1. 3-Methoxypropionic acid (1.81 mL, 19.2 mmol) was suspended in anhydrous acetonitrile (80 mL) and stirred. 2. Methyl 5-methoxy-3-oxopentanoate (3.24 g, 20.0 mmol) was added in one portion and the reaction mixture was stirred at room temperature for 1.5 h. 3. A powdered mixture of magnesium chloride (1.57 g, 16.5 mmol) and potassium methyl malonate (4.5 g, 28.8 mmol) was added in one portion (note that CO2 gas was produced during the reaction). 4. The reaction mixture continued to be stirred at room temperature. 5. MgCl2 (1.57 g, 16.5 mmol) and potassium malonate monohydrate (4.5 g, 28.8 mmol) in a powdered mixture (note that CO2 gas is produced during the reaction). 4. Continue to stir the reaction mixture at room temperature. 5. Vacuum remove the volatiles, then add 2M hydrochloric acid (105 mL). 6. Stir the solution for 1 hour at room temperature, and then extract it with dichloromethane (3 x 100 mL). 7. Combine the organic phases, dry them with MgSO4, filter, and remove the solvents in vacuum. 8. dried, filtered and the solvent was removed in vacuum to afford the target product methyl 5-methoxy-3-oxovalerate (2.69 g, 87% yield).
