L-Pyroglutamic Acid → (S)-4-((5-Oxo-2-pyrrolidinyl)carbonyl)morpholine

Participants

Reaction Conditions

Reaction Steps

The reaction vessel is charged with 30 g L-pyroglutamic acid and 4.71 g 1-hydroxybenzotriazole hydrate. The solids are then suspended in 190 ml anhydrous acetonitrile and the mixture is then heated to 45° C. Subsequently, 20.24 ml morpholine is added via a dropping funnel within 20 min, and the dropping funnel is then washed with 5 ml anhydrous acetonitrile. The resulting mixture is then heated to 65° C. and 29.32 g N—N′-diisopropylcarbodiimide added within 1 h via a dropping funnel. After complete addition, the dropping funnel is washed with 5 ml anhydrous acetonitrile and the reaction mixture is stirred at 65° C. for an additional 30 min. The resulting suspension is then cooled to ambient temperature, filtered and the filter cake washed with 3×30 ml acetonitrile. The filtrate is concentrated under heating and reduced pressure to approx. ½ of its original volume and the residue is then seeded with 16 mg (S)-5-(morpholine-4-carbonyl)pyrrolidine-2-one. Concentration under reduced pressure is continued until approx ⅓ of the original volume of the filtrate is reached. While further concentrating the filtrate under reduced pressure and removing approx. 95 ml of distillate, simultaneously 210 ml 2-methyltetrahydrofuran is added. The suspension is then cooled to 0° C. and the solids are isolated by filtration. The filter cake is washed with 3×20 ml icooled 2-methyltetrahydrofuran and dried at 55° C. under vacuum to give 42.54 g of (S)-5-(morpholine-4-carbonyl)pyrrolidine-2-one as fine white crystals (98.0% purity by HPLC, ee (HPLC)>99.6% [4-a, R1=H; R4=morpholine]).

Provenance & Evidence