Pyrrolidone carboxylic acid → Methyl 5-oxo-DL-prolinate

Participants

Reaction Steps

To a solution of DL-pyroglutamic acid (50 g, 0.387 mol) in 157 mL CH3OH (3.87 mol) and 100 mL toluene was added concentrated H2SO4 (2.5 mL). This mixture was warmed to reflux and allowed to stir for 16 h. Since starting material remained, another 4 mL concentrated H2SO4 was added and the mixture stirred at reflux for an additional 24 h then was cooled to ambient temperature and 20% aqueous NaOH was added to bring the solution to pH ˜6. The mixture was concentrated under reduced pressure and the residue was dissolved in CH2Cl2, filtered through Celite® diatomaceous earth, concentrated and purified via Kugelrohr distillation. The resulting material was carried on directly to the next reaction.

Provenance & Evidence