Trans 3-(acetylthiomethyl)-2-oxo-1-azacyclodecane-10-carboxylic acid (0.15 g, 0.52 mmol) is dissolved in dimethylformamide (2.5 mL). Benzyl bromide (0.062 mL, 0.52 mmol) and cesium carbonate (0.085 g, 0.26 mmol) are added, and the reaction is stirred at room temperature overnight. The reaction is diluted with water, and the aqueous layer is extracted several times with methylene chloride. The combined organic layers are dried (MgSO4), and the solvent is evaporated. The product is purified by silica gel chromatography (10% ethyl acetate/hexane) to give trans benzyl 3-(acetylthiomethyl)-2-oxo-1-aza-cyclodecane-10-carboxylate m.p. 117°-118° C.
