A solution of N-hexyl-6-hydroxyhexanamide (2.8 g, 13 mmol) and triethylamine (2.8 g, 28 mmol) in anhydrous THF (45 ml) was stirred under argon atmosphere at 0°C. Methanesulfonyl chloride (3.5 g, 28 mmol) was added dropwise. The mixture was stirred at room temperature for 30 min, poured in iced water (100 ml) and extracted with DCM. The organic phase was dried with MgSO4, filtered and concentrated under reduced pressure. The desired compound was purified by column chromatography (ethyl acetate) and dried under reduced pressure as a white solid (3.1 g, 82%).