1-phenylpyrazolo[3,4-d]pyrimidines;: Structure-activity relationships for C6 substituents at A1 and A2A adenosine receptors

Substitution of 1-phenylpyrazolo[3,4-d]pyrimidines at C6 with N-alkyl-2-thiopropionamide groups has resulted in a series of 18 compounds which have been evaluated for binding at A(1) and A(2A) adenosine receptors. introduction of an N-ethyl group gave increased affinity at both A(1) and A(2A) receptors for the amino compound 7b compared to the primary amide 7a. An additional hydrophobic pocket exists for substituents on the amide. This pocket allows an N-ethyl group for increased affinity at both A(1) and A(2A) receptors, allows larger alkyl groups at A(2A) receptors but not at A(1) receptors and there is an H-bond interaction requiring one H-bond donor. Molecular modeling studies have also enabled a proposal of the amino acid residues involved in ligand binding at both the A(1) and A(2A) receptors. (C) 2000 Elsevier Science Ltd. All rights reserved.