Reaction Steps
H-Phe(4-CH2NHBoc)-Leu-OMe 80 (68 mg, 161 μmol, 1 equiv.) was dissolved in DCM (5 ml) and N3-Phe-OH (37 mg, 193 μmol, 1.2 equiv.), HBTU (79 mg, 209 μmol, 1.3 equiv.) and DiPEA (67 μl, 403 μmol, 2.5 equiv.) were added and the mixture was stirred for 90 minutes before being washed with 1M HCl (2×), sat aq. NaHCO3 (3×) and dried over Na2SO4. Column chromatography (10% EA:tol->35% EA:tol) yielded the title compound (71 mg, 119 μmol, 74%). 1H NMR (400 MHz, CDCl3): δ ppm 7.40-7.20 (m, 5H), 7.17 (d, J=7.8 Hz, 2H), 7.04 (d, J=7.9 Hz, 2H), 6.97 (d, J=8.1 Hz, 1H), 6.34 (d, J=7.5 Hz, 1H), 4.93 (s, 1H), 4.67 (dd, J=14.3, 7.1 Hz, 1H), 4.51 (td, J=8.2, 5.4 Hz, 1H), 4.26 (d, J=5.2 Hz, 2H), 4.16 (dd, J=8.2, 4.2 Hz, 1H), 3.70 (s, 3H), 3.24 (dd, J=14.1, 4.1 Hz, 1H), 3.08-2.82 (m, 3H), 1.62-1.46 (m, 3H), 1.45 (s, 9H), 0.88 (d, J=6.1 Hz, 6H). 13C NMR (101 MHz, CDCl3): δ ppm 172.71, 169.82, 168.38, 155.80, 137.63, 135.83, 135.00, 129.51, 129.42, 128.60, 127.81, 127.24, 79.36, 65.13, 54.03, 52.25, 50.80, 44.37, 41.36, 38.33, 37.89, 28.33, 24.70, 22.58, 21.91.
