Hydrolysis

Abstract

A solution of N-benzyloxycarbonyl-S-benzyl-l-cysteinyl-l-tyrosine ethyl ester [2, 3] (5.37 g, 10 mmol) in methanol (20 ml) is surrounded by a water bath of room temperature and N NaOH (22 ml) [4] is added with stirring. The mixture is stored at room temperature for two hours [5]. Dilute hydrochloric acid (10 ml, N HC1) is added and the methanol removed in vacuo. The aqueous solution is cooled in an ice-water bath and stirred during acidification to Congo (about 12 ml N HC1). After storage in the cold for two hours, the precipitate is collected on a filter, thoroughly washed with water and dried in air. Recrystallization from ethanol-water affords the dipeptide derivative (4.12 g, 81%) in analytically pure form, melting at 200–202 °C; [α] ²⁰_D −16° (c 4, pyridine).