DIEA (10.5 ml, 60.3 mmol) was added to a stirred solution of 4-[4-Amino-phenyl)-buta-1,3-diynyl]-benzoic acid (1) (5.0 g, 19.1 mmol), HOBT (2.72 g, 20.1 mmol), EDC (3.85 g, 20.1 mmol) in DMF (80 ml). After 2 min., the H-DAP(Boc)-OMe was added in one portion. After 12 hours at rt, the reaction was found complete by LCMS. The reaction was diluted with EtOAc/hexane (4:1) (500 ml). The organic phase was washed with 1N NaOH (2×80 ml), water (2×80 ml), sat. brine (80 ml), dried with Na2SO4, filtered and concentrated under reduced pressure to give crude product. The residue was filtered through a filter plug of silica eluting with EtOAc/hexane (4:1). The fractions with product were evaporated to give 8.02 g of product in 91% yield.
