| Abstract: | The synthesis of streptonigrin or its tricyclic (ABC) analogues by the Friedlander condensation requires a 2-nitrobenzaldehyde with all the necessary functionalities. A number of alternative syntheses are examined. It is shown that oxidation of 8-amino-5,6-dimethoxy-2,2-pyridylquinoline leads to 8-amino-2,2-pyridylqunoline-5,6-dione instead of 6-methoxy-2,2-pyridylquinoline-5,8-dione. The synthesis of two useful precursors: 4-bromo-3-hydroxy-5,6-dimethoxy-2-nitrobenzaldehyde and 4-bromo-3-hydroxy-5-methoxy-2-nitrobenzaldehyde is described. |
