N-Protection of indole derivative (I) with methoxymethyl chloride (MOM-Cl) by means of NaH in THF provides aldehyde (II), which is converted into protected indolo-phenanthridine dione derivative (V) by coupling with quinoline (IV) by means of lithium tetramethylpiperidide (LiTMP) in THF (in turn, (IV) can be prepared from carboxylic acid (III) by treatment with thionyl chloride (SOCl2) and diethylamine (Et2NH)). Finally, the target compound is obtained by removal of the MOM group of (V) by treatment with aqueous HCl.
N-Protection of indole derivative (I) with methoxymethyl chloride (MOM-Cl) by means of NaH in THF provides aldehyde (II), which is converted into protected indolo-phenanthridine dione derivative (V) by coupling with quinoline (IV) by means of lithium tetramethylpiperidide (LiTMP) in THF (in turn, (IV) can be prepared from carboxylic acid (III) by treatment with thionyl chloride (SOCl2) and diethylamine (Et2NH)). Finally, the target compound is obtained by removal of the MOM group of (V) by treatment with aqueous HCl, followed by selective oxidation of the pyridine nitrogen by means of m-CPBA.