Reaction Steps
A solution of sodium hydroxide (NaOH, 20.8 g, 522 mmol) in H2O (125 mL) was added to a suspension of 7 (89.8 g, 174 mmol) in EtOH (400 mL) and stirred for 4 h at room temperature. The solvent was removed and the resulting residue was diluted with H2O (300 mL). The suspension was then treated dropwise with 1M aqueous HCl (522 mmol, 522 mL) to afford a white precipitate, which was subsequently partitioned with EtOAc (1.5 L). The organic layer was then washed with H2O (2×1 L), dried (MgSO4), filtered and concentrated in vacuo to give a white foam (8, 80.2 g, 164 mmol, 95%) as a mixture of two diastereomers: 1H-NMR (400 MHz, (CD3)2SO3) δ=12.01 (s, 1H, 1H′), 11.49 (s, 1H, 1H′), 7.78 (d, J=8.0, 1H), 7.74 (d, J=8.0, 1H′), 7.43 (d, J=8.5, 2H), 7.37 (d, J 8.5, 2H′), 6.96 (d, J=8.5, 2H), 6.93 (d, J=8.5, 2H′), 6.07 (s, 1H′), 5.93 (s, 1H), 5.91 (s, 1H, 1H′), 5.67 (d, J=8.0, 1H), 5.66 (d, J=8.0, 1H′), 5.20-4.81 (m, 2H, 2H′), 4.31 (m, 1H, 1H′), 3.96 (m, 2H, 2H′), 3.62 (m, 2H, 2H′), 2.22 (m, 2H, 2H′), 1.70 (m, 2H, 2H′), 1.54 (m, 2H, 2H′), 1.41 (m, 2H, 2H′); 13C-NMR (400 MHz, (CD3)2SO3) δ=175.3, 175.3, 164.1, 164.0, 160.7, 160.6, 151.2, 151.2, 144.3, 143.7, 129.3 (2C), 129.3 (2C), 128.6, 128.6, 115.1 (2C), 115.0 (2C), 107.6, 103.5, 103.1, 102.8, 93.5, 92.5, 85.9, 85.1, 83.2, 82.8, 82.6, 81.5, 68.3, 68.3, 52.7, 52.5, 34.5, 34.5, 29.2, 29.1, 26.0, 25.9, 25.1, 25.1; IR (film) ν=3354, 3183, 2941, 2101, 1684, 1245, 1069, 1050, 1023, 995, 824; HRMS (MALDI-FTMS) mn/z 510.1600 (510.1595 calculated for C22H25N5O8Na (M+Na)+).
