[CH2:1]([NH:8][CH2:9][CH2:10][CH2:11][NH:12][CH2:13][C:14]1[CH:19]=[CH:18][CH:17]=[CH:16][CH:15]=1)[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.Br[CH:21]([CH2:26]Br)[C:22]([O:24][CH3:25])=[O:23].C(=O)([O-])[O-].[K+].[K+].CO>CN(C)C=O.C(OCC)(=O)C.O>[CH3:25][O:24][C:22]([CH:21]1[CH2:26][N:12]([CH2:13][C:14]2[CH:15]=[CH:16][CH:17]=[CH:18][CH:19]=2)[CH2:11][CH2:10][CH2:9][N:8]1[CH2:1][C:2]1[CH:3]=[CH:4][CH:5]=[CH:6][CH:7]=1)=[O:23]
N,N′-Dibenzylpropane-1,3-diamine (Sandstroem, J. et al, Tetrahedron; EN; 34; 1978; 371-378) (2.0 g, 7.86 mmol), methyl 2,3-dibromopropionate (1.28 ml, 7.86 mmol), and potassium carbonate (2.17 g, 15.72 mmol) were dissolved in dry dimethylformamide (125 ml) and methanol (20 ml) and the mixture was heated to reflux for 6 days. The reaction mixture was allowed to cool to room temperature and water (200 ml) and ethyl acetate (200 ml) were added. The aqueous layer was extracted with 2×200 ml of ethyl acetate, and the combined organic layers were dried with sodium sulfate, filtered and the solvent was evaporated. The crude product was purified by chromatography on silica, using a mixture of ethyl acetate and heptane 1:6 as the eluent. Fractions containing the product were evaporated, to afford 180 mg of 3A as an clear oil in 7% yield.
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