Reaction Steps
A solution containing Boc-L-valine (352 mg, 1.6 mmol) in NMP (3 mL) was treated with HATU (543 mg, 1.4 mmol) followed by NMM (0.2 mL, 1.8 mmol) at ambient temperature. After 10 min, amine 48 (0.4 g, 1.3 mmol) in NMP (5 mL) was added in a dropwise fashion. After 16 h, the reaction mixture was diluted with diethyl ether and washed successively with NaHCO3, 1 M HCl, water, and brine. The organic extract was dried over anhydrous Na2SO4, filtered and concentrated to afford 630 mg (96%) of 49 which was used without further purification. 1H NMR (CDCl3, 300 MHz) δ7.82-7.79 (m, 1H), 7.38-7.35 (m, 1H), 7.28-7.21 (m, 2H), 5.37 (d, J=9.3 Hz, 1H), 4.50-4.44 (m, 1H), 4.31 (dd, J=6.0, 9.0 Hz, 1H), 4.14 (q, J=6.9 Hz, 2H), 3.72-3.60 (m, 3H), 3.38 (t, J=7.2 Hz, 1H), 3.29 (dd, J=3.0, 13.5 Hz, 1H), 3.12 (app t, J=7.5 Hz, 2H), 2.80-2.74 (m, 4H), 2.46-2.35 (m, 2H), 2.11-1.92 (m, 2H), 1.81-1.73 (m, 1H), 1.69-1.65 (m, 1H), 1.44 (s, 9H), 1.25 (t, J=6.0 Hz, 3H), 1.03 (d, J=6.3 Hz, 3H), 0.96 (d, J=6.6 Hz, 3H) ppm. Mass spectrum: m/z 501 [M+H]+; and, 523 [M+Na]+.
