1,2,3-triazole[4,5-d]pyridazines--IV. Preparation and adenosine receptor binding of new 4 and/or 7 aminoderivatives

This paper reports the continuation of the studies on the 4-aminosubstituted 1,2,3-triazole[4,5-d]pyridazine derivatives which had shown binding affinity towards adenosine receptors. Biological results confirmed the greater activity of a benzyl substituent in the 1 position and the receptorial stereoselectivity related to the higher and more selective A1 affinity of the 4-D(+)-alpha-methylbenzylamino enantiomer 1b. The 4-phenylhydrazino substituent has shown an interesting binding activity about equipotent towards A1 and A2 receptorial sites. A surprisingly elevated A1 affinity (Ki = 7 nM), 440 fold higher than A2 affinity, is presented by compound 1d, bearing a m-toluidino substituent.