Reaction Steps
To a solution of 1-(furan-2-yl)-N-methylmethanamine (195 mg, 1.76 mmol), (S)-3-(biphenyl-4-yl)-2-(tert-butoxycarbonylamino)propanoic acid (500 mg, 1.45 mmol), in CH2Cl2 (3 mL) and DMF (3 mL) was added TEA (0.61 mL, 4.39 mmol) and HATU (724 mg, 1.90 mmol). The mixture was stirred at room temperature for 1 hour. The mixture was quenched with aq. NaHCO3 and extracted with EtOAc. The organic layer was washed with aq. NaHCO3, water, and brine. The organic layer was dried over MgSO4, filtered and concentrated under reduced pressure. The obtained residue was purified by silica gel chromatography using 30%-EtOAc/heptane to 90% EtOAc/heptane to give (S)-tert-butyl 3-(biphenyl-4-yl)-1-((furan-2-ylmethyl)(methyl)amino)-1-oxopropan-2-ylcarbamate (614 mg). HPLC retention time=1.80 minutes (condition B); MS (m+1)=435.1; 1H NMR (400 MHz, CHLOROFORM-d) δ ppm 1.31 (s, 9H, minor rotamer), 1.34 (s, 9H, major rotamer), 2.61 (s, 3H, major rotamer), 2.83 (s, 3H, minor rotamer), 2.87-2.98 (m, 4H), 4.15-4.32 (m, 2H, minor isomer), 4.20 (d, J=15.1 Hz, 1H, major rotamer), 4.62 (d, J=15.1 Hz, 1H, major rotamer), 4.77 (q, J=7.3 Hz, 1H, major rotamer), 4.95 (q, J=7.3 Hz, 1H, minor rotamer), 5.30 (d, J=8.6 Hz, 1H, minor rotamer), 5.39 (d, J=8.6 Hz, 1H, major rotamer), 6.05 (d, J=2.8 Hz, 1H, minor rotamer), 6.10 (d, J=2.8 Hz, 1H, major rotamer), 6.18 (br. s., 1H, minor rotamer), 6.23 (dd, J=3.2, 1.9 Hz, 1H, major rotamer), 7.10-7.50 (m, 18H).
