L-Pyroglutamic Acid → tert-Butyl 5-oxo-L-prolinate

Reaction equation

[NH:1]1[C:5](=[O:6])[CH2:4][CH2:3][C@H:2]1[C:7]([OH:9])=[O:8].Cl(O)(=O)(=O)=O.C([O-])(O)=O.[Na+].C(O[C:24]([CH3:27])([CH3:26])[CH3:25])(=O)C>>[O:6]=[C:5]1[NH:1][C@H:2]([C:7]([O:9][C:24]([CH3:27])([CH3:26])[CH3:25])=[O:8])[CH2:3][CH2:4]1

Participants

Reactant 4

HCID 7405L-Pyroglutamic Acid

HCID 10908tert-Butyl acetate

HCID 24247Perchloric Acid

HCID 516892Sodium Bicarbonate2×

Product 1

HCID 10888648tert-Butyl 5-oxo-L-prolinateYield 72%

Procedure

To a suspension of L-pyroglutamic acid (13.2 g, 102 mmol) in t-butyl acetate (200 mL), was added perchloric acid (70%, 9.7 mL, 113 mmol). The mixture was stirred at rt for 20 h, then poured into sat. NaHCO3. NaHCO3 (s) was added until neutral. The aqueous phase was extracted with EtOAc (6×). The combined organic extract was dried (Na2SO4) and concentrated to afford 13.68 g (72%) of the title compound, 1a. 1H NMR (300 MHz, CDCl3) δ 6.17 (br s, 1H), 4.13 (dd, J=7.4, 5.2, 1H), 2.44–2.31 (m, 3H), 2.22–2.15 (m, 1H), 1.47 (s, 9H).