The title compound was prepared by dissolving the 3-[2-[4-(4-fluorobenzoyl)piperidin-1-yl]ethyl]thieno[3,4-d]pyrimidine-2,4-dione from Example 10 (1.8 g, 4.6 mmol) in 10 ml of dimethylformamide at 0° C. After treating this solution with NaH (203 mg, 5 mmol) followed by 720 mg (5 mmol) of methyl iodide, the mixture was stirred at room temperature for 24 hours. The reaction was poured into water and extracted with CH2Cl2. The combined extracts were washed with water and brine and dried over MgSO4. Solvent removal produced a crude product which was purified by flash silica gel chromatography using 2% MeOH/CH2Cl2. The title compound was crystallized from CH2Cl2 /hexane to give a white solid (1.04 g, 54% yield), mp 176°-178° C.
