with amide sidechains had the most potent anticanceractivity among all other known glycolipids, with an effective concentration of 20 nM, which is comparable to that of doxorubicin. Conversely, acyclic and macrocyclic daumone derivatives had drastically decreased anticanceractivity. Due to the high lipophilic nature of the novel glycolipid derivatives, we propose that the observed anticancer activity