반응 단계
To a mixture of 3-hydroxy-4-methoxypicolinic acid (0.198 g, 1.17 mmol), HATU (0.47 g, 1.25 mmol), and N-methylmorpholine (0.47 g, 4.7 mmol) in CH2Cl2 (9 mL) was added (3S,7S,8R,9S)-3-amino-8-isobutoxy-9-methyl-7-(4-methylbenzyl)-1,5-dioxonan-2-one (272 mg, 0.78 mmol), and the tan mixture was stirred at room temperature for 7 h. The resulting homogeneous solution was adsorbed to Celite® and purified by flash chromatography (SiO2, 0→30% acetone/hexanes) to give 3-hydroxy-N-((3S,7S,8R,9S)-8-isobutoxy-9-methyl-7-(4-methylbenzyl)-2-oxo-1,5-dioxonan-3-yl)-4-methoxypicolinamide (0.30 g, 77%) as a white foam: 1H NMR (400 MHz, CDCl3) δ 11.95 (s, 1H), 8.54 (d, J=8.3 Hz, 1H), 7.97 (d, J=5.2 Hz, 1H), 7.09 (d, J=2.1 Hz, 4H), 6.85 (d, J=5.2 Hz, 1H), 5.01 (m, 2H), 4.02 (dd, J=11.7, 7.3 Hz, 1H), 3.92 (s, 3H), 3.46 (m, 4H), 3.34 (dd, J=8.3, 6.5 Hz, 1H), 3.13 (m, 2H), 2.31 (s, 4H), 1.93 (m, 2H), 1.50 (d, J=6.4 Hz, 3H), 0.96 (d, J=6.7 Hz, 6H); 13C NMR (101 MHz, CDCl3) δ 171.15, 168.90, 155.31, 148.71, 140.62, 136.76, 135.58, 130.20, 129.15, 129.05, 109.56, 84.61, 79.28, 75.92, 72.53, 72.16, 56.08, 51.53, 47.47, 34.60, 29.20, 21.03, 19.50, 18.83; HRMS-ESI (m/z) [M+H]+ calcd for C27H36N2O7, 500.2523. found, 500.2529.
