Reaction Steps
Following General Procedure: Method A using (6R,6aS,14aR)-methyl 1,6,8,14a-tetrahydroxy-11-((2S,3R,4R,5R,6S)-4-hydroxy-3,5-dimethoxy-6-methyltetrahydro-2H-pyran-2-ylamino)-6a-methoxy-3-methyl-7,9,12,14-tetraoxo-5,6,6a,7,9,12,14,14a-octahydrobenzo[a]tetracene-2-carboxylate (35 mg, 0.050 mmol), potassium carbonate (21 mg, 0.15 mmol) and benzyl bromoacetate (24 μL, 0.15 mmol), the product was purified by preparative TLC (silica gel, 95:5 dichloromethane/methanol) to afford (6R,6aS,14aR)-methyl 1-(2-(benzyloxy)-2-oxoethoxy)-6,8,14a-trihydroxy-11-((2S,3R,4R,5R,6S)-4-hydroxy-3,5-dimethoxy-6-methyltetrahydro-2H-pyran-2-ylamino)-6a-methoxy-3-methyl-7,9,12,14-tetraoxo-5,6,6a,7,9,12,14,14a-octahydrobenzo[a]tetracene-2-carboxylate (22 mg, 51%) as a brown solid: 1H NMR (500 MHz, CDCl3) δ 14.18 (s, 1H), 8.29 (s, 1H), 7.44-7.31 (m, 5H), 6.88 (d, J=8.7 Hz, 1H), 6.85 (s, 1H), 5.87 (s, 1H), 5.40 (d, J=12.2 Hz, 1H), 5.31 (d, J=12.2 Hz, 1H), 5.00 (s, 1H), 4.95 (dd, J=9.9, 7.3 Hz, 1H), 4.68 (d, J=8.7 Hz, 1H), 4.54 (d, J=15.2 Hz, 1H), 4.48 (br s, 1H), 4.45 (br s, 1H), 3.78 (s, 3H), 3.76-3.71 (m, 1H), 3.69 (d, J=1.6 Hz, 1H), 3.60-3.54 (m, 2H), 3.60 (s, 6H), 3.39 (s, 3H), 3.36-3.32 (m, 1H), 3.13 (t, J=9.2 Hz, 1H), 2.47 (d, J=4.5 Hz, 1H), 2.18 (s, 3H), 1.36 (d, J=6.2 Hz, 3H); MS (ESI+) m/z 846 (M+H); HPLC 94.4% (AUC), tR 18.76 min.
