NEW MATERIAL:An aphidicolane derivative expressed by formula I [NR1R2 is amino, mono- or di-lower alkylamino, formula II (X is CH2, NH or O; n is 0 or 1) or phthalimide] or its acid addition salt.

EXAMPLE: 3α,16β,18-Trihydroxy-17-phthalimidoaffidicolan.

USE: An antitumor agent.

PREPARATION: A compound expressed by formula III is reacted with a monoor a di-lower alkylamine, a compound expressed by formula IV or phthalimide to afford the compound expressed by formula I (NR1R2 is other than NH2) or a compound expressed by formula V is reacted with hydrazine to provide the compound expressed by formula I (NR1R2 is NH2). Furthermore, the aforementioned compound is stable as opposed to properties of conventionally well- known affidicolin-17-glycinate hydrochloride, etc., and basicity will not be readily lost in blood.