The general procedure for the synthesis of (S)-2-amino-4-methylpentanamide from L-leucine methyl ester was as follows: to a 250 mL 24/40 interface single neck round bottom flask fitted with a stirrer was added a 10 mL methanol solution of 8.1 g (0.056 mol) of L-leucine methyl ester under nitrogen protection. Subsequently, 40 mL of a 28-30% solution of ammonia was added slowly and dropwise over about 20 minutes. The reaction was stirred continuously under nitrogen atmosphere for 72 hours. Upon completion of the reaction, the solution was concentrated under vacuum at a pressure of 5-10 mmHg using a rotary evaporator (Model: 13uchi Rotovapor R-124, Manufacturer: I3UCHI Seikagaku Corp., Switzerland). The concentrated residue was dissolved in 250 mL of water and extracted with dichloromethane (5 × 500 mL). The organic layers were combined into a 4 L conical flask and dried by adding anhydrous sodium sulfate. After filtration to remove the desiccant, the organic phase was again concentrated using a rotary evaporator at a pressure of 5-10 mmHg, resulting in 5 g of the white solid product (S)-2-amino-4-methylpentanamide.
