N-BOC-tyrosine methyl ester (10.0 g, 33.9 mmol) was dissolved in DMF (40 mL) and potassium carbonate (5.62 g, 40.7 mmol) and 4-bromo-1-butene (4.13 mL, 40.7 mmol) were added. The mixture was stirred at rt for 18 h before being diluted with EtOAc (120 mL) and partitioned with 1M hydrochloric acid. The organic phase was washed with hydrochloric acid and then with brine before being dried (MgSO4), filtered and concentrated in vacuo. The crude material was purified by flash chromatography on silica using a gradient of EtOAc and (50/70) petroleum ether to yield a white solid, 3.20 g, 27%. Rf=0.82 (1/2 EtOAc/(50/70) petroleum ether).
