To a suspension of NaH (0.49 g, 16.3 mmol, 80%) in THF (15 mL) at 0° C. was added diethyl malonate (2.61 g, 16.3 mmol). The mixture was stirred for 15 min and was then added dropwise to a refluxed mixture of (5-bromomethyl-pyridin-2-yl)-carbamic acid tert-butyl ester (3.90 g, 13.6 mmol) in THF (25 mL), and the resulting solution was refluxed for 15 min. After evaporation of the solvent, the crude product was purified by flash chromatography (methanol/CH2Cl2, 1:100→2.5:100) to give 2-(6-tert-butoxycarbonylamino-pyridin-3-ylmethyl)-malonic acid diethyl ester (2.18 g, 44%).
