The condensation of 5-methylindoline (I) with benzonitrile (II) by means of BCl3 and AlCl3 in dichloroethane gives the 7-benzoyl-5-methylindoline (III), which is cyclized with glycine methyl ester (IV) in pyridine yielding the tricyclic pyrrolobenzodiazepinone (V). The reaction of (V) with isoamyl nitrite and potassium tert-butoxide in THF affords the oxime (VI), which is reduced with H2 over Ru/C in methanol providing the racemic amine (VII). The optical resolution of (VII) with N-acetyl-L-phenylalanine gives the desired isomer (VIII), which is finally condensed with pyridine-4-carboxylic acid (IX) by means of O-[1-(ethoxycarbonyl)-1-cyanomethyleneamino]-N,N,N',N'-tetramethyluronium tetrafluoroborate (TOTU) and DIEA in dichloromethane.