US8058259B2 - Substituted 4-{3-[6-Amino-9-(3,4-Dihydroxy-Tetrahydro-Furan-2-Yl)-9h-Purin-2-Yl]-Prop-2-Ynyl}-Piperidine-1-Carboxylic Acid Esters as A2AR Agonists