Synthesis of N-acridinyl-N′-alkylguanidines: Dramatic influence of amine to guanidine replacement on the physicochemical properties

Transformation of aminoacridines into N-acridinyl-N′-alkylguanidines is described. The chosen procedure allows introduction of pendent substituents (exemplified by N,N-dimethylaminopropyl chain) into key acridinyl thioureas, thus opening the way to structural diversity. Spectroscopic study and pKa determination show that the presence of the strongly basic guanidine has a dramatic influence on the ionization of the acridine nucleus by lowering the pka value down to 4.49.