Reaction Steps
To a stirred solution of 3A (836 mg, 1.11 mmol) in CH3CN/CH2Cl2 (1:1, 60 mL) at RT was added Et2NH (3 mL). After stirring for 3 h at RT the reaction mixture was diluted with heptane (60 mL) and concentrated to give the crude amine as a colourless oil. To a stirred solution of Fmoc-D-valine (577 mg, 1.7 mmol) in CH2Cl2 (40 mL) was added EDAC.HCl (326 mg, 1.7 mmol), HOBt (230 mg, 1.7 mmol) and DIEA (627 μl, 3.6 mmol). After stirring at RT for 10 minutes a solution of the crude amine in CH2Cl2 (20 mL) was then added and the reaction mixture stirred for 12 h. Whereupon the reaction was washed with water (15 mL), 10% HCl (15 mL), 5% NaHCO3 (15 mL) and sat NaCl (15 mL) solutions, dried (Na2SO4), filtered, and the solvent removed to give an off white solid which was recrystallised from CH3CN to give 4C as a white solid (734 mg, 0.86 mmol, 78%): 1H-NMR (400 MHz, CDCl3) δ 7.74 (d, J=7.5 Hz, 2H), 7.53 (t, J=7.5 Hz, 2H), 7.42-7.32 (m, 9H), 7.30-7.19 (m, 9H), 7.16 (t, J=7.0 Hz, 2H), 6.80 (d, J=8.0 Hz, 1H), 6.57 (d, J=7.0 Hz, 1H), 5.52 (d, J=8.0 Hz, 1H), 4.44 (t, J=8.0 Hz, 1H), 4.38 (dd, J=10.5, 7.5 Hz, 1H), 4.25 (dd, J=10.5, 7.0 Hz, 1H), 4.17-3.95 (m, 3H), 3.87 (dd, J=18.1, 5.5 Hz, 1H), 3.78 (dd, J=18.1, 5.5 Hz, 1H), 3.63 (s, 3H), 2.71 (dd, J=12.5, 6.0 Hz, 1H), 2.53 (dd, J=12.5, 6.0 Hz, 1H), 2.21 (sept, J=6.4 Hz, 1H), 2.07-1.93 (m, 1H), 0.93-0.83 (m, 12H); 13C NMR 100 MHz 171.5 (C), 171.1 (C), 170.2 (2×C), 156.6 (C), 144.4 (C), 144.0 (C), 143.8 (C), 141.4 (C), 129.6 (CH), 128.3 (CH), 127.9 (CH), 127.2 (CH), 127.1 (CH), 125.2 (CH), 120.1 (CH), 67.3 (CH2), 67.2 (C), 60.3 (CH), 58.5 (CH), 52.5 (CH), 52.3 (CH), 47.3 (CH), 41.0 (CH2), 33.8 (CH2), 31.5 (CH), 30.5 (CH), 19.2 (2×CH3), 18.0 (CH3), 17.8 (CH3); LRMS (ES+) m/z 1832 (10%, [2M+Na]+), 877.5 (100%, [M+Na]+).
