[NH2:1][C@H:2]1[CH2:8][CH2:7][C:6]2[CH:9]=[CH:10][CH:11]=[CH:12][C:5]=2[N:4]([CH2:13][C:14]([O:16][C:17](C)(C)[CH3:18])=[O:15])[C:3]1=[O:21].C1(C)C=CC(S(O)(=O)=O)=CC=1.O.C(O)C>C1(C)C=CC=CC=1>[NH2:1][C@H:2]1[CH2:8][CH2:7][C:6]2[CH:9]=[CH:10][CH:11]=[CH:12][C:5]=2[N:4]([CH2:13][C:14]([O:16][CH2:17][CH3:18])=[O:15])[C:3]1=[O:21]
5.0 g of tert-butyl (3S)-3-amino-2,3,4,5-tetrahydro-2-oxo-1H-benzazepine-1-acetate (preparation see Example 3E)) and 3.75 g of p-toluenesulfonic acid were boiled in a water separator for 2.5 hours in 80 ml of toluene. A total of 200 ml of ethanol was then added in portions, and the resulting reaction mixture was refluxed for 3.5 hours. The mixture was then concentrated in vacuo, and the residue was taken up with dichloromethane. The mixture was shaken with ice-cold sodium carbonate solution, and the organic phase was washed with water until neutral. The organic phase was dried over sodium sulfate, evaporated in vacuo and the residue which remained was dried. 3.6 g of ethyl (3S)-3-amino-2,3,4,5-tetrahydro-2-oxo-1H-1-benzazepine-1-acetate were obtained, m.p.=106.5°-108° C.; IR: 3350, 3300, 2930, 1735, 1660 cm-1 (film); [α]D20 =-288.4° (c=0.5 in methanol).
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