To a solution of (R)—N-naphthalene-2-sulfonyl (3-hydroxy-cyclohepty)glycine ethyl ester (0.90 g, 2.22 mmol) in dichloromethane (30 mL) at 0° C. is added triethylamine (0.463 mL, 3.3 mmol), methane sulfonyl chloride (0.269 g, 2.35 mmol), 4-dimethylaminopyridine (0.015 g, 0.12 mmol), and the reaction is allowed to warm to ambient temperature and stirred for 2 hours. The reaction is diluted with dichloromethane, washed with water and brine, and dried over magnesium sulfate. The solvents are removed in vacuo, and the residue is purified by column chromatography (35% hexanes-ethyl acetate) to afford the title compound as a colorless oil (0.95 g, 88% yield). LCMS (m/z): 484.17 (M+1), 482.16 (M−1).
