[CH2:1]([O:3][C:4](=[O:15])[CH2:5][CH:6]([NH2:14])[C:7]1[CH:12]=[CH:11][C:10]([Cl:13])=[CH:9][CH:8]=1)[CH3:2].[CH3:16][CH:17]([CH3:25])[C:18](=O)[CH2:19][C:20]([O:22][CH3:23])=[O:21].C(O)(=O)C.O>C1C=CC=CC=1>[Cl:13][C:10]1[CH:9]=[CH:8][C:7]([CH:6]([NH:14][C:18]([CH:17]([CH3:25])[CH3:16])=[CH:19][C:20]([O:22][CH3:23])=[O:21])[CH2:5][C:4]([O:3][CH2:1][CH3:2])=[O:15])=[CH:12][CH:11]=15.70 g (25.0 mmol) of ethyl-3-amino-3-(4-chlorophenyl)propanoate [V. Wehner et al., Synthesis 14, 2023-2036 (2002)], 3.993 ml (27.5 mmol) of methyl 4-methyl-3-oxopentanoate and 2.87 ml (50.1 mmol) of acetic acid were taken up in 70 ml of benzene and reacted at reflux on a water separator overnight. After cooling, the mixture was washed with saturated aqueous sodium bicarbonate solution, the organic phase was dried with magnesium sulfate and the solvent was destilled off under reduced pressure. This gave 8.57 g (68% of theory) of the target compound in a purity of 70%. The fraction was used without further work-up for the subsequent steps.
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