[Synthesis]
The general procedure for the synthesis of 2,2'-(octadecylimino)diethanol from diethanolamine and stearyl bromide was as follows: in a 500 mL three-necked flask, 10 g (95 mmol) of diethanolamine, 37.96 g (0.114 mol) of octadecyl bromide, 39.33 g (0.285 mol) of potassium bicarbonate, and 0.5 g of potassium iodide were sequentially added, followed by 200 mL of acetonitrile as solvent. The reaction mixture was heated to reflux with stirring and kept for 3 hours. After completion of the reaction, the solvent was removed by rotary evaporator and the residue was dissolved in dichloromethane. The organic phase was washed twice separately with deionized water, dried over anhydrous magnesium sulfate, filtered and the filtrate was concentrated under reduced pressure. The residue was recrystallized with acetone to give 33 g of white crystal product in quantitative yield. The melting point of the product was 49 °C. Thin layer chromatography (TLC) showed an Rf value of 0.20 (unfolding agent was dichloromethane/methanol, 90:10 v/v). Infrared spectroscopy (KBr press) showed a hydroxyl absorption peak at 3310 cm-1 . The NMR hydrogen spectra (200 MHz, CDCl3, with hexamethyldisiloxane as internal standard) chemical shifts δ ppm were 3.53 (triple peak, 4H, J = 5.43 Hz, CH2-O), 3.27 (single peak, 2H, OH), 2.57 (triple peak, 4H, J = 5.43 Hz, N-CH2-CO), 2.44 (triple peak, 2H. J = 7.06 Hz, CH2-N), 1.34 (multiple peaks, 2H, CH2-CN), 1.18 (single peak, 30H, CH2), 0.80 (triple peak, 3H, J = 5.85 Hz, CH3). |