Reaction SMILES: [C:1]([O:4][C@H:5]1[C@H:10]([O:11][C:12](=[O:14])[CH3:13])[C@@H:9]([O:15][C:16](=[O:18])[CH3:17])[CH:8](OC(=N)C(Cl)(Cl)Cl)[O:7][C@@H:6]1[CH2:26][O:27][C:28](=[O:30])[CH3:29])(=[O:3])[CH3:2].[OH:31][C:32]1[C:37]2[C@@:38]3([OH:75])[C@@:51]([O:55][CH3:56])([C@H:52]([OH:54])[CH2:53][C:36]=2[CH:35]=[C:34]([CH3:76])[C:33]=1[C:77]([O:79][CH3:80])=[O:78])[C:50](=[O:57])[C:49]1[C:40](=[CH:41][C:42]2[C:43](=[O:73])[C:44]([NH:60][C@@H:61]4[C@H:66]([O:67][CH3:68])[C@H:65]([OH:69])[C@@H:64]([O:70][CH3:71])[C@H:63]([CH3:72])[O:62]4)=[CH:45][C:46](=[O:59])[C:47]=2[C:48]=1[OH:58])[C:39]3=[O:74]>ClCCl>[C:1]([O:4][C@H:5]1[C@H:10]([O:11][C:12](=[O:14])[CH3:13])[C@@H:9]([O:15][C:16](=[O:18])[CH3:17])[C@@H:8]([O:69][C@H:65]2[C@@H:66]([O:67][CH3:68])[C@@H:61]([NH:60][C:44]3[C:43](=[O:73])[C:42]4[CH:41]=[C:40]5[C:49]([C:50](=[O:57])[C@@:51]6([O:55][CH3:56])[C@@:38]([OH:75])([C:39]5=[O:74])[C:37]5[C:32]([OH:31])=[C:33]([C:77]([O:79][CH3:80])=[O:78])[C:34]([CH3:76])=[CH:35][C:36]=5[CH2:53][C@H:52]6[OH:54])=[C:48]([OH:58])[C:47]=4[C:46](=[O:59])[CH:45]=3)[O:62][C@@H:63]([CH3:72])[C@@H:64]2[O:70][CH3:71])[O:7][C@@H:6]1[CH2:26][O:27][C:28](=[O:30])[CH3:29])(=[O:3])[CH3:2]
Reactant: COC(=O)c1c(C)cc2c(c1O)[C@]1(O)C(=O)c3cc4c(c(O)c3C(=O)[C@]1(OC)[C@H](O)C2)C(=O)C=C(N[C@H]1O[C@@H](C)[C@H](OC)[C@@H](O)[C@H]1OC)C4=O
Reactant: CC(=O)OC[C@H]1OC(OC(=N)C(Cl)(Cl)Cl)[C@H](OC(C)=O)[C@@H](OC(C)=O)[C@@H]1OC(C)=O
Solvent: ClCCl
Product: COC(=O)c1c(C)cc2c(c1O)[C@]1(O)C(=O)c3cc4c(c(O)c3C(=O)[C@]1(OC)[C@H](O)C2)C(=O)C=C(N[C@H]1O[C@@H](C)[C@H](OC)[C@@H](O[C@H]2O[C@H](COC(C)=O)[C@@H](OC(C)=O)[C@H](OC(C)=O)[C@H]2OC(C)=O)[C@H]1OC)C4=O
Temperature: 25 °C
Reaction time: 1 h
Yield: 33.1 %

Procedure:
A mixture of (2R,3R,4S,5R)-2-(acetoxymethyl)-6-(2,2,2-trichloro-1-iminoethoxy)-tetrahydro-2H-pyran-3,4,5-triyl triacetate (25 mg, 0.050 mmol), (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) and 4 Å molecular sieves (10 mg) in dichloromethane (1 mL) was stirred at room temperature under nitrogen for 1 h. Then borontrifluoride diethyl etherate (3 μL, 0.02 mmol) was added at −42° C. The reaction mixture was stirred at −42° C. for 4 h, quenched with sodium bicarbonate (20 mg), filtered through diatomaceous earth and concentrated. The crude product was purified by preparative TLC (95:5 dichloromethane/methanol) and semi-preparative HPLC (45:55 acetonitrile/water with 0.05% TFA) to afford (2R,3R,4S,5R,6R)-2-(acetoxymethyl)-6-((2S,3S,4R,5R,6S)-3,5-dimethoxy-2-methyl-6-((6R,6aS,14aR)-1,6,8,14a-tetrahydroxy-6a-methoxy-2-(methoxycarbonyl)-3-methyl-7,9,12,14-tetraoxo-5,6,6a,7,9,12,14,14a-octahydrobenzo[a]tetracen-11-ylamino)tetrahydro-2H-pyran-4-yloxy)tetrahydro-2H-pyran-3,4,5-triyl triacetate (17 mg, 32%) as a red solid: 1H NMR (500 MHz, CDCl3) δ 14.20 (s, 1H), 12.10 (s, 1H), 8.20 (s, 1H), 6.83 (d, J=8.8 Hz, 1H), 6.53 (s, 1H), 5.85 (s, 1H), 5.23 (t, J=9.5 Hz, 1H), 5.22 (br s, 1H), 5.13 (t, J=9.7 Hz, 1H), 5.07 (dd, J=9.3, 8.2 Hz, 1H), 4.96 (d, J=6.4 Hz, 1H), 4.84 (d, J=7.9 Hz, 1H), 4.66 (br s, 1H), 4.62 (d, J=8.8 Hz, 1H), 4.20 (d, J=3.2 Hz, 2H), 3.84 (s, 3H), 3.73 (s, 3H), 3.72-3.64 (m, 3H), 3.56 (dd, J=19.7, 6.7 Hz, 1H), 3.50 (s, 3H), 3.40 (s, 3H), 3.33 (d, J=20.1 Hz, 1H), 3.30-3.25 (m, 1H), 3.17 (t, J=9.3 Hz, 1H), 2.40 (s, 3H), 2.06 (s, 3H), 2.04 (s, 3H), 2.03 (s, 3H), 2.02 (s, 3H), 1.33 (d, J=6.1 Hz, 3H); MS (ESI+) m/z 1028 (M+H); HPLC 97.7% (AUC), tR 19.30 min.