Synthesis
General procedure for the synthesis of tert-butyl (S)-2-(1H-imidazol-2-yl)pyrrolidine-1-carboxylate from BOC-L-proline:
1. N-Boc-L-proline (10 g, 50.2 mmol) was dissolved in methanol (100 ml).
2. To the above solution, glyoxal (40% w/w aqueous solution, 25 g, 170.6 mmol) and ammonia (5N aqueous solution, 191 ml, 954 mmol) were added sequentially.
3. The reaction mixture was stirred at room temperature overnight.
4. After completion of the reaction, the reaction mixture was partitioned with dichloromethane and water.
5. The aqueous phase was extracted twice with dichloromethane.
6. The organic phases were combined and concentrated by evaporation under vacuum.
7. The residue was purified by rapid column chromatography on silica gel (methanol/dichloromethane, 0 to 3% gradient, then held at 3%) to afford tert-butyl (S)-2-(1H-imidazol-2-yl)pyrrolidine-1-carboxylate (9.87 g, 82% yield) as an off-white solid.
ESI-LCMS m/e Calculated value: C12H19N3O2 [M+] 237.1, measured value: 237.9 [M+H+].
References
[1] Patent: US2012/230951, 2012, A1. Location in patent: Page/Page column 101
[2] Patent: WO2011/15657, 2011, A1
[3] Patent: WO2011/54834, 2011, A1
[4] Patent: US2012/136027, 2012, A1
[5] Patent: WO2014/19344, 2014, A1
