Potent, Metabolically Stable 2-Alkyl-8-(2h-1,2,3-Triazol-2-Yl)-9h-Adenines As Adenosine A(2a) Receptor Ligands

Inhibition of adenosine A(2A) receptors has been shown to elicit a therapeutic response in preclinical animal models of Parkinson's disease (PD). We previously identified the triazolo-9H-purine, ST1535, as a potent A(2A)R antagonist. Studies revealed that ST1535 is extensively hydroxylated at the -1 position of the butyl side chain. Here, we describe the synthesis and evaluation of derivatives in which the -1 position has been substituted (F, Me, OH) in order to block metabolism. The stability of the compounds was evaluated in human liver microsomes (HLM), and the affinity for A(2A)R was determined. Two compounds, (2-(3,3-dimethylbutyl)-9-methyl-8-(2H-1,2,3-triazol-2-yl)-9H-purin-6-amine (3b) and 4-(6-amino-9-methyl-8-(2H-1,2,3-triazol-2-yl)-9H-purin-2-yl)-2-methylbutan-2-ol (3c), exhibited good affinity against A(2A)R (K-i=0.4nM and 2nM, respectively) and high invitro metabolic stability (89.5% and 95.3% recovery, respectively, after incubation with HLM for two hours).