Such organic ligands were chosen in connection with the fact that 6-oxo-9-deazapurines themselves show various types of biological activities, e.g., they behave as potential purine nucleoside phosphorylase (PNP) inhibitors, possess immunosuppressive ability, which could be beneficial in the treatment of T-cell proliferative and autoimmune diseases [19]. Here, PNP is linked to autoimmune disease.