2,6-disubstituted and 2,6,8-trisubstituted purines as adenosine receptor antagonists

Purines have long been exploited as adenosine receptor antagonists. The substitution pattern about the purine ring has been well investigated, and certain criteria have become almost a prerequisite for good affinity at the adenosine A(1) receptor. The adaptation of the pharmacophore and the initial series of pyrimidines developed in an earlier publication resulted in a series of purines with an entirely new substitution pattern. One compound in particular, 8-cyclopentyl-2,6-diphenylpurine (31, LUF 5962) has been shown to be very promising with an affinity of 0.29 nM at the human adenosine A(1) receptor.