Reaction Steps
A mixture of the 4′-(benzyloxy)-3-(benzyloxycarbonyl butylcarbonyloxy) flavone (400 mg, 0.711 mmol) and Pd(OH)2 (56 mg) in THF (10 mL), ethanol (1.2 mL) and AcOH (100 μL) was treated with hydrogen (50 psi) for 18 h. The reaction mixture was then filtered (Celite) and the pad washed with THF. The filtrate was concentrated and the solid residue was purified by flash chromatography (70% THF/toluene+1% AcOH) and the resultant solid recrystallised from THF/petrol to afford the acid as a colourless solid (150 mg, 55%); mp 177-180° C.; 1H NMR (500 MHz, d6-DMSO) δ 1.56-1.66 (m, 4H, CH2CH2), 2.25 (t, 2H, J=7.0 Hz, CH2CO), 2.64 (t, 2H, J=7.0 Hz, CH2CO), 6.96 (app. d, 2H, J=8.5 Hz, H2′,6′), 7.52 (t, 1H, J6,7=J7,8=7.5 Hz, H7), 7.80 (app. d, 2H, J=7.5 Hz, H3′,5′), 7.78 (m, 1H, H8), 7.85 (t, 1H, J5,6=J6,7=7.5 Hz, H6), 8.06 (d, 1H, J5,6=8.0 Hz, H5); 13C NMR (125 MHz, d6-DMSO) δ 23.8, 23.9, 32.9, 33.3 (4C, CH2), 115.9, 118.5, 119.7, 122.7, 125.0, 125.6, 130.1, 131.9, 134.5, 154.9, 155.8 160.6 (Ar), 170.4 170.9, 174.3 (3C, C═O); IR 3257, 2944, 2869, 1765, 1706, 1595, 854 cm−1; HRMS (ESI+) m/z 383.1123, C21H19O7 [M+H]+ requires 383.1131.
