Two Total Syntheses of Trigoxyphins K and L.

Two total syntheses are presented for trigoxyphins K and L, tricyclic terpenoids from Trigonostemon xyphophylloides . The first proceeds via electrophlic cyclization in A/C-ring substrates to close the B ring at C4-C5 and then 1 O 2 -mediated hydroxybutenolide formation to trigoxyphin L, with Luche reduction leading to trigoxyphin K. The second route develops from tetralone ring expansion to a B/C-ring intermediate that, by one-step O-demethylation-lactonization-isomerization, affords trigoxyphin K and then trigoxyphin L following enolate oxygenation.