Reaction Steps
A solution of cyclosporin A (5.0 g, 4.16 mmol), acetic anhydride (3.92 mL, 41.6 mmol), pyridine (3.36 mL, 41.6 mmol), and DMAP (0.5 g, 4.2 mmol) in methylene chloride (20 mL) was stirred overnight at room temperature under N2 atmosphere. Saturated sodium bicarbonate solution (200 mL) was added to the solution and stirred for an additional 2 h. The mixture was extracted with ether, washed with 1 N HCl, neutralized with saturated sodium bicarbonate solution, washed with brine, dried over sodium sulfate, and concentrated in vacuo to afford acetyl cyclosporin A (4.92 g, 95%) as a white solid, which was carried to the next step without further purification: 1H NMR (300 MHz, CDCl3) δ 8.57 (d, J=9.6 Hz, 1H), 8.04 (d, J=6.9 Hz, 1H), 7.51 (d, J=9.4 Hz, 1H), 7.47 (d, J=7.8 Hz, 1H), 5.67 (dd, J=11.0, 4.0 Hz, 1H), 5.60-5.44 (m, 2H), 5.39 (dd, J=11.7, 3.7 Hz, 1H), 5.32-5.13 (m, 4H), 5.06-4.93 (m, 2H), 4.85 (t, J=7.2 Hz, 1H), 4.77 (t, J=9.6 Hz, 1H), 4.65 (d, J=13.7 Hz, 1H), 4.41 (t, J=7.0 Hz, 1H), 3.46 (s, 3H), 3.26 (s, 3H), 3.24 (s, 3H), 3.21 (s, 3H), 3.10 (s, 3H), 2.68 (s, 3H), 2.66 (s, 3H), 2.50-2.35 (m, 1H), 2.25-1.80 (m, 6H), 2.08 (s, 3H), 2.01 (s, 3H), 1.75-1.55 (m, 6H), 1.45-0.75 (m, 55H); ESI MS m/z 1245 [C64H113N11O13+H]+.
