A solution of KOH (0.067 g, 1.03 mmol) in ethanol (3 mL) was added to a solution of 2-[1-(6-tert-butoxycarbonylamino-pyridin-3-yl)-2-phenyl-ethyl]-malonic acid diethyl ester (0.44g, 0.96 mmol) in ethanol (3 mL) and methylene chloride (2 mL) at 0° C. The mixture was stirred for 48 h at room temperature. The mixture was concentrated under reduced pressure and ethyl acetate and 0.5 M HCl were added to the residue. The organic layer was washed with brine and dried. Filtration and evaporation in vacuo gave 2-[1-(6-tert-butoxycarbonylamino-pyridin-3-yl)-2-phenyl-ethyl]-malonic acid monoethyl ester (0.37, 90%).
