Cl.[NH2:2][C:3]1([C:6]([O:8][CH2:9][CH3:10])=[O:7])[CH2:5][CH2:4]1.C([O-])(O)=O.[Na+].Cl[C:17]([O:19][CH2:20][C:21]1[CH:26]=[CH:25][CH:24]=[CH:23][CH:22]=1)=[O:18]>C(OCC)(=O)C.O>[CH2:20]([O:19][C:17]([NH:2][C:3]1([C:6]([O:8][CH2:9][CH3:10])=[O:7])[CH2:5][CH2:4]1)=[O:18])[C:21]1[CH:26]=[CH:25][CH:24]=[CH:23][CH:22]=1A suspension of ethyl 1-aminocyclopropanecarboxylate hydrochloride (9.5 g, 57.3 mmol) in 450 mL of ethyl acetate was cooled to 0° C., a solution of NaHCO3 (39.5 g, 470.3 mmol) in 325 mL of water was added slowly. Then benzyl chloroformate (13.3 g, 78.2 mmol) was added drop-wise. The cold bath was removed and the mixture was stirred at room temperature for 16 hours. The organic phase was washed with 1N HCl (100 mL), saturated NaHCO3 solution (100 mL), brine (100 mL), and dried over anhydrous sodium sulfate. The drying agent was removed by filtration and the filtrate was concentrated to give a white solid. The solid was purified by column chromatography (silica gel, 200-300 mesh, eluting with a mixture of ethyl acetate and petroleum ether (1:3, v/v) to give ethyl 1-(benzyloxycarbonylamino)cyclopropanecarboxylate (13.7 g, 91%) as a white solid. MS: (M+H)+=286.1; 1H NMR (300 MHz, CDCl3): δ 7.37-7.32 (m, 5H), 5.13 (s, 2H), 4.70 (s, 1H), 4.13 (brs, 2H), 1.59-1.53 (m, 2H), 1.23-1.19 (m, 5H).
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