Cl.Cl.[NH:3]1[CH2:8][CH2:7][NH:6][CH2:5][CH:4]1[C:9]([O:11][CH2:12][CH3:13])=[O:10].C(N(CC)CC)C.[CH3:21][O:22][C:23]1[CH:24]=[C:25]([CH:29]=[C:30]([O:34][CH3:35])[C:31]=1[O:32][CH3:33])[C:26](Cl)=[O:27]>ClCCl>[CH3:35][O:34][C:30]1[CH:29]=[C:25]([CH:24]=[C:23]([O:22][CH3:21])[C:31]=1[O:32][CH3:33])[C:26]([N:6]1[CH2:7][CH2:8][NH:3][CH:4]([C:9]([O:11][CH2:12][CH3:13])=[O:10])[CH2:5]1)=[O:27]To a mixture of ethyl piperazine-2-carboxylate dihydrochloride (2.0 g), triethylamine (1.2 ml) and dichloromethane (40 ml) is added dropwise, under ice-cooling while stirring, a solution of 3,4,5-trimethoxybenzoyl chloride (1.85 g) in dichloromethane (25 ml). The mixture is stirred for one hour, then the reaction mixture is poured into ice-water, followed by extraction with methylene chloride. The organic layer is washed with water, dried and concentrated under reduced pressure. The residue is purified by means of a silica gel column chromatography (eluent : ethyl acetate-acetone-hexane=2:1:2) to afford ethyl 4-(3,4,5-trimethoxybenzoyl)piperazine-2-carboxylate (2.5 g). This product is recrystallized from ethyl acetatehexane to give colorless crystals, m.p. 114-115° C.
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