Benzoyl-leucyl-glycine Ethyl Ester [1, 2]

Abstract

A solution of 2,2’-dipyridyldisulfide [3] (2.20 g, 10 mmol) and benzoyl-l-leucine [1] (2.35 g, 10 mmol) in dichloromethane (60 ml) is stirred at room temperature while a solution of triphenylphosphine (2.62 g, 10 mmol) and glycine ethyl ester (1.04 g, 10 mmol) is added dropwise. After the addition is complete stirring is continued for 30 min. The solution is washed with N HC1 (50 ml), water (50 ml), a 5% solution of NaHCO₃ in water (50 ml) and water (50 ml). It is dried over anhydrous Na₂SO₄ and evaporated to dryness in vacuo. The residue is triturated with light petroleum ether (b.p. 30–50°C), the solid product filtered, washed with petroleum ether and dried. The benzoyldipeptide ester (2.92 g, 91%) melts at 148–152 °C; [α]_D ²⁰°–32.6° (c 3.1, ethanol). This value of specific rotation corresponds [1] to a mixture of 96% l and 4% d isomer.