This compound can be obtained in two different ways: 1) By direct nitration of camptothecin (I) with nitric acid in sulfuric acid. 2) By direct nitration of camptothecin (I) with different inorganic nitrates (or mixtures of inorganic nitrates) in sulfuric acid. 3) The reaction of 2,6-dinitrobenzaldehyde (II) with ethylene glycol (III) and p-toluenesulfonic acid in refluxing toluene gives the corresponding ethylene ketal (IV), which is reduced with sodium sulfide in refluxing ehanol/water yielding 2-amino-6-nitrobenzaldehyde ethylene ketal (V). The hydrolysis of (V) with aqueous sulfuric acid affords 2-amino-6-nitrobenzaldehyde (VI), which is finally cyclized with the tricyclic ketone (VII) in refluxing acetic acid (the same cyclization can be performed with the ketal (V) and the ketone (VII).
9-Amino-20(S)-camptothecin is obtained by nitration of camptothecin (I) with fuming nitric acid in concentrated sulfuric acid yielding the intermediate 9-nitrocamptothecin (II), which is then reduced with H2 over PtO2 in absolute ethanol.