To a solution of Intermediate 1 (0.2 g, 0.81 mmol) in 40 mL of DCM were added Et3N (0.13 mL, 1.1 equiv.). DCC (0.18 g, 1.1 equiv.), HOBT (0.12 g, 1.1 equiv.) and (E)-3-(4-acetylaminophenyl)acrylic acid (0.18 g, 1.1 equiv.). After 24 hours of stirring at rt the reaction was judged to be completed by tlc monitoring (SiO2, DCM:MeOH 95:5) and was quenched with 150 mL of water. A white solid precipitated out and was filtered off. The filtrate was extracted with DCM, washed with brine (5 mL), dried over MgSO4 and concentrated in vacuo. Flash chromatography on a 2.5×25 cm3 column of silica gel using DCM:MeOH (98:2) as eluting solvent and removal of the solvent in vacuo gave the title compound (0.18 g, 51%) as yellow crystals after recrystallization from 2-propanol:pentane.
