Reaction Steps
To a solution of (3S,6S,7R,8S)-3-(3-hydroxy-4-methoxypicolinamido)-6-methyl-8-(naphthalen-1-ylmethyl)-4-oxo-1,5-dioxonan-7-yl isobutyrate (80 mg, 0.145 mmol) and DMAP (28.4 mg, 0.232 mmol) in CH2Cl2 (1.45 mL) was added acetyl chloride (218 μL, 0.218 mmol) slowly and the resulting mixture was stirred at room temperature for 14 h. The reaction mixture was treated with Celite®, the solvent removed under reduced pressure, and the resulting adsorbed crude material was purified by flash chromatography (SiO2, 0→100% acetone/hexanes) to afford (3S,6S,7R,8S)-3-(3-acetoxy-4-methoxypicolinamido)-6-methyl-8-(naphthalen-1-ylmethyl)-4-oxo-1,5-dioxonan-7-yl isobutyrate as a white powder (80 mg, 93%): mp 104-108° C.; 1H NMR (400 MHz, CDCl3) δ 8.53 (d, J=8.2 Hz, 1H), 8.27 (d, J=5.4 Hz, 1H), 8.01-7.94 (m, 1H), 7.88-7.81 (m, 1H), 7.73 (d, J=8.2 Hz, 1H), 7.55-7.43 (m, 2H), 7.39 (dd, J=8.2, 7.0 Hz, 1H), 7.29 (dd, J=7.0, 1.2 Hz, 1H), 6.96 (d, J=5.4 Hz, 1H), 5.18-5.02 (m, 3H), 4.00 (dd, J=11.7, 7.4 Hz, 1H), 3.86 (s, 3H), 3.58 (d, J=4.2 Hz, 2H), 3.37 (dd, J=11.7, 7.2 Hz, 1H), 3.22 (dd, J=14.1, 3.1 Hz, 1H), 2.76-2.63 (m, 2H), 2.38 (s, 3H), 2.34-2.22 (m, 1H), 1.38 (d, J=5.7 Hz, 3H), 1.29 (d, J=3.7 Hz, 3H), 1.27 (d, J=3.7 Hz, 3H); 13C NMR (101 MHz, CDCl3) δ 176.38, 171.66, 168.84, 162.67, 159.42, 146.73, 141.03, 137.53, 134.77, 133.99, 131.98, 128.97, 127.78, 127.34, 126.01, 125.57, 125.39, 123.50, 109.95, 77.05, 74.20, 72.26, 71.84, 56.29, 51.51, 44.99, 34.38, 32.26, 20.73, 19.15, 19.08, 18.28; HRMS-ESI (m/z) [M+H]+ calcd for C32H37N2O9 expected, 593.2494. found, 593.2502.
