Trans 3-(acetylthiomethyl)-2-oxo-1-azacyclodecane-10-carboxylic acid (0.15 g, 0.52 mmol), 1-acetoxy-2-aminoethane hydrochloride (0.073 g, 0.52 mmol), 1-hydroxybenzotriazole (0.12 g, 0.52 mmol), and 4-methylmorpholine (0.17 mL, 1.56 mmol) are dissolved in methylene chloride (3.0 mL), and the reaction is cooled to 0° C. To this solution is added N-(dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (0.20 g, 1.04 mmol), and the reaction is allowed to warm up to room temperature and then stirred overnight. The reaction is diluted with more methylene chloride, and the organic layer is washed with 1N hydrochloric acid, saturated sodium bicarbonate, dried (MgSO4), and the solvent is evaporated. The product is purified by silica gel chromatography (75% ethyl acetate/hexane) to give 2-acetoxy-N-[[trans 3-(acetylthiomethyl)-2-oxo-1-azacyclodecan-10-yl]-carbonyl]-ethylamine, MS: M+1=373.
