The title compound, 2,10-dihydroxy-1,6,10-trimethyl-4,14-dioxatricyclo[9.2.
1.0(3.7)]tetradecan-5-one, C15H24O5, a novel sesquiterpene lactone synthesi
zed from dihydroparthenolide, has a 1,4-furano bridge in the 10-membered ri
ng and a transfused alpha -methyl-gamma -lactone.