A New Strategy for the Total Synthesis of Pentacyclic Tubifolidine

In a one-step reaction, we introduce that novel synthetic routes of a tetrahydrozarbazole derivative bearing a caboxylmethylene side chain exist at the C-2 position. Upon treatment with DDQ, it undergoes the cyclization reaction of amide (6) for the synthesis of methanoazocino[4,3-b]indole. Furthermore, the reduction of compound 9 with LiALH₄ in refluxing THF-furnished tubifolidine 10 via an eight-step synthetic sequence, which involves the synthesis of compound 3 in one step, is the crucial step. The structures of all currently synthesized compounds were confirmed using spectroscopic techniques (¹H NMR, ¹³C NMR, FT-IR).