Reaction Steps
A 25 mL screw top vial was charged with (3S,7R,8R,9S)-9-methyl-7-(4-methylbenzyl)-2-oxo-8-phenoxyoxonan-3-aminium chloride (259 mg, 0.642 mmol), 3-hydroxy-4-methoxypicolinic acid (122 mg, 0.721 mmol), anhydrous CH2Cl2 (6.5 mL), and N,N-diisopropylethylamine (340 μL, 1.95 mmol). To the mixture was added PyBOP (376 mg, 0.723 mmol) and the reaction was stirred at room temperature for 1.5 h and then directly purified by column chromatography on SiO2 (2→30% acetone/hexanes) to provide the title compound as a white solid (162 mg, 49%): mp 62-66° C.; 1H NMR (400 MHz, CDCl3) δ 12.09 (s, 1H), 8.48 (d, J=8.2 Hz, 1H), 7.98 (d, J=5.1 Hz, 1H), 7.37-7.28 (m, 2H), 7.12-6.93 (m, 7H), 6.86 (d, J=5.2 Hz, 1H), 5.14 (dq, J=9.2, 6.4 Hz, 1H), 4.62 (dt, J=10.9, 7.4 Hz, 1H), 4.35 (t, J=8.9 Hz, 1H), 3.93 (s, 3H), 2.99 (dd, J=13.3, 3.2 Hz, 1H), 2.42-2.26 (m, 5H), 2.16-2.04 (m, 1H), 1.79-1.52 (m, 3H), 1.41-1.23 (m, 4H), 1.08-0.98 (m, 1H); 13C NMR (101 MHz, CDCl3) δ 172.06, 168.59, 159.58, 155.27, 148.66, 140.47, 136.92, 135.38, 130.28, 129.63, 128.98, 128.59, 121.16, 115.48, 109.43, 81.02, 74.89, 55.99, 51.43, 45.59, 36.34, 33.47, 26.57, 20.95, 18.78, 18.33; ESIMS: m/z 519 ([M+H]+).
