Stereoselective Total Synthesis of (±)-Alstoscholarisine E.

The shortest synthesis to date of (±)-alstoscholarisine E was accomplished in seven linear steps from commercially available reagents and 15.2% overall yield. The approach features a tandem vinylogous Mannich reaction and hetero-Diels-Alder reaction to access the core. A novel tactic to induce diastereoselective reduction of the cyclic vinyl ether was discovered, and a mild procedure to form the bridged aminal ring by partial reduction of the lactam ring via iridium-catalyzed hydrosilylation was developed.