Synthesis of Novel Isoquinolino[5,4- ab ]phenanthridine Derivatives via Pictet-Spengler Reaction

The reaction of 5-amino-2-[2-(dimethylamino)ethyl]-6-phenyl-1 H -benzo[ de ]isoquinoline-1,3(2 H)-dione with a series of aldehydes in acidic media (phosphoric acid, trifluoromethanesulfonic acid, and trifluoroacetic acid) is described. This key step is based on the Pictet-Spengler reaction to synthesize ten novel isoquinolino[5,4- ab ]phenanthridine derivatives. The most effective acid is phosphoric acid and optimized yields were obtained. The frameworks of target compounds are unique and have never been reported.