Abstract:
Leonuketal (8) is a seco-labdane natural product isolated from Leonurus japonicus, or Chinese liverwort, a herb used in traditional Chinese medicine. Leonuketal (8) exhibits vasorelaxant properties against KCl-induced contraction of rat aorta with an EC₅₀ value of 2.32 μM, and bears a complex tetracyclic structure. The carbon skeleton of 8 is derived from scission of the labdane B-ring, thus designating 8 a member of an interesting sub-class of diterpenoid natural products termed seco-labdanes. The architectural complexity of leonuketal (8) makes it an attractive target for total synthesis; herein the evolution of a synthetic strategy towards that end is described...