Synthesis
The general procedure for the synthesis of L-proline methyl ester hydrochloride from methanol and L-proline was as follows: first, methyl (S)-pyrrolidine-2-carboxylate was prepared by reacting (S)-proline (10.2 g, 88.6 mmol) with SOCl? (11.6 g, 7.10 mL, 97.5 mmol) in refluxed methanol (60 mL) for 29 hours. Upon completion of the reaction, excess solvent and SOCl? were removed by distillation under reduced pressure to afford the proline ester as a gray oil (15.9 g, quantitative yield). Subsequently, 2-fluoro-1-nitrobenzene (6.92 g, 5.18 mL, 49.0 mmol) was reacted with methyl (S)-pyrrolidine-2-carboxylate (7.55 g, 45.6 mmol) prepared as described above according to the literature method to afford bright yellow crystals of L-prolinylmethyl ester hydrochloride (12.0 g, quantitative yield), which was used without further purification for subsequent The product can be used for subsequent experiments without further purification.
References
[1] Heterocycles, 1986, vol. 24, # 4, p. 1045 - 1060
[2] Bulletin des Societes Chimiques Belges, 1994, vol. 103, # 5-6, p. 201 - 206
[3] Journal of the Chemical Society - Perkin Transactions 1, 1998, # 22, p. 3767 - 3775
[4] European Journal of Organic Chemistry, 2002, # 19, p. 3304 - 3314
[5] Tetrahedron, 2008, vol. 64, # 42, p. 9992 - 9998
