(−)-Exiguolide (1), isolatedfrom the marine sponge Geodia exigua, has been shown to inhibit the growth of the A549 human lung adenocarcinoma and NCI-H460 human lung large cell carcinoma cells in vitro. In this study, we synthesized structural analogues of 1 to explore its skeletal structure–activity relationships and found that the C18 methyl group and the configuration of the C16–C17 double bond