, (+/-)-myrtoidine, (+/-)-11-demethoxymyrtoidine, and (+/-)-12-hydroxymalagashanine were synthesized for the first time, and the work on (+/-)-malagashanine represented the shortest synthetic route so far. Our current study should enable further explorations of chemical and biological spaces based on myrtoidine, malagashanine, and related natural products.