Reaction Steps
To a mixture of (3S,6S,7R,8S)-3-(3-hydroxy-4-methoxypicolinamido)-6-methyl-8-(naphthalen-1-ylmethyl)-4-oxo-1,5-dioxonan-7-yl isobutyrate (85 mg, 0.154 mmol) and K2CO3 (42.7 mg, 0.309 mmol) in acetone (2.0 mL) was added bromomethyl acetate (21.2 μL, 0.216 mmol), and the reaction was stirred vigorously at 50° C. under N2 for 1 h. The reaction was cooled to room temperature, diluted with CH2Cl2 (10 mL), filtered, and treated with Celite®. The solvent was removed under reduced pressure and the resulting adsorbed crude material was purified by flash chromatography (SiO2, 0→50% acetone/hexanes) to afford (3S,6S,7R,8S)-3-(3-(acetoxymethoxy)-4-methoxypicolinamido)-6-methyl-8-(naphthalen-1-ylmethyl)-4-oxo-1,5-dioxonan-7-yl isobutyrate (70 mg, 0.112 mmol, 73% yield) as a white powder: mp 58-64° C.; 1H NMR (400 MHz, CDCl3) δ 8.37 (d, J=8.1 Hz, 1H), 8.24 (d, J=5.3 Hz, 1H), 8.02-7.94 (m, 1H), 7.89-7.81 (m, 1H), 7.74 (d, J=8.2 Hz, 1H), 7.56-7.43 (m, 2H), 7.40 (dd, J=8.2, 7.0 Hz, 1H), 7.30 (dd, J=7.1, 1.2 Hz, 1H), 6.92 (d, J=5.4 Hz, 1H), 5.71 (d, J=6.5 Hz, 2H), 5.17-5.06 (m, 3H), 4.04 (dd, J=11.6, 7.4 Hz, 1H), 3.89 (s, 3H), 3.60 (d, J=4.2 Hz, 2H), 3.40 (dd, J=11.7, 7.1 Hz, 1H), 3.23 (dd, J=14.2, 3.1 Hz, 1H), 2.77-2.63 (m, 2H), 2.29 (ddt, J=12.2, 8.1, 3.9 Hz, 1H), 2.04 (s, 3H), 1.39 (d, J=5.6 Hz, 3H), 1.29 (dd, J=7.0, 3.9 Hz, 6H); 13C NMR (101 MHz, CDCl3) δ 176.38, 171.75, 170.27, 163.15, 160.19, 145.74, 143.97, 142.01, 134.75, 133.97, 131.96, 128.95, 127.78, 127.32, 125.99, 125.54, 125.38, 123.50, 109.70, 89.40, 74.18, 72.32, 71.93, 56.18, 51.77, 44.97, 34.38, 32.25, 20.85, 19.14, 19.07, 18.28; HRMS-ESI (m/z) [M+H]+ calcd for C33H39N2O10 expected, 623.2599. found, 623.2611.
