Progress toward an asymmetric total synthesis of the Stemona alkaloid tuberostemoninol

Presented herein is a twenty-five linear step synthetic progress toward an asymmetric total synthesis of the Stemona alkaloid tuberostemoninol. A diastereoselective intramolecular Pauson-Khand reaction of a glycinate derivative served to construct the BC ring system and set one of the two quaternary carbon centers present in the target molecule in high yield. The gamma-lactone E ring and azepine D ring were constructed subsequently. Several approaches were explored for the introduction of the gamma-lactone E ring carbon skeleton containing the alpha-methylene group. Further elaboration of the BCDE tetracycle toward tuberostemoninol was performed to afford the corresponding ketone compound, which makes completion of the total synthesis possible in ten steps.