NCU-190Na is synthesized by condensation of naphthoquinone (I) and phenylenediamine (II), but several isomers (IV) of benzo[a]phenazine are produced at the same time. Using ethyl chlorocarbonate, (III) is selectively produced and aminolysis of esters is also selective to the 6-position; thus, (V) is produced and can be converted to (VI) (NCU190Na). Various derivatives of (VI) can be synthesized in a similar manner. Compound (III) can also be prepared from naphthoquinone (I) and ethyl chloroformate (VII) to give ethyl 3-(ethoxycarbonyloxy)-1,4-dioxo-1,4-dihydro-2-naphthoate (VIII), which is condensed with phenylenediamine (II).