Dehydro-leucodin [systematic name: (1S,6S,2R)-9,13-dimeth-yl-5-methyl-ene-3-oxatricyclo-[8.3.0.0(2,6)]trideca-9,12-diene-4,11-dione], C(15)H(16)O(3), is a guanolide isolated from Artemisia douglasiana. The fused-ring system contains a seven-membered ring that adopts a chair conformation, a fused