There is provided a novel pyrrole-imidazole polyamide compound for alkylating the specific base sequence of DNA, the polyamide compound being capable of being synthesized through fewer reaction steps than known hybrid molecules and having a combination of a high reactivity in DNA alkylation and the ability to recognize a sequence. Furthermore, there is provided an alkylating agent and a molecule serving as a drug, the alkylating agent and the molecule containing the polyamide compound. An indole derivative is represented by general formula (1): wherein R 1 represents a functional group for alkylating DNA; R 2 represents a hydrogen atom, an alkyl group, or an acyl group; and X represents a divalent group having one constitutional unit or having two or more constitutional units which may be the same or different, the constitutional unit being represented by the following formula: (wherein m is an integer of 0 to 10), wherein among the constitutional units, a terminal constitutional unit adjacent to R 2 may be a constitutional unit represented by the following formula: (wherein k is an integer of 0 to 10). |