Ether analogues of galiellalactone, methods of preparing the analogues, and use of the analogues in the treatment of cancer are disclosed. The analogues are of formula (I) or (II): ##STR00001##

A derivative of inula lineariifolia lactone A, and in particular, a dimethylamine 4-O-acetyl inula lineariifolia lactone A or a salt thereof, preparation of same, and an application of same in preparation of medicine for treating multiple sclerosis. The dimethylamine 4-O-acetyl inula lineariifolia lactone A compound is represented by formula I: ##STR00001##

Ether analogues of galiellalactone, methods of preparing the analogues, and use of the analogues in the treatment of cancer are disclosed. The analogues are of formula (I) or (II):

##STR00001##