Reaction Steps
Compound 19 (0.060 g, 0.112 mmol) was treated with trifluoroacetic acid (0.5 mL) in chloroform (5 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 in methanol to get the free amine, which was purified by silica gel column chromatography, eluting with chloroform-methanol, 8.8:1.2, to yield the product 24 (0.028 g, 60%) as a brown solid: mp 272-274° C. IR (KBr) 2952, 1735, 1690, 1656, 1572, 1532, 1510, 1160, 765, 455 cm−1; 1H NMR (CD3OD, 300 MHz) δ 8.28 (s, 1 H), 7.92 (m, 1 H), 7.31 (m, 3 H), 7.20 (s, 2 H), 4.30 (t, J=4.8 Hz, 2H), 3.71 (s, 3 H), 2.83 (m, 2 H), 2.68 (m, 4 H), 2.00 (m, 2 H); 13C NMR (CD3OD, 125 MHz) δ 191.8, 174.9, 172.6, 164.4, 155.6, 139.2, 138.2, 135.9, 134.8, 131.9, 129.3, 127.1, 125.0, 124.9, 124.0, 123.8, 122.9, 118.5, 114.8, 109.5, 57.6, 57.4, 57.2, 43.6, 36.3, 32.2, 30.3, 29.7; ESIMS m/z (relative intensity) 434 (MH+, 100); HRESIMS calcd for C24H23N3O5 434.1852 (MH+), found 434.1835 (MH+); HPLC purity: 98.0% (1% TFA in MeOH).
