Synthesis of 3,6-disulfonated 4-aminonaphthalimides

Article abstract of DOI:10.1021/ja00415a033

3,6-Disulfonated 4-aminonaphthalimides are stable, highly fluorescent, water-soluble compounds. A general synthesis of these compounds is presented: a primary amine is condensed in aqueous acid with 4-amino-3,6-disulfonaphthalic anhydride, and the product is isolated as its crystalline potassium, sodium, or lithium salt. The anhydride, whose preparation is described in detail, is interesting because it is stable indefinitely in boiling water and crystallizes readily when the solution is cooled. Because of their intense yellow-green fluorescence, solubility in water, and ability to be bound to cells and tissues, two of these 4-aminonaphthalimides have proved useful as biological tracers, and their synthesis is described in detail.