In a round bottom flask, 0.99 g (3 mmol) of 16-bromohexadecanoic acid was dissolved in 15 mL (15 mmol) of thionyl chloride. The solution was heated at reflux for 30 minutes. Thionyl chloride was removed under reduced pressure, at 40° C. The residue was dissolved in 30 mL of dichloromethane. To this solution, 1.11 g (3.1 mmol) of 4,7,13,16-tetraoxa-1,10,21-triaza-bicyclo[8.8.5]tricosane-19,23-dione and 1.4 mL (7.7 mmol) of DIPEA were added. The mixture was stirred at room temperature for 1 day. DIPEA and solvent were removed from the solution by evaporation of the solvent mixture under reduced pressure, and the residue was redissolved in 100 mL of dichloromethane. The solution was washed three times with 100 mL of 2 N HCl, once with 100 mL of water, and finally dried over anhydrous MgSO4. The solvent was removed under reduced pressure and the product was finally purified by column chromatography (CH2Cl2:CH3OH 20:1) to afford a yellow oil. Yield: 0.96 g (72%). Rf:0.32 (CH2Cl2:CH3OH 20:1), 1H-NMR (400 MHz, CDCl3): δ 1.24-1.42 (m, 22H), 1.65-1.67 (m, 2H), 1.82-1.89 (m, 2H), 2.38-2.42 (dd, J=15.41, 7.58 Hz, 2H), 2.66-2.83 (m, 2H), 2.97-3.05 (m, 2H), 3.41 (t, J=6.82, 2H), 3.47-3.72 (m, 16H), 3.82-3.99 (m, 4H), 4.22-4.40 (m, 4H). 13C-NMR (100 MHz, CDCl3): δ 25.5 (CH2), 28.5 (CH2), 29.1 (CH2), 29.8 (CH2), 29.8 (CH2), 29.9 (CH2), 30.0 (CH2), 33.1 (CH2), 33.2 (CH2), 34.5 (CH2), 45.8 (CH2), 48.7 (CH2), 49.6 (CH2), 50.3 (CH2), 50.8 (CH2), 50.8 (CH2), 67.3 (CH2), 67.8 (CH2), 70.3 (CH2), 70.9 (CH2), 71.1 (CH2), 71.3 (CH2), 71.8 (CH2), 72.6 (CH2), 168.9 (C═O), 169.5 (C═O), 174.5 (C═O).
