Our next attempt was the construction of the pentacyclic compound 12. The development of an inexpensive and scalable method for the preparation of vobasinol skeleton 2 is one of the most important aspects of this synthetic route. Several synthetic approaches for vobasinol scaffold 2 have been reported. However, some of them require expensive Pd catalysts, which have dramatically increased in recent years, and are not suitable for the decagram scale, or require activation of the ketone moiety of the starting material, or several derivatization steps after the cyclization reaction. In view of this, we investigated various cyclization reactions of 9. Interestingly, 12 was found to be easily synthesized by the reaction of 9 with Mn(OAc)3 at room temperature in acetic acid (49%, E/Z = 1:1). The reaction mechanism involves the coordination of 9 to Mn(OAc)3 to form the Mn-enolate 10. Subsequently, 10 undergoes enolate oxidation to form 11, which has a radical at the α-position of the ketone. Then 11 is subjected to a radical addition with a nearby alkyne to form 12-Z and 12-E. This concise and short-step strategy has made it possible to prepare pentacyclic compound 12, a common intermediate for many vobasine alkaloids, from inexpensive tryptophan on a decagram scale in only 6 steps. Notably, 12-Z and 12-E are separable and can be derivatized to related natural products. The obtained 12-Z with Boc group was deprotected to achieve a simple formal synthesis of koumidine with antitumor activity (see Supporting Information). 10 On the other hand, 12-E was converted to 13 by the Wittig reaction. The resulting 13 was hydrolyzed to the aldehyde with trifluoroacetic acid, and the thermodynamically stable stereochemistry of the methyl ester 14 was obtained using iodine, KOH, and MeOH, followed by Boc protection.