Total Syntheses of (−)-Deoxoapodine, (−)-Kopsifoline D, and (−)-Beninine

The total syntheses of Aspidosperma and Kopsia alkaloids (−)-deoxoapodine, (−)-kopsifoline
D, and (−)-beninine are described through a domino deprotection-Michael
addition-nucleophilic substitution protocol to assemble the core framework
in efficient steps. Corey–Bakshi–Shibata reduction was
employed to afford the enantioenriched intermediate for the total
syntheses of the aforementioned alkaloids. The chirality was shown
to completely transfer to the backbone using Johnson–Claisen
rearrangement. The enantioselective total syntheses of (−)-kopsifoline
D and (−)-beninine were accomplished for the first time. Our
strategy opens up practical avenues for the total synthesis of structurally
similar alkaloids.