NC1OC=C(C(OCC)=O)N=1.CC(OC(C)=O)=O.[C:19]([NH:22][C:23]1[O:24][CH:25]=[C:26]([C:28]([O:30]CC)=[O:29])[N:27]=1)(=[O:21])[CH3:20].[Li+].[OH-]>CCO>[C:19]([NH:22][C:23]1[O:24][CH:25]=[C:26]([C:28]([OH:30])=[O:29])[N:27]=1)(=[O:21])[CH3:20]1.0 g (6.41 mmol) ethyl 2-aminooxazole-4-carboxylate and 9.10 mL (96.3 mmol) Ac2O are stirred at r.t. over the weekend. Then the solvent is removed in vacuo. Some toluene is added and all volatile components are removed in vacuo again. This procedure is repeated three times. The crude product is used without further purification. b) 1.31 g (6.60 mmol) of ethyl 2-acetamidooxazole-4-carboxylate are added to 33 mL EtOH. 0.55 g (13.2 mmol) LiOH are added and the resulting mixture is stirred at r.t. over night. Then the EtOH is removed in vacuo and diluted aq. HCl is added and the resulting precipitate is collected, washed with cold water and dried. The resulting product is used without further purification.
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