Reaction Steps
To a mixture of (3R,7S,8S,9R)-3-amino-7,8-bis(benzyloxy)-9-methyl-1,5-dioxonan-2-one hydrochloride (85.0 mg, 0.2015 mmol) and 3-hydroxy-4-methoxypicolinic acid (54.0 mg, 0.321 mmol) in DCM (1.20 mL) was added 4-methylmorpholine (0.141 mL, 1.29 mmol) followed by HATU (135.0 mg, 0.343 mmol) and the mixture was stirred at room temperature for 4 h. The reaction mixture was directly purified by flash chromatography (SiO2, hexanes/EtOAc gradient) to yield the title compound as a colorless oil (65.4 mg, 61%): IR (neat) 3368, 2933, 1748, 1648, 1527, 1242, 1066 cm−1; 1H NMR (400 MHz, CDCl3) δ 11.98 (s, 1H), 8.86 (d, J=8.0 Hz, 1H), 8.01 (d, J=5.2 Hz, 1H), 7.41-7.27 (m, 10H), 6.86 (d, J=5.2 Hz, 1H), 5.36 (qd, J=6.7, 3.1 Hz, 1H), 5.06 (ddd, J=8.0, 6.1, 1.9 Hz, 1H), 4.71 (d, J=11.4 Hz, 1H), 4.68 (d, J=11.8 Hz, 1H), 4.60 (d, J=11.3 Hz, 1H), 4.58 (d, J=11.8 Hz, 1H), 4.16 (dd, J=12.2, 3.6 Hz, 1H), 4.12 (dd, J=9.4, 2.2 Hz, 2H), 3.98 (dd, J=11.7, 6.1 Hz, 1H), 3.94 (s, 3H), 3.71 (dd, J=11.9, 1.7 Hz, 1H), 3.57-3.50 (m, 1H), 1.38 (d, J=6.8 Hz, 3H); 13C NMR (101 MHz, CDCl3) δ 169.86, 169.07, 155.41, 148.82, 140.81, 138.27, 138.10, 130.51, 128.58, 128.54, 128.14, 128.05, 128.00, 127.85, 109.64, 78.70, 75.15, 74.37, 72.35, 71.55, 56.21, 53.37, 15.28; HRMS-ESI (m/z) [M]+ calcd for C29H32N2O8, 536.2159; found, 536.2162.
