(R)-(-)-1-(2-Pyrrolidinylmethyl)pyrrolidine

Synthesis

Using (+)-Cbz-D-proline (1.5 g, 6 mmol) as raw material, EDC (2.3 g, 12 mmol), HOBt (800 mg, 6 mmol), TEA (1.5 mL), and pyrrolidine (853 mg, 12 mmol) were sequentially added in DMF (20 mL) and the reaction was stirred at room temperature for 18 hours. After completion of the reaction, the reaction solution was diluted with water and sodium bicarbonate and extracted with dichloromethane (3 x 20 mL). The organic phases were combined, concentrated and purified by silica gel column chromatography to afford benzyl (R)-2-(pyrrolidine-1-carbonyl)-pyrrolidine-1-carboxylate. The resulting benzyl ester of (R)-2-(pyrrolidine-1-carbonyl)-pyrrolidine-1-carboxylate was dissolved in methanol, Pd/C catalyst was added and hydrogenated at room temperature for 20 h. After completion of the reaction, the catalyst was removed by filtration and the filtrate was concentrated to give pyrrolidin-1-yl-(R)-pyrrolidin-2-yl- methanone. Pyrrolidin-1-yl-(R)-pyrrolidin-2-yl-methanone (1.2 g, 7.1 mmol) was dissolved in THF (10 mL) at 0 °C and B2H6 (10 mL, 10 mmol) was added slowly. The reaction mixture was heated to reflux and reacted for 16 hours. Upon completion of the reaction, the reaction solution was acidified with HCl and concentrated to remove the solvent. The residue was adjusted to pH 10 with 2N NaOH and extracted with dichloromethane solution containing 5% methanol. The organic phases were combined, concentrated and purified by silica gel column chromatography to afford the target product (R)-1-(2-pyrrolidinylmethyl)pyrrolidine 800 mg in 73% yield.

References

[1] Journal of Medicinal Chemistry, 1992, vol. 35, # 23, p. 4334 - 4343
[2] Patent: WO2004/76412, 2004, A2. Location in patent: Page 98
[3] Patent: US2003/125370, 2003, A1
[4] Patent: WO2017/17630, 2017, A1. Location in patent: Page/Page column 50