The present invention relates to1299A - (chloromethyl) - 5-hydroxy-1 corresponding to the sixth position in the 9a tetrahydrocyclopropa [C] benz [e] indol - 4 - one skeleton2 - dihydro - possessed functional groups at the 7th position of the 3H benzo [e] indol skeletonThe aim of this study is to provide a novel dococarcin derivative which shows high cytotoxicity.The present invention provides a India phosphorus derivative or its pharmacally acceptable salt represented by the following formula.本発明は、1,2,9,9a-tetrahydrocyclopropa[c]benz[e]indol-4-one骨格での6位に相当する1-(chloromethyl)-5-hydroxy-1,2-dihydro-3H-benzo[e]indol骨格の7位に官能基を有し、高い細胞毒性を示す新規なDuocarmycin誘導体を提供することを目的としている。本発明は、下式に代表されるインドリン誘導体又はその薬理学的に許容される塩を提供する。