Protecting-Group-Free Total Synthesis of Anticancer (±)-Melotenine A

Abstract Melotenine A, isolated from Melodinus tenuicaudatus, possesses significant anticancer activity against several human cancer cell lines. The synthesis of (±)-melotenine A was achieved without the use of any protecting groups in 11 steps with an overall yield of 6.7%. The key steps of our strategy were a Diels–Alder reaction to construct the tetracyclic framework and ring-closing metathesis to form the seven-membered ring of (±)-melotenine A.