An efficient synthesis of a new class of DNA intercalating antitumor 7,10-dihydroxy-6H-pyrazolo[4,5,1-de]acridin-6-ones

An efficient synthesis of KW-2170 (1), which is a 7,10-dihydroxy-6H-pyrazol o[4,5,1-de]acridin-6-one derivative and a new class of DNA intercalating an titumor agents, is described. The selective monobromination of the methyl g roup before the cyclization to the pyrazoloacridone is easily carried out. In the improved process, the bromination of the corresponding methyl group is achieved prior to the hydroquinone formation, so the protection of the h ydroxy groups is not necessary unlike the original method. In comparison wi th the original synthetic route of KW-2170 (1), the new route decreases the synthetic steps from 2-bromo-6-methoxybenzoic acid (2) from 15 to 13 and i ncreases the overall yield from 2 to 12%.