C[O-].[Na+].C(O)(=O)C.[CH:8]([NH2:10])=[NH:9].C[O:12][C:13](=O)[CH:14]([CH2:18][CH2:19][O:20][CH2:21][C:22]1[CH:27]=[CH:26][CH:25]=[CH:24][CH:23]=1)[C:15](=O)[CH3:16].C(O)(=O)C>CO>[CH2:21]([O:20][CH2:19][CH2:18][C:14]1[C:13]([OH:12])=[N:9][CH:8]=[N:10][C:15]=1[CH3:16])[C:22]1[CH:27]=[CH:26][CH:25]=[CH:24][CH:23]=1NaOMe (2.75 g, 50 mmol) is added to a stirred solution of formamidine acetate (25 mmol) in MeOH (75 ml) at room temperature. The mixture is stirred for 15 minutes. 2-(2-Benzyloxy-ethyl)-3-oxo-butyric acid methyl ester (20 mmol) is added and the mixture is stirred at room temperature overnight. Acetic acid (1.5 g, 20 mmol) is added and the solvent is removed in vacuo. Water (30 ml) is added to the residue and the mixture is extracted with 2-butanone (3×30 ml). The combined extracts are washed with brine (40 ml), dried (Na2SO4) and evaporated, to provide a yellow solid (160).
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