[CH2:1]([O:3][C:4](=[O:9])[CH2:5][C:6](Cl)=[O:7])[CH3:2].C[O:11][C:12](=O)[CH2:13][C:14]1([NH2:17])[CH2:16][CH2:15]1.C(N(CC)CC)C.C([O-])(O)=O.[Na+]>C(Cl)Cl>[CH2:1]([O:3][C:4](=[O:9])[CH2:5][C:6]([NH:17][C:14]1([CH2:13][CH:12]=[O:11])[CH2:16][CH2:15]1)=[O:7])[CH3:2]
Chlorocarbonyl-acetic acid ethyl ester (2.75 ml; 22.1 mmol) is added dropwise under stirring and cooling to a solution of (1-amino-cyclopropyl)-acetic acid methyl ester (Chemstep Product List, 13926) (3.00 g; 23.2 mmol) in triethylamine (6.4 ml; 46.2 mmol) and CH2Cl2 (150 ml). After stirring at room temperature for 30 minutes, the reaction mixture is poured on a saturated solution of NaHCO3 and extracted with CH2Cl2 three times. The combined organic phases are dried over Na2SO4, filtered and evaporated to dryness. Purification via chromatography (SiO2; hexane/acetone 6:4) yield the title compound as crystalline light-yellow solid (1.9 g; 34%) 1H-NMR (400 MHz; DMSO-d6): 8.40 (s, 1H); 4.07 (q, 2H); 3.60 (s, 3H); 3.12 (s, 2H); 2.58 (s, 2H); 1.17 (t, 3H); 0.71 (m, 2H); 0.66 (m, 2H). MS (m/z) ES+: 244 (MH+)
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