Potassium carbonate (650 mg) was added to a solution of 2-butoxy-8-methoxy-9H-purin-6-amine trifluoroacetate salt (550 mg) in dry N,N-dimethylformamide (5.5 ml) and the reaction mixture heated at 60° C. for 1 hour. 1,1-Dimethylethyl 4-(bromomethyl)-1-piperidinecarboxylate (500 mg) was added using additional DMF (1.5 ml) to transfer the residual bromide and the reaction mixture stirred at 50° C. for 3 hours. After 16 hours at room temperature, heating at 50° C. was continued for another 5 hours to complete the reaction. Water was added and the reaction mixture extracted three times with ethyl acetate. The combined organic extracts were washed with water, dried over anhydrous sodium sulfate, filtered, concentrated and dried under high vacuum. Purification by chromatography on silica gel eluting with a gradient of 1-2.5% methanol in chloroform afforded the title compound as yellow solid (640 mg).
