Reaction Steps
To a solution of 3-naphthalen-2-yl-2-[2-(2-nitrobenzenesulfonylamino)-butyryl amino]-propionic acid methyl ester, 31, (26.6 g, 53.2 mmol) in anhydrous DMF (100 mL) is added 1,2-dibromoethane (100.0 g, 532.0 mmol) and potassium carbonate (66.1 g, 479.0 mmol). The reaction mixture is heated at 60° C. over night. The reaction mixture is cooled in an ice bath and the pH is adjusted to ˜3 with 1M KHSO4. The reaction mixture is extracted with EtOAc (3×300 mL). The organic layers are combined and washed with water (200 mL), dried over Na2SO4 and concentrated in vacuo and the resulting residue is purified over silica (Hexane: EtOAc 1:1; 5% MeOH in EtOAc) to afford 27.4 g (98% yield) of the desired product. 1H NMR (CDCl3, δ): 8.02–7.90 (m, 1H), 7.84–7.70 (m, 3H), 7.64–7.58 (m, 3H), 7.55–7.50 (m, 1H), 7.50–7.40 (m, 2H), 7.30 (d, J=6.0 Hz, 1H), 5.35 (dd, J−12.0, 4.8 Hz, 1H), 4.25 (t, J=7.2 Hz, 1H, 3.78–3.68 (m, 1H), 3.65 (s, 3H), 3.52 (dd, J=15.0, 6.0 Hz, 1H), 3.30–3.10 (m, 4H), 1.58–1.50 (m, 1H), 1.42–1.38 (m, 1H), 0.56 (t, J=7.2 Hz, 3H); 13C NMR, δ 170.5, 167.8, 148.0, 134.2, 134.0, 133.6, 133.1, 132.6, 132.3, 130.9, 128.5, 127.9, 127.7, 127.5, 126.9, 126.5, 126.0, 124.6.
