8-Substituted 2-alkynyl-N9-propargyladenines as A2A adenosine receptor antagonists

Structure-activity relationships of 2-alkynyladenine derivatives were explored by varying substituents at the 9-, 8- and 2-positions of the purine moiety in order to optimize A(2A) adenosine receptor antagonist activity in vitro. A propargyl group at the 9-position was found to be important for A2A antagonist activity, and the introduction of a halogen, aryl, or heteroaryl at the 8-position further enhanced activity. A series of 8-substituted 2-alkynyl-N-9-propargyladenine derivatives exhibited potent antagonist activity, with IC50 values in the low nM range. Compound 4a from this series was found to be orally active at a dose of 3 mg/kg in a mouse catalepsy model and a 6-hydroxydopamine-lesioned rat model of Parkinson's disease. (C) 2014 Elsevier Ltd. All rights reserved.