N-Boc-L-proline is used as an intermediate in organic synthesis. It is also used to prepare daclatasvir, which inhibits the hepatitis C virus (HCV) non-structural 5A (NS5A) protein. Further, it is used as a drug in the treatment of hepatitis C virus (HCV).
Triethylamine (16.5 mL, 0.12 mmol) was added dropwise over a period of 10 min to a stirred, ice-cold suspension of l-proline (10.0 g, 8.7 mmol) in dichloromethane (200 mL) in a 500-mL three-necked, round-bottomed flask. A solution of Boc2O (28.3 g, 0.13 mmol) in dichloromethane (100 mL) was then added over a period of 10 min and the mixture was stirred for 2.5 h. Thereafter, 10% aqueous citric acid (50 mL) was added, and the dichloromethane layer was washed with saturated brine (2×50 mL) and with water (50 mL). After drying the organic phase over magnesium sulfate, the solvent was evaporated and the residue was taken up in hot ethyl acetate. Dilution of this solution with hexane gave the product, N-tertbutoxycarbonyl- L-proline (17.8 g, 95%); mp 138–140℃; TLC (silica gel): Rf=0:36 (EtOAc/MeOH, 1:1).
