The design and synthesis of the two cytotoxic derivatives 15 and 16 of the novel pyrrolo[1',2':1,2][1,4]diazepin[7,6-b]in-dol-5(6H)-one nucleus is described. Readily available methyl 2-indolecarboxylates 5 and 6 are nitrosated with NaNO2 in AcOH to give the analogs 7 and 8, which are then oxidized with KMnO4 in aq. NaOH to provide the 3-NO2 acids 9 and 10. These, in turn, are subjected to amidation with (2S)-pyrrolidine-2-carboxaldehyde diethyl thioacetal in the presence of EDCI and HOBt and then to a 7-exo-trig cyclization reaction to give the target molecules 15 and 16. The new analogs were evaluated in the human leukemic K-562 cell line and were shown to have micromolar potency.