Synthesis and biological characterization of [ super(3)H] (2-amino-4,5,6,7- tetrahydrobenzo[b]thiophen-3-yl)-(4-chlorophenyl)-methanone, the first radiolabelled adenosine A sub(1) allosteric enhancer

Among the adenosine A sub(1) allosteric enhancers reported so far, compound (2-amino-4,5,6,7-tetrahydrobenzo[b]thiophen-3-yl)-(4-chlorophenyl) -meth anone 1 (named T-62) has shown biological properties similar to those of PD 81,723, the reference A sub(1) allosteric enhancer and it has been more fully pharmacologically investigated. The preparation of the radiolabelled form of compound 1 and its characterization by saturation binding experiments are reported. These studies allowed us to demonstrate for the first time the existence of a specific, allosteric site on the A sub(1) receptor.