PROBLEM TO BE SOLVED: To provide a betulin derivative having water solubility and antitumor effect higher than those of betulin.SOLUTION: An antitumor agent contains as an active ingredient a betulin derivative represented by formula (1) and/or a pharmaceutically acceptable salt thereof [n1 and n2 are each independently 1 or 2].SELECTED DRAWING: NoneCOPYRIGHT: (C)2017,JPO&INPIT【課題】ベツリンよりも高い水溶性と抗腫瘍効果を有するベツリン誘導体。【解決手段】式(1)で示されるベツリン誘導体及び/又はその薬学的に許容される塩を有効成分として含有する抗腫瘍剤。[n1及びn2は各々独立に1又は2]【選択図】なし