(-)-D-Pyroglutamic acid methyl ester

67-56-1

149-87-1

4931-66-2

The general procedure for the synthesis of methyl (S)-(+)-2-pyrrolidone-5-carboxylate from methanol and DL-pyroglutamic acid was as follows: DL-pyroglutamic acid (2150 g, 16.65 mol) was dissolved in a solvent mixture of methanol (2.0 L) and chloroform (2.0 L), and methanesulfonic acid (80 g, 0.83 mol) was added. This mixture was transferred to a Soxhlet extraction apparatus fitted with 3 molecular sieves and the reaction was refluxed under mechanical stirring for 5 days. Upon completion of the reaction, the solvent was removed by distillation under reduced pressure to afford methyl (S)-(+)-2-pyrrolidone-5-carboxylate as a yellow oil in 98% yield (16.3 mmol). The product could be used in the next reaction without further purification and its physicochemical properties were consistent with those reported in the literature.1H NMR (CDCl3, 400 MHz) δ ppm: 2.08-2.50 (m, 4H, CHCH2CH2), 3.77 (s, 3H, CH3), 4.29 (m, 1H, CH2CH2CH), 7.62 (br s, 1H, NH). NH).