Cl[C:2]([O:4][C:5]1[CH:10]=[CH:9][C:8]([N+:11]([O-:13])=[O:12])=[CH:7][CH:6]=1)=[O:3].[C:14]([C:17]1[CH:21]=[C:20]([CH2:22][OH:23])[O:19][N:18]=1)(=[O:16])[NH2:15].N1C=CC=CC=1>ClCCl>[C:2](=[O:3])([O:4][C:5]1[CH:6]=[CH:7][C:8]([N+:11]([O-:13])=[O:12])=[CH:9][CH:10]=1)[O:23][CH2:22][C:20]1[O:19][N:18]=[C:17]([C:14](=[O:16])[NH2:15])[CH:21]=12.84 g (14.07 mmol) of 4-nitrophenyl chloroformate are added portionwise to a solution of 2.00 g (14.07 mmol) of 3-carbamoylisoxazol-5-ylmethanol, 1.71 mL (21.11 mmol) of pyridine and 0.17 g (1.41 mmol) of N,N-dimethylaminopyridine in 15 mL of dichloromethane, cooled to about 0° C. The medium is stirred at 0° C. for 1 hour and then at room temperature for 1 hour. The precipitate formed is filtered off and then rinsed thoroughly with diisopropyl ether. After drying under vacuum at about 60° C., 3.12 g of expected product are obtained in the form of a white solid, which is used without further purification in the following step.
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