Reaction Steps
Compound 72 (7.989 g, 26 mmol) was dissolved in aqueous methanol (3:1, 1200 mL) with THF (2-3 drops) to aid solubility. A solution of LiOH (3.12 g, 130 mmol) was added as a solid to the stirring reaction mixture at 0° C. and stirred for 40 minutes. The reaction was allowed to return to room temperature and stirred for 16 hours, at which time TLC (70% Pet ether:EtOAc) revealed complete reaction. Excess methanol and THF were evaporated in vacuo and the remaining solution acidified to pH 2 with conc. HCl, to furnish a colourless precipitate (73), which was collected by filtration and dried (92%). 1H NMR (250 MHz, CDCl3) δ 10.85 (s, 1H, acid OH), 10.80 (s, 1H, carbamate NH), 8.34-8.32 (d, 1H, aromatic H), 8.00 (dd, 1H, J=1.5, 7.9 Hz, aromatic H), 7.70-7.55 (m, 1H, aromatic H), 7.53-7.10 (m, 5H, aromatic coc), 6.75 (d, 1H, J=16 Hz, 3′-H), 6.46 (dt, 1H, J=6.2, 16 Hz, 2′-H), 4.82 (d, 2H, J=6.3 Hz, 1′-H); 13C NMR (62.9 MHz, CDCl3) δ 170.6 (ester carbonyl), 153.2 (CO carbamate), 142.0 (aromatic quat), 137.1 (aromatic quat), 135.1 (methine), 134.5 (alkenic methine), 132.5 (methine), 131.0 (methine), 127.7 (methine), 125.0 (alkenic methine), 122.6 (methine), 119.0 (methine), 116.5 (aromatic quat), 66.5 (methylene Coc). MS m/z 297 (M+. +1), 265, 252, 236, 224, 205, 189, 176, 149, 138, 117.
