Step 2: Synthesis of methyl 3-(cyclopentylamino)propionate; Methyl 3-aminopropionate (9.37 g, 0.09 mol) was dissolved in dichloromethane (DCM, 200 mL), and cyclopentanone (6.43 mL, 0.07 mol), sodium acetate (5.96 g, 0.07 mol), and sodium triacetoxyborohydride (22 g, 0.10 mol) were added in turn . The reaction mixture was stirred at room temperature for 16 hours. After completion of the reaction, 20% sodium bicarbonate solution (100 mL) and 2M sodium hydroxide solution (50 mL) were added and separated by extraction with dichloromethane/water (DCM/H?O). The organic phases were combined, washed with saturated sodium chloride (NaCl) solution, dried with anhydrous magnesium sulfate (MgSO?), filtered, and the filtrate was concentrated under reduced pressure and then dried under vacuum to obtain the light yellow oily target product methyl 3-(cyclopentylamino)propionate (8.90 g, 55% yield); the molecular ion peak was detected in the positive mode of mass spectrometry (MS) m/z: 172.4.
