L-Pyroglutamic Acid → Methyl 5-oxo-L-prolinate

Participants

Reaction Steps

To a solution of L-pyroglutamic acid (32.7 g, 0.253 mol) in methanol (600 mL) was added thionyl chloride (2.40 mL, 32.9 mmol), and the resulting solution was stirred at room temperature for 16 h. The reaction mixture was neutralized to pH=7 with saturated aqueous sodium bicarbonate and concentrated in vacuo. The residue was dissolved in methylene chloride, washed with brine, dried over magnesium sulfate, and concentrated. The residue was distilled under high vacuum to give the product as a colorless oil (28.9 g, 80%), b.p. 118-126° C./0.35 mm Hg. 1H NMR (300 MHz, CDCl3): δ 2.36 (m, 4 H), 3.77 (s, 3 H), 4.27 (dd, 1 H, J=5.0, 8.4), 6.78 (s, 1 H).

Provenance & Evidence