Total Synthesis of Longeracinphyllin A

The first and asymmetric total synthesis
of longeracinphyllin A,
a hexacyclic Daphniphyllum alkaloid, has been accomplished.
A tetracyclic intermediate was prepared through silver-catalyzed alkyne
cyclization and Luche radical cyclization. A phosphine-promoted [3
+ 2] cycloaddition reaction was exploited to construct the sterically
congested E ring bearing vicinal tertiary and quaternary centers.
The cyclopentenone motif was assembled by using intramolecular Horner–Wadsworth–Emmons
olefination. Raney Ni reduction delivered the tertiary amine from
a thioamide precursor at a late stage.