7 H, 10-methoxy pyrido [3,2-c], [4,3-c] and [3,4-c] carbazoles, and 7 H-pyrido [2,3-c] carbazole were synthesized by oxidative photocyclisation, to achieve a topological analysis of intercalation in DNA. From these parent compounds we have prepared the corresponding iodomethylates, 7-methyl and 10-hydroxy derivatives.