N-Carbobenzyloxy or N-Cbz

Protection

Benzyl chloroformate (1.76 mL, 12.3 mmol) was added dropwise to a stirred and cooled (0°C) mixture of tert-butyl 4-aminohexahydrocyclopenta[b]pyrrole-l(2H)-carboxylate ( 1.4 g, 6.2 mmol) and triethylamine (3.5 mL, 24.7 mmol) in dichloromethane, and the resulting mixture was stirred at room temperature overnight. The reaction mixture was diluted with dichloromethane and washed with saturated aqueous NaHCO3 water and brine. The mixture was dried (MgSO4) filtered and the solvent was evaporated under reduced pressure. The residue was purified by column chromatography on silica gel, eluting with EtOAc/isohexane to give Compounds as colorless oil (78%). 

 

Patent reference: WO2010056717 (Merck)

Deprotection

A racemic mixture of trans-benzyl 3-(tert-butoxycarbonylamino)-4-hydroxypyrrolidine-1-carboxylate (3.36 g, 9.99 mmol) in MeOH (40 mL) was degassed, then 10 wt % Pd/C (3.19 g, 3.00 mmol) was added. The mixture was degassed, charged with H2, and stirred overnight. The mixture was filtered through a bed of Celite, washed with methanol, the filtrate was dried over anhydrous Na2SO4, filtered and conc., in vacuo to yield a white solid as racemic tert-butyl-4-hydroxypyrrolidin-3-ylcarbamate (2.020 g, 100 %).

 

Patent reference: WO2010001169 (Astrazeneca)

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