Introduction of a nitroxide group on position 2 of 9-phenoxyacridine: Easy access to spin labelled DNA-binding conjugates

In the search for spin labelled intercalators of general use to construct DNA-binding conjugates, 6-chloro-2-[(1-oxyl-2,2,5,5-tetramethyl-pyrrolin-3-yl)methyloxy]-9-phenoxy-acridine 5, has been prepared. This key-intermediate reacts with amines to give the corresponding labelled 9-amino substituted acridines. Comparative EPR and fluorescence measurements show that the label causes only little modification of the binding properties of acridine.