6-Aminohexanoic Acid → 6-((Phenylsulphonyl)amino)hexanoic acid

Benzenesulfonyl chloride (2.5 ml, 19 mmol) was added to a solution of 6-aminohexanoic acid (1 g, 7.62 mmol) in 2N NaOH (22 ml) and dioxane (3 ml), while stirring at 0° C.-5° C. The mixture was allowed to warm to room temperature and stirred for 1 hour. The reaction mixture was washed with ethyl acetate (50 ml), then acidified to pH 2 with 37% hydrochloric acid and extracted with ethyl acetate (2×50 ml). The combined organic layers were dried over sodium sulfate and concentrated. The residue was triturated with hexane. The solid was collected by filtration and dried under vacuum at 50° C. affording 1.1 g of the title compound (55% yield).