Reaction Steps
A 0.10 M solution of 13b (15.0 mg, 0.0220 mmol) in pyridine (0.220 mL) was cooled to 0° C., and acetic anhydride (10.4 μL, 0.110 mmol) was added. The reaction mixture was allowed to warm to rt over 2 h and was stirred at rt for 24 h. The reaction mixture was then cooled to 0° C., and a 1:1 mixture of dioxane/water (0.630 mL) was added. The mixture was allowed to warm to rt and was stirred for 12 h at rt. The solvent was removed under reduced pressure. Column chromatography (100:0 to 90:10 CH2Cl2:MeOH) afforded 13.0 mg (81%) of 3 as an amorphous solid. [α]D23=+24.3 (c=0.7, MeOH). IR: 1371, 1420, 1497, 1544, 1667, 1741, 2342, 2360, 2840, 2872, 2929, 2961, 3293, 3368 cm−1. 1H NMR (500 MHz, MeOD): δ 0.79 (d, 3H, J=6.7 Hz), 0.85 (d, 3H, J=6.9 Hz), 0.87-0.92 (m, 6H), 0.96 (d, 3H, J=6.6 Hz), 1.05 (d, 3H, J=6.3 Hz), 1.15-1.23 (m, 1H), 1.35-1.42 (m, 1H), 1.57-1.65 (m, 3H), 1.69-1.72 (m, 1H), 1.77-1.81 (m, 1H), 1.84-1.93 (m, 4H), 1.95-2.01 (m, 2H), 2.08-2.18 (m, 2H), 2.13 (s, 3H), 2.28-2.39 (m, 4H), 2.33 (s, 3H), 2.48-2.53 (m, 1H), 2.94 (app d, 1H, J=10.1 Hz), 3.08 (app d, 1H, J=11.3 Hz), 3.40-3.43 (m, 2H), 4.41 (br s, 1H), 4.60 (d, 1H, J=9.5 Hz), 5.40 (d, 1H, J=12.4 Hz), 5.87 (d, 1H, J=10.8 Hz), 6.13 (d, 1H, J=10.8 Hz), 8.18 (s, 1H). 13C NMR (125 MHz, MeOD) δ 10.7, 16.4, 20.3, 20.70, 20.76, 22.73, 22.74, 23.7, 25.54, 22.56, 26.7, 26.9, 31.1, 32.2, 34.7, 35.9, 37.4, 40.2, 44.18, 44.25, 55.2, 56.5, 69.7, 70.7, 125.6, 150.8, 163.2, 170.7, 171.9, 173.3, 173.8, 176.4, 180.5. HRMS (FAB) calcd for C35H58N5O9S (M+H): 724.3955. Found: 724.3937.
