2-tert-Butoxycarbonylamino-3-(1H-imidazol-4-yl)-propionic acid (25 g, 97.92 mmol), benzyl bromide (17.59 g, 12.2 mL, 0.103 mmol) and potassium carbonate (16.9 g, 0.122 mol) in DMF (250 mL) were stirred overnight under argon. The solvent was removed and the residue taken up into water and CH2Cl2. The organic layer was washed with water and brine, dried and filtered. The solvent was removed and the residue subject to column chromatography (silica gel, 75% EA/PE to afford 3-(1-benzyl-1H-imidazol-4-yl)-2-tert-butoxycarbonylamino-propionic acid benzyl ester (6.79 g, 16%) Rf 0.6, followed by 10% MeOH/EA to afford the title compound (15.832 g, 47%) Rf 0.1). ESMS 346 (M+H+) Mpt 100.5-101.7° C. 1H NMR (500 MHz, CDCl3) δ 1.42 (9H, s), 3.02 (2H, m), 4.51 (1H, m), 5.19 (1H, d, J=12.1 Hz), 5.08 (1H, d, J=12.1 Hz), 5.81 (1H, m), 7.35 (5H, m), 7.47 (1H, s). 13C NMR (CDCl3) δ 28.22, 29.48, 53.67, 66.88, 79.88, 116.23, 126.63, 128.26, 128.45, 133.61, 135.19, 135.39, 155.59, 171.97.
