N-(tert-Butoxycarbonyl)-1,5-diaminopentane → Tert-butyl (5-((2-chloroethyl)sulfonamido)pentyl)carbamate

To a stirred solution of 5-(tert-butoxycarbonylamino)pentylamine (1.00 g, 4.94 mmol) and triethylamine (689 μL g, 4.94 mmol) in dichloromethane (22 mL) at 0° C. was added 2-chloro-1-ethanesulfonyl chloride (470 μL, 4.50 mmol). The reaction mixture was stirred for 2 h at room temperature and then washed with saturated aqueous sodium bicarbonate solution (15 mL). The organic layer was dried (Na2SO4) and the solvent was removed under reduced pressure to give the title compound (100% yield), which was used in the next step without further purification.