Step 2: Diethyl 2-((1H-pyrrolo[2,3-b]pyridin-3-yl)methyl)-2-acetamidomalonate (3.5 g, 10.08 mmol) was mixed with 37% hydrochloric acid (30 mL) and the reaction was carried out at reflux for 15 hrs. Upon completion of the reaction, the mixture was concentrated to about 10 mL. acetonitrile (5 mL) was added to the concentrate and subsequently lyophilized to give an off-white solid product. The solid was redissolved in 15% aqueous ammonia solution, pH adjusted to 7, and then diluted with water (20 mL). The precipitated white solid was collected by filtration, washed sequentially with water and ethanol, and dried to give 2-amino-3-(1H-pyrrolo[2,3-b]pyridin-3-yl)propanoic acid (1.5 g, 72.5% yield) as a white solid. The product was analyzed by LCMS (condition A): retention time = 0.29 min; ESI-MS (+) m/z 206.0 ([M+H]+).
