We report the first total synthesis of (–)-kopsifoline A and (+)-kopsifoline E. Our synthetic strategy features a biogenetically inspired regioselective C17-functionalization of a versatile intermediate containing the pentacyclic core of aspidosperma alkaloids. While this advance intermediate provides (–)-kopsifoline D via C3–C21 bond formation, regioselective C17-boronation of its indoline substructure prior to introduction of the F-ring enables access to (–)-kopsifoline A and (+)-kopsifoline E. The vinylogous urethane substructure of the key intermediate was critical in C17-boronation over a competing C7-boronation in related indole derived substrates. After oxidation of the C17–B bond to introduce the C17-ether, the C3–C21 bond of the targets is secured under the Mitsunobu reaction conditions with the vinylogous urethane as the nucleophilic component.
Construction of the Pentacyclic Core and Formal Total Synthesis of (rac
)-Renieramycin T