tert-butyl 5-oxo-L-prolinate

• As a starting material/synthon in the synthesis of angiotensin-converting enzyme inhibitors.
• In the synthesis of phenanthroindolizidine alkaloids named (+)-tylophorine and antofine.
• As a starting material in the synthesis of radioligands [¹⁸F]IUR-1602 and [¹⁸F]IUR-1601, applicable for imaging of P2X7R, a therapeutic target for neuroinflammation.

540-88-5

98-79-3

35418-16-7

[0492] L-Pyroglutamic acid (5.0 g, 38.73 mmol) was dissolved in tert-butyl acetate (65 mL, 0.48 mol) under nitrogen protection, followed by the slow addition of 70% aqueous perchloric acid (1.25 mL). The reaction mixture was placed in a 250 mL round bottom flask and stirred for 18 hours at room temperature. Upon completion of the reaction, the mixture was carefully poured into saturated aqueous sodium bicarbonate solution to neutralize the excess acid. The aqueous phase was extracted with ethyl acetate (200 mL × 2), and the organic phases were combined and dried over anhydrous sodium sulfate. The organic phase was concentrated under reduced pressure and the residue was recrystallized from a solvent mixture of hexane/ether (10:1). The resulting white solid was collected by filtration and dried to give the title compound (S)-tert-butyl 5-oxopyrrolidine-2-carboxylate S2 (5 g, 70% yield).