To a 25 ml pear-shaped flask containing 2-(S-t-butylsulfanylmethyl)-3-(3-bromophenyl)propionic acid (0.22 g, 0.665 mmol) and THF (7 ml), at 0° C. were added dropwise a solution of glycine benzyl ester hydrochloride (0.134 g, 0.665 mmol) and a solution of triethylamine (93 μl, 67.3 mg, 0.665 mmol) in CH2Cl2 (7 ml), followed by dropwise additions of a solution of HOBT (0.102 g, 0.665 mmol) in THF (5 ml) and a solution of 1,3-dicyclohexyl carbodiimide (0.164 g, 0.796 mmol) in CH2Cl2 (6 ml). The ice/water cooling bath was removed and the mixture was stirred at room temperature overnight. After concentration under reduced pressure, the residue was partitioned between water and CH2Cl2, and the combined organic layers were washed with brine, dried over sodium sulfate, filtered, and concentrated under reduced pressure. The crude product was purified by silica gel flash column chromatography eluting with 0 to 50% ether in hexane to give 2-[3-(3-bromophenyl)-2-(S-t-butylsulfanylmethyl)propionylamino]acetic acid benzyl ester as a colorless viscous oil, 0.25 g, 79% yield. HPLC purity: 100%. 1H NMR (CDCl3) δ 1.29 (s, 9H), 2.51 (m, 1H), 2.64 (m, 1H), 2.85 (m, 3H), 4.02 (m, 2H), 5.16 (s, 2H), 5.95 (m, 1H), 7.12 (m, 2H), 7.35 (m, 7H); MS (ES+) [M+H+]: 478, 480; (ES−) [M−H+]: 476, 478.
