General procedure: A dichloromethane solution (10 mL/mmol) of 1,8-diamino-3,6-dioxaoctane (1 eq.) was treated with di-tert-butyl dicarbonate (0.15 eq.) at 0 °C, kept at 0 °C for 5 hours, and then the reaction was continued at room temperature for 18 hours. Upon completion of the reaction, the organic phase was washed with water until all unreacted 1,8-diamino-3,6-dioxaoctane was removed by extraction. The organic phase was dried over anhydrous magnesium sulfate and recovered quantitatively to give the Boc-protected product tert-butyl 2-(2-(2-aminoethoxy)ethoxy)ethylcarbamate, which was concentrated under vacuum. The product characterization data were as follows:11a: 1H NMR (300 MHz, CDCl3): δ 1.45 (s, 9H), 1.80 (br m, 2H, NH2), 3.25 (m, 2H), 3.38 (m, 2H), 3.50-3.70 (m, 8H), 5.10 (br s, 1H, NHCO2).11b: 1H NMR ( 300 MHz, CDCl3): δ 1.42 (s, 9H), 1.75 (br m, 2H, NH2), 2.84 (t, 2H, J = 5.3 Hz), 3.29 (m, 2H), 3.51 (m, 4H), 3.58 (sharp m, 8H), 5.30 (br s, 1H, NHCO2).
