Synthesis
General procedure for the synthesis of (S)-1-N-benzyloxycarbonylproline from N-benzyloxycarbonyl-L-proline: 1-{[(phenylmethyl)oxy]carbonyl}-L-proline (8.0 g, 32.09 mmol) was solubilized in 1,4-dioxane (40 mL), and pyridine (1.5 mL) and di-tert-butyl dicarbonate ((Boc)2O, 9.1 g 41.72 mmol). Ammonium bicarbonate (3.2 g, 40.43 mmol) was then added. The reaction mixture was stirred at room temperature overnight and then diluted with ethyl acetate (100 mL) and washed sequentially with water (50 mL) and 5% sulfuric acid (H2SO4). The organic layer was separated, dried over anhydrous sodium sulfate (Na2SO4) and filtered. The solvent was removed by distillation under reduced pressure to give a clarified oil. The oily material was ground with ether, the precipitate was collected by filtration and dried under vacuum to afford (S)-1-N-Benzyloxycarbonylprolinamide as a white solid (3.9 g, 49% yield). The mass spectrum showed [M+H]+ of 249.
References
[1] Organic and Biomolecular Chemistry, 2005, vol. 3, # 1, p. 84 - 96
[2] Synlett, 2004, # 3, p. 558 - 560
[3] Patent: WO2005/121135, 2005, A1. Location in patent: Page/Page column 240-241
[4] Canadian Journal of Chemistry, 2007, vol. 85, # 2, p. 85 - 95
[5] Journal of the American Chemical Society, 2018, vol. 140, # 5, p. 1627 - 1631
