Reaction Steps
Compound 20 (0.150 g, 0.274 mmol) was treated with trifluoroacetic acid (1.0 mL) in chloroform (10 mL) for 2 h at room temperature. The solvent was removed on a rotary evaporator and the residue was then basified with 2 N NH3 in methanol to get the free amine, which was purified by silica gel column chromatography, eluting with chloroform-methanol, 9.0:1.0, to afford the product 25 (0.092 g, 75%) as a brown solid: mp 215-217° C. IR (KBr) 3075, 1729, 1687, 1673, 1572, 1532, 1433, 1202, 760, 722, 455 cm−1; 1H NMR (DMSO-d6, 300 MHz) δ 10.2 (s, 1H), 8.60 (d, J=1.8 Hz, 1H), 8.47 (d, J=8.7 Hz, 1H), 7.89 (dd, J=1.8, J=8.7 Hz, 1H), 7.74 (m, 3H), 7.54 (m, 2H), 7.47 (m, 1H), 4.53 (t, J=3.2 Hz, 2H), 3.59 (s, 3H), 2.96 (m, 2H), 2.38 (m, 4H), 2.13 (m, 2H), 1.87 (m, 2H); 13C NMR (DMSO-d6, 75 MHz) δ 190.1, 173.0, 171.0, 162.6, 154.4, 138.3, 136.6, 134.2, 134.0, 131.0, 127.1, 125.8, 123.5, 123.4, 122.6, 116.6, 107.4, 79.1, 51.3, 41.2, 38.6, 36.6, 35.2, 32.6, 27.3, 20.2; ESIMS m/z (relative intensity) 448 (MH+, 100); HRESIMS calcd for C25H25N3O5 448.1867 (MH+). found 448.1877 (MH+); HPLC purity: 100% (1% TFA in MeOH—H2O, 70:30).
