C([O:3][C:4]([C:6]1[N:7]=[C:8]([C:11]2([NH:14][C:15]([O:17][CH2:18][C:19]3[CH:24]=[CH:23][CH:22]=[CH:21][CH:20]=3)=[O:16])[CH2:13][CH2:12]2)[O:9][CH:10]=1)=[O:5])C.[OH-].[Na+].Cl>C1COCC1>[CH2:18]([O:17][C:15]([NH:14][C:11]1([C:8]2[O:9][CH:10]=[C:6]([C:4]([OH:5])=[O:3])[N:7]=2)[CH2:13][CH2:12]1)=[O:16])[C:19]1[CH:20]=[CH:21][CH:22]=[CH:23][CH:24]=12-(1-Benzyloxycarbonylamino-cyclopropyl)-oxazole-4-carboxylic acid ethyl ester (0.44 g, 1.3 mmol) was dissolved in THF (10 mL) and to this solution was added 2N NaOH (2.0 mL, 4.0 mmol). The mixture was heated at 70° C. for 17 h. The mixture was neutralized with 2N HCl and extracted with EtOAc (3×100 mL). The combined extracts were washed with water, brine and dried with MgSO4. The mixture was filtered and concentrated to give 2-(1-benzyloxycarbonylamino-cyclopropyl)-oxazole-4-carboxylic acid (0.22 g, 0.73 mmol) as a brown solid.
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