Reaction Steps
Compound 21 (0.030 g, 0.053 mmol) was treated with trifluoroacetic acid (0.25 mL) in chloroform (3 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, 9.2:0.8, to yield the product 26 (0.015 g, 55%) as a red solid: mp 153-155° C. IR (KBr) 2947, 1739, 1705, 1693, 1661, 1570, 1530, 1431, 1197, 760, 665 cm−1; 1H NMR (CD3OD, 300 MHz) δ 8.51 (d, J=2.4 Hz, 1H), 8.34 (d, J=9.0 Hz, 1H), 7.70 (dd, J=2.4, J=9.0 Hz, 1H), 7.60 (t, J=9.0 Hz, 1H), 7.51 (m, 2H), 7.31 (m, 1H), 4.55 (t, J=4.5 Hz, 2H), 3.67 (s, 3H), 3.13 (m, 2H), 2.39 (m, 4H), 2.26 (m, 2H), 1.70 (m, 2H); 13C NMR (DMSO-d6, 125 MHz) δ 190.0, 173.3, 171.3, 162.3, 154.4, 138.3, 136.6, 134.2, 133.9, 130.9, 127.0, 125.6, 123.5, 123.4, 123.3, 122.5, 116.5, 107.2, 51.2, 42.1, 38.2, 36.0, 33.0, 30.9, 24.4, 24.0; ESIMS (m/z, relative intensity) 462 (MH+, 100); HRESIMS calcd for C26H27N3O5 462.2023 (MH+). found 462.2031 (MH+); HPLC purity: 98.5% (1% TFA in MeOH—H2O, 70:30).
