A mixture of 0.106 g (0.28 mmol) of the product from Step 9 (25), 0.15 g (0.84 mmol) of tert-butyl 3-aminopropylcarbamate, and 0.005 g (0.03 mmol) of potassium iodide in 5 mL of DMF was stirred at 60° C. under nitrogen for 24 hours. The reaction was quenched with water, extracted with ethyl acetate (4×) and the combined organic layers were washed with saturated NaHCO3 and brine and dried over MgSO4. The solvent was removed in vacuo and the crude reaction mixture was subjected to flash chromatography on a 7 cm column. Elution with a gradient of 50% ethyl acetate in hexanes, 100% ethyl acetate, 3% methanol and 0.1% ammonia in DCM, and 10% methanol and 0.1% ammonia in DCM yielded 0.019 g (0.04 mmol, 15%) of tert-butyl 3-{[1-(3-benzyl-4-oxo-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidin-2-yl)propyl]amino}propylcarbamate (26) as a clear oil.
