Concise and Stereocontrolled Synthesis of the Tetracyclic Core of Daphniglaucin C

The tetracyclic core of daphniglaucin C was prepared from the known 4-keto-<i>N</i>-Boc methyl-l-prolinate in 15 steps with a cumulative yield of 14.7%. The key steps toward this core motif feature a reductive double bond transposition from an unactivated tertiary allylic alcohol, a Pd-catalyzed Stille coupling, and Dieckmann cyclizations