A EDC.HCl (249 mg, 1.3 mmol) was added to a stirred colorless solution of azido-Thr-OMe.HCl (4) (195 mg, 1.0 mmol), HOBT (158 mg, 1.0 mmol), 4′-Ethyl-biphenyl-4-carboxylic acid (5) (226 mg, 1.0 mmol) and DIEA (0.44 ml, 2.5 mmol) in DCM (10 ml) at rt under N2. After 24 h, the reaction had reached completion by TLC (Hexane/EtOAc (60:40) (Rf=0.3)) and LCMS. The reaction was evaporated under reduced pressure to a brown tar. The crude product was dissolved in EtOAc (100 ml) and washed with 0.2N aq. HCl (2×50 ml), aq. sat. NaHCO3 (50 ml), brine (50 ml), dried (Na2SO4), filtered and concentrated under reduced pressure to yield a crude brown solid. The crude material was further purified by column chromatography eluting with Hexane/EtOAc (70:30) giving 245 mg (67% yield) of pure product after evaporation and drying in vacuo.
