Synthesis and biological evaluation of 2-amino-3-(4-chlorobenzoyl)-4-[N-(substituted) piperazin-1-yl]thiophenes as potent allosteric enhancers of the A1 adenosine receptor

The synthesis and evaluation of a series of 2-amino-3-(4-chlorobenzoyl)-4-[4-(alkyl/aryl)piperazin-yl]thiophene derivatives as allosteric enhancers of the A 1-adenosine receptor are described. The nature of substituents on the phenyl ring tethered to the piperazine seem to exert a fundamental influence on the allosteric enhancer activity, with the 4-chlorophenyl 8f and 4-trifluoromethyl 8j derivatives being the most active compounds in binding (saturation and displacement experiments) and functional cAMP studies.