15761-39-4

54503-10-5

GENERAL METHOD: 20 g (93 mmol) of Boc-L-proline was dissolved in 150 mL of anhydrous acetonitrile, and 19.5 g (120 mmol) of 1,1'-carbonyldiimidazole, 21.0 mL (150 mmol) of trimethylamine, and 19.2 g (200 mmol) of ammonium carbonate were added sequentially. The reaction mixture was stirred at room temperature for 24 hours. Upon completion of the reaction, the mixture was poured into 250 mL of saturated potassium carbonate solution and extracted with dichloromethane (3 x 250 mL). The organic phases were combined, washed twice with 150 mL of water and dried over sodium sulfate. After removing the solvent under reduced pressure, the crude product was purified by rapid chromatography on silica gel with the eluent being ethylhexane-ethyl acetate (100:0→1:1). The product was obtained as 12.3 g in 62% yield. MS data: m/z (Irel, %) 215.1 (100) [M + H]+.