Dehydro-leucodin: A guaiane-type sesquiterpene lactone

Abstract

Dehydro-leucodin [systematic name: (1S,6S,2R)-9,13-dimethyl-5-methylene-3- oxatricyclo-[8.3.0.02,6]trideca-9,12-diene-4,11-dione], C 15H16O3, is a guanolide isolated from Artemisia douglasiana. The fused-ring system contains a seven-membered ring that adopts a chair conformation, a fused planar cyclopentenone ring and a five-membered lactone ring fused in envelope conformation. The absolute structure determined by X-ray analysis agrees with that previously assigned to this compound by NMR studies [Bohlmann & Zdero (1972). Tetrahedron Lett. 13, 621-624] and also with that of leucodine, a closely related guaianolide [Martinez et al. (1988). J. Nat. Prod. 51, 221-228].