| abstract |
Following formula (1): (In the formula, each R is independently a hydrogen atom, a lower alkyl group, an aryl group, an allyl group, an aralkyl group, a halogen atom, a hydroxyl group, an amino group, R′O—, R ′ (C═O) —, R ′ (C═O) O— or R′O (C═O) —, wherein R ′ is an alkyl group having 1 to 5 carbon atoms) or a pharmaceutically acceptable salt thereof. An antitumor effect potentiator of an antitumor substance, comprising |