Reaction #1810811

Reaction equation

sodium carbonate

Perchloric acid

(S)-pyroglutamic acid

tert-butyl acetate

→

ester

Yield 56.4%

(S)-tert-Butyl pyroglutamate

Yield 56.4%

Solvents

ether

carbon tetrachloride

Conditions

Workup

1. 1
   Washthe organic phase washed with saturated sodium hydrogen carbonate solution and brine
2. 2
   ExtractionThe aqueous phase was extracted with ethyl acetate
3. 3
   Dryingdried (MgSO4)
4. 4
   Filtrationfiltered
5. 5
   Otherthe solvent removed
6. 6
   Otherto yield an oil to which
7. 7
   Otherthe solvent evaporated in vacuo
8. 8
   Otherto remove traces of acetic acid

Procedure

Perchloric acid (70% aqueous, 0.521 cm3, 6.05 mmol) was added dropwise to a stirred suspension of (S)-pyroglutamic acid 9 (1 g, 7.75 mmol) in tert-butyl acetate (12 cm3, 85.5 mmol). The mixture was stirred for 24 h then sodium carbonate (0.80 g, 7.60 mmol) was added cautiously, ether was added and the organic phase washed with saturated sodium hydrogen carbonate solution and brine. The aqueous phase was extracted with ethyl acetate, dried (MgSO4), filtered and the solvent removed to yield an oil to which was added carbon tetrachloride and the solvent evaporated in vacuo to remove traces of acetic acid to give ester 10 (0.81 g, 56%) as a white solid: δH (300 MHz; CDCl3; Me4Si) 1.48 [9H, s, C(CH3)], 2.33-2.45 (4H, m, 3-H2, 4-H2), 4.12-4.16 (1H, m, 5-H) and 6.16 (1H, br s, N—H); δC (75 MHz; CDCl3) 24.7 (CH2, 4-C), 27.8 [CH3, C(CH3)], 29.2 (CH2, 3-C), 55.9 (CH, 5-C), 82.3 [quat., C(CH3)], 170.9 (quat., 5-CO) and 177.7 (quat., 2-C).

Source